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Documentation: Refactor and switch to Sphinx

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[![Documentation](https://readthedocs.org/projects/restic/badge/?version=latest)](https://restic.readthedocs.io/en/latest/?badge=latest)
[![Build Status](https://travis-ci.org/restic/restic.svg?branch=master)](https://travis-ci.org/restic/restic)
[![Build status](https://ci.appveyor.com/api/projects/status/nuy4lfbgfbytw92q/branch/master?svg=true)](https://ci.appveyor.com/project/fd0/restic/branch/master)
[![Report Card](http://goreportcard.com/badge/github.com/restic/restic)](http://goreportcard.com/report/github.com/restic/restic)
Introduction
============
restic is a backup program that is fast, efficient and secure. Detailed
information can be found in [the documentation](doc/index.md) and [the user
manual](doc/Manual.md). The [design document](doc/Design.md) lists the
technical background and gives detailed information about the structure of the
repository and the data saved therein. The file [FAQ.md](doc/FAQ.md) lists the
most frequently asked questions.
The latest documentation can be viewed online at
<https://restic.readthedocs.io/en/latest>. On the bottom left corner there is
a menu that allows switching to the documentation and user manual for the
latest released version.
News
====
You can follow the restic project on Twitter
[@resticbackup](https://twitter.com/resticbackup) or by subscribing to the
[development blog](https://restic.github.io/blog/).
Install restic
==============
You can download the latest pre-compiled binary from the [restic release page](https://github.com/restic/restic/releases/latest).
Build restic
============
Install Go/Golang (at least version 1.7), then run `go run build.go`,
afterwards you'll find the binary in the current directory:
$ go run build.go
$ ./restic --help
Usage:
restic [OPTIONS] <command>
[...]
You can easily cross-compile restic for all supported platforms, just supply
the target OS and platform via the command-line options like this (for Windows
and FreeBSD respectively):
$ go run build.go --goos windows --goarch amd64
$ go run build.go --goos freebsd --goarch 386
The resulting binary is statically linked and does not require any libraries.
More documentation can be found in the [user manual](doc/Manual.md).
At the moment, the only tested compiler for restic is the official Go compiler.
Building restic with gccgo may work, but is not supported.
Contribute and Documentation
============================
Contributions are welcome! Please **open an issue first** (or add a comment to
an existing issue) if you plan to work on any code or add a new feature. This
way, duplicate work is prevented and we can discuss your ideas and design
first.
More information and a description of the development environment can be found
in [`CONTRIBUTING.md`](CONTRIBUTING.md). A document describing the design of
restic and the data structures stored on the back end is contained in
[`doc/Design.md`](doc/Design.md).
If you'd like to start contributing to restic, but don't know exactly what do
to, have a look at this great article by Dave Cheney:
[Suggestions for contributing to an Open Source project](http://dave.cheney.net/2016/03/12/suggestions-for-contributing-to-an-open-source-project)
A few issues have been tagged with the label `help wanted`, you can start
looking at those: https://github.com/restic/restic/labels/help%20wanted
Contact
=======
If you discover a bug, find something surprising or if you would like to
discuss or ask something, please [open a github issue](https://github.com/restic/restic/issues/new).
If you would like to chat about restic, there is also the IRC channel #restic
on irc.freenode.net.
**Important**: If you discover something that you believe to be a possible critical
security problem, please do *not* open a GitHub issue but send an email directly to
alexander@bumpern.de. If possible, please encrypt your email using the following PGP key
([0x91A6868BD3F7A907](https://pgp.mit.edu/pks/lookup?op=get&search=0xCF8F18F2844575973F79D4E191A6868BD3F7A907)):
```
pub 4096R/91A6868BD3F7A907 2014-11-01
Key fingerprint = CF8F 18F2 8445 7597 3F79 D4E1 91A6 868B D3F7 A907
uid Alexander Neumann <alexander@bumpern.de>
sub 4096R/D5FC2ACF4043FDF1 2014-11-01
```
License
=======
Restic is licensed under "BSD 2-Clause License". You can find the complete text
in the file `LICENSE`.

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|Documentation| |Build Status| |Build status| |Report Card|
Introduction
------------
restic is a backup program that is fast, efficient and secure.
For detailed usage and installation instructions check out the `documentation <https://restic.readthedocs.io/en/latest>`__.
Quick start
-----------
Once you've `installed <https://restic.readthedocs.io/en/latest/installation.html>`__ restic, start off with creating a repository for your backups::
$ restic init --repo /tmp/backup
enter password for new backend:
enter password again:
created restic backend 085b3c76b9 at /tmp/backup
Please note that knowledge of your password is required to access the repository.
Losing your password means that your data is irrecoverably lost.
and add some data::
$ restic -r /tmp/backup backup ~/work
enter password for repository:
scan [/home/user/work]
scanned 764 directories, 1816 files in 0:00
[0:29] 100.00% 54.732 MiB/s 1.582 GiB / 1.582 GiB 2580 / 2580 items 0 errors ETA 0:00
duration: 0:29, 54.47MiB/s
snapshot 40dc1520 saved
For more options check out the `usage guide <https://restic.readthedocs.io/en/latest/usage.html>`__.
Design Principles
-----------------
Restic is a program that does backups right and was designed with the
following principles in mind:
- **Easy:** Doing backups should be a frictionless process, otherwise
you might be tempted to skip it. Restic should be easy to configure
and use, so that, in the event of a data loss, you can just restore
it. Likewise, restoring data should not be complicated.
- **Fast**: Backing up your data with restic should only be limited by
your network or hard disk bandwidth so that you can backup your files
every day. Nobody does backups if it takes too much time. Restoring
backups should only transfer data that is needed for the files that
are to be restored, so that this process is also fast.
- **Verifiable**: Much more important than backup is restore, so restic
enables you to easily verify that all data can be restored.
- **Secure**: Restic uses cryptography to guarantee confidentiality and
integrity of your data. The location the backup data is stored is
assumed not to be a trusted environment (e.g. a shared space where
others like system administrators are able to access your backups).
Restic is built to secure your data against such attackers.
- **Efficient**: With the growth of data, additional snapshots should
only take the storage of the actual increment. Even more, duplicate
data should be de-duplicated before it is actually written to the
storage back end to save precious backup space.
News
----
You can follow the restic project on Twitter `@resticbackup <https://twitter.com/resticbackup>`__ or by subscribing to
the `development blog <https://restic.github.io/blog/>`__.
License
-------
Restic is licensed under "BSD 2-Clause License". You can find the
complete text in ``LICENSE``.
.. |Documentation| image:: https://readthedocs.org/projects/restic/badge/?version=latest
:target: https://restic.readthedocs.io/en/latest/?badge=latest
.. |Build Status| image:: https://travis-ci.org/restic/restic.svg?branch=master
:target: https://travis-ci.org/restic/restic
.. |Build status| image:: https://ci.appveyor.com/api/projects/status/nuy4lfbgfbytw92q/branch/master?svg=true
:target: https://ci.appveyor.com/project/fd0/restic/branch/master
.. |Report Card| image:: http://goreportcard.com/badge/github.com/restic/restic
:target: http://goreportcard.com/report/github.com/restic/restic

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This document gives a high-level overview of the design and repository layout
of the restic backup program.
Terminology
===========
This section introduces terminology used in this document.
*Repository*: All data produced during a backup is sent to and stored in a
repository in a structured form, for example in a file system hierarchy with
several subdirectories. A repository implementation must be able to fulfill a
number of operations, e.g. list the contents.
*Blob*: A Blob combines a number of data bytes with identifying information
like the SHA-256 hash of the data and its length.
*Pack*: A Pack combines one or more Blobs, e.g. in a single file.
*Snapshot*: A Snapshot stands for the state of a file or directory that has
been backed up at some point in time. The state here means the content and meta
data like the name and modification time for the file or the directory and its
contents.
*Storage ID*: A storage ID is the SHA-256 hash of the content stored in the
repository. This ID is required in order to load the file from the repository.
Repository Format
=================
All data is stored in a restic repository. A repository is able to store data
of several different types, which can later be requested based on an ID. This
so-called "storage ID" is the SHA-256 hash of the content of a file. All files
in a repository are only written once and never modified afterwards. This
allows accessing and even writing to the repository with multiple clients in
parallel. Only the delete operation removes data from the repository.
Repositories consist of several directories and a top-level file called
`config`. For all other files stored in the repository, the name for the file
is the lower case hexadecimal representation of the storage ID, which is the
SHA-256 hash of the file's contents. This allows for easy verification of files
for accidental modifications, like disk read errors, by simply running the
program `sha256sum` on the file and comparing its output to the file name. If
the prefix of a filename is unique amongst all the other files in the same
directory, the prefix may be used instead of the complete filename.
Apart from the files stored within the `keys` directory, all files are encrypted
with AES-256 in counter mode (CTR). The integrity of the encrypted data is
secured by a Poly1305-AES message authentication code (sometimes also referred
to as a "signature").
In the first 16 bytes of each encrypted file the initialisation vector (IV) is
stored. It is followed by the encrypted data and completed by the 16 byte
MAC. The format is: `IV || CIPHERTEXT || MAC`. The complete encryption
overhead is 32 bytes. For each file, a new random IV is selected.
The file `config` is encrypted this way and contains a JSON document like the
following:
```json
{
"version": 1,
"id": "5956a3f67a6230d4a92cefb29529f10196c7d92582ec305fd71ff6d331d6271b",
"chunker_polynomial": "25b468838dcb75"
}
```
After decryption, restic first checks that the version field contains a version
number that it understands, otherwise it aborts. At the moment, the version is
expected to be 1. The field `id` holds a unique ID which consists of 32
random bytes, encoded in hexadecimal. This uniquely identifies the repository,
regardless if it is accessed via SFTP or locally. The field
`chunker_polynomial` contains a parameter that is used for splitting large
files into smaller chunks (see below).
Filesystem-Based Repositories
-----------------------------
The `local` and `sftp` backends are implemented using files and directories
stored in a file system. The directory layout is the same for both backend
types.
The basic layout of a repository stored in a `local` or `sftp` backend is shown
here:
/tmp/restic-repo
├── config
├── data
│ ├── 21
│ │ └── 2159dd48f8a24f33c307b750592773f8b71ff8d11452132a7b2e2a6a01611be1
│ ├── 32
│ │ └── 32ea976bc30771cebad8285cd99120ac8786f9ffd42141d452458089985043a5
│ ├── 59
│ │ └── 59fe4bcde59bd6222eba87795e35a90d82cd2f138a27b6835032b7b58173a426
│ ├── 73
│ │ └── 73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c
│ [...]
├── index
│ ├── c38f5fb68307c6a3e3aa945d556e325dc38f5fb68307c6a3e3aa945d556e325d
│ └── ca171b1b7394d90d330b265d90f506f9984043b342525f019788f97e745c71fd
├── keys
│ └── b02de829beeb3c01a63e6b25cbd421a98fef144f03b9a02e46eff9e2ca3f0bd7
├── locks
├── snapshots
│ └── 22a5af1bdc6e616f8a29579458c49627e01b32210d09adb288d1ecda7c5711ec
└── tmp
A local repository can be initialized with the `restic init` command, e.g.:
```console
$ restic -r /tmp/restic-repo init
```
The local and sftp backends will also accept the repository layout described in
the following section, so that remote repositories mounted locally e.g. via
fuse can be accessed. The layout auto-detection can be overridden by specifying
the option `-o local.layout=default`, valid values are `default`, `cloud` and
`s3`. The option for the sftp backend is named `sftp.layout`.
Object-Storage-Based Repositories
---------------------------------
Repositories in a backend based on an object store (e.g. Amazon s3) have the
same basic layout, with the exception that all data pack files are directly
saved in the `data` path, without the sub-directories listed for the
filesystem-based backends as listed in the previous section. The layout looks
like this:
/config
/data
├── 2159dd48f8a24f33c307b750592773f8b71ff8d11452132a7b2e2a6a01611be1
├── 32ea976bc30771cebad8285cd99120ac8786f9ffd42141d452458089985043a5
├── 59fe4bcde59bd6222eba87795e35a90d82cd2f138a27b6835032b7b58173a426
├── 73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c
[...]
/index
├── c38f5fb68307c6a3e3aa945d556e325dc38f5fb68307c6a3e3aa945d556e325d
└── ca171b1b7394d90d330b265d90f506f9984043b342525f019788f97e745c71fd
/keys
└── b02de829beeb3c01a63e6b25cbd421a98fef144f03b9a02e46eff9e2ca3f0bd7
/locks
/snapshots
└── 22a5af1bdc6e616f8a29579458c49627e01b32210d09adb288d1ecda7c5711ec
Unfortunately during development the s3 backend uses slightly different paths
(directory names use singular instead of plural for `key`, `lock`, and
`snapshot` files), for s3 the repository layout looks like this:
/config
/data
├── 2159dd48f8a24f33c307b750592773f8b71ff8d11452132a7b2e2a6a01611be1
├── 32ea976bc30771cebad8285cd99120ac8786f9ffd42141d452458089985043a5
├── 59fe4bcde59bd6222eba87795e35a90d82cd2f138a27b6835032b7b58173a426
├── 73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c
[...]
/index
├── c38f5fb68307c6a3e3aa945d556e325dc38f5fb68307c6a3e3aa945d556e325d
└── ca171b1b7394d90d330b265d90f506f9984043b342525f019788f97e745c71fd
/key
└── b02de829beeb3c01a63e6b25cbd421a98fef144f03b9a02e46eff9e2ca3f0bd7
/lock
/snapshot
└── 22a5af1bdc6e616f8a29579458c49627e01b32210d09adb288d1ecda7c5711ec
The s3 backend understands and accepts both forms, new backends are always
created with the former layout for compatibility reasons.
Pack Format
-----------
All files in the repository except Key and Pack files just contain raw data,
stored as `IV || Ciphertext || MAC`. Pack files may contain one or more Blobs
of data.
A Pack's structure is as follows:
EncryptedBlob1 || ... || EncryptedBlobN || EncryptedHeader || Header_Length
At the end of the Pack file is a header, which describes the content. The
header is encrypted and authenticated. `Header_Length` is the length of the
encrypted header encoded as a four byte integer in little-endian encoding.
Placing the header at the end of a file allows writing the blobs in a
continuous stream as soon as they are read during the backup phase. This
reduces code complexity and avoids having to re-write a file once the pack is
complete and the content and length of the header is known.
All the blobs (`EncryptedBlob1`, `EncryptedBlobN` etc.) are authenticated and
encrypted independently. This enables repository reorganisation without having
to touch the encrypted Blobs. In addition it also allows efficient indexing,
for only the header needs to be read in order to find out which Blobs are
contained in the Pack. Since the header is authenticated, authenticity of the
header can be checked without having to read the complete Pack.
After decryption, a Pack's header consists of the following elements:
Type_Blob1 || Length(EncryptedBlob1) || Hash(Plaintext_Blob1) ||
[...]
Type_BlobN || Length(EncryptedBlobN) || Hash(Plaintext_Blobn) ||
This is enough to calculate the offsets for all the Blobs in the Pack. Length
is the length of a Blob as a four byte integer in little-endian format. The
type field is a one byte field and labels the content of a blob according to
the following table:
Type | Meaning
-----|---------
0 | data
1 | tree
All other types are invalid, more types may be added in the future.
For reconstructing the index or parsing a pack without an index, first the last
four bytes must be read in order to find the length of the header. Afterwards,
the header can be read and parsed, which yields all plaintext hashes, types,
offsets and lengths of all included blobs.
Indexing
--------
Index files contain information about Data and Tree Blobs and the Packs they
are contained in and store this information in the repository. When the local
cached index is not accessible any more, the index files can be downloaded and
used to reconstruct the index. The files are encrypted and authenticated like
Data and Tree Blobs, so the outer structure is `IV || Ciphertext || MAC` again.
The plaintext consists of a JSON document like the following:
```json
{
"supersedes": [
"ed54ae36197f4745ebc4b54d10e0f623eaaaedd03013eb7ae90df881b7781452"
],
"packs": [
{
"id": "73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c",
"blobs": [
{
"id": "3ec79977ef0cf5de7b08cd12b874cd0f62bbaf7f07f3497a5b1bbcc8cb39b1ce",
"type": "data",
"offset": 0,
"length": 25
},{
"id": "9ccb846e60d90d4eb915848add7aa7ea1e4bbabfc60e573db9f7bfb2789afbae",
"type": "tree",
"offset": 38,
"length": 100
},
{
"id": "d3dc577b4ffd38cc4b32122cabf8655a0223ed22edfd93b353dc0c3f2b0fdf66",
"type": "data",
"offset": 150,
"length": 123
}
]
}, [...]
]
}
```
This JSON document lists Packs and the blobs contained therein. In this
example, the Pack `73d04e61` contains two data Blobs and one Tree blob, the
plaintext hashes are listed afterwards.
The field `supersedes` lists the storage IDs of index files that have been
replaced with the current index file. This happens when index files are
repacked, for example when old snapshots are removed and Packs are recombined.
There may be an arbitrary number of index files, containing information on
non-disjoint sets of Packs. The number of packs described in a single file is
chosen so that the file size is kept below 8 MiB.
Keys, Encryption and MAC
------------------------
All data stored by restic in the repository is encrypted with AES-256 in
counter mode and authenticated using Poly1305-AES. For encrypting new data first
16 bytes are read from a cryptographically secure pseudorandom number generator
as a random nonce. This is used both as the IV for counter mode and the nonce
for Poly1305. This operation needs three keys: A 32 byte for AES-256 for
encryption, a 16 byte AES key and a 16 byte key for Poly1305. For details see
the original paper [The Poly1305-AES message-authentication
code](http://cr.yp.to/mac/poly1305-20050329.pdf) by Dan Bernstein.
The data is then encrypted with AES-256 and afterwards a message authentication
code (MAC) is computed over the ciphertext, everything is then stored as
IV || CIPHERTEXT || MAC.
The directory `keys` contains key files. These are simple JSON documents which
contain all data that is needed to derive the repository's master encryption and
message authentication keys from a user's password. The JSON document from the
repository can be pretty-printed for example by using the Python module `json`
(shortened to increase readability):
$ python -mjson.tool /tmp/restic-repo/keys/b02de82*
{
"hostname": "kasimir",
"username": "fd0"
"kdf": "scrypt",
"N": 65536,
"r": 8,
"p": 1,
"created": "2015-01-02T18:10:13.48307196+01:00",
"data": "tGwYeKoM0C4j4/9DFrVEmMGAldvEn/+iKC3te/QE/6ox/V4qz58FUOgMa0Bb1cIJ6asrypCx/Ti/pRXCPHLDkIJbNYd2ybC+fLhFIJVLCvkMS+trdywsUkglUbTbi+7+Ldsul5jpAj9vTZ25ajDc+4FKtWEcCWL5ICAOoTAxnPgT+Lh8ByGQBH6KbdWabqamLzTRWxePFoYuxa7yXgmj9A==",
"salt": "uW4fEI1+IOzj7ED9mVor+yTSJFd68DGlGOeLgJELYsTU5ikhG/83/+jGd4KKAaQdSrsfzrdOhAMftTSih5Ux6w==",
}
When the repository is opened by restic, the user is prompted for the
repository password. This is then used with `scrypt`, a key derivation function
(KDF), and the supplied parameters (`N`, `r`, `p` and `salt`) to derive 64 key
bytes. The first 32 bytes are used as the encryption key (for AES-256) and the
last 32 bytes are used as the message authentication key (for Poly1305-AES).
These last 32 bytes are divided into a 16 byte AES key `k` followed by 16 bytes
of secret key `r`. The key `r` is then masked for use with Poly1305 (see the
paper for details).
Those message authentication keys (`k` and `r`) are used to compute a MAC over
the bytes contained in the JSON field `data` (after removing the Base64
encoding and not including the last 32 byte). If the password is incorrect or
the key file has been tampered with, the computed MAC will not match the last
16 bytes of the data, and restic exits with an error. Otherwise, the data is
decrypted with the encryption key derived from `scrypt`. This yields a JSON
document which contains the master encryption and message authentication keys
for this repository (encoded in Base64). The command `restic cat masterkey` can
be used as follows to decrypt and pretty-print the master key:
```console
$ restic -r /tmp/restic-repo cat masterkey
{
"mac": {
"k": "evFWd9wWlndL9jc501268g==",
"r": "E9eEDnSJZgqwTOkDtOp+Dw=="
},
"encrypt": "UQCqa0lKZ94PygPxMRqkePTZnHRYh1k1pX2k2lM2v3Q=",
}
```
All data in the repository is encrypted and authenticated with these master keys.
For encryption, the AES-256 algorithm in Counter mode is used. For message
authentication, Poly1305-AES is used as described above.
A repository can have several different passwords, with a key file for each.
This way, the password can be changed without having to re-encrypt all data.
Snapshots
---------
A snapshot represents a directory with all files and sub-directories at a
given point in time. For each backup that is made, a new snapshot is created. A
snapshot is a JSON document that is stored in an encrypted file below the
directory `snapshots` in the repository. The filename is the storage ID. This
string is unique and used within restic to uniquely identify a snapshot.
The command `restic cat snapshot` can be used as follows to decrypt and
pretty-print the contents of a snapshot file:
```console
$ restic -r /tmp/restic-repo cat snapshot 251c2e58
enter password for repository:
{
"time": "2015-01-02T18:10:50.895208559+01:00",
"tree": "2da81727b6585232894cfbb8f8bdab8d1eccd3d8f7c92bc934d62e62e618ffdf",
"dir": "/tmp/testdata",
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"tags": [
"NL"
]
}
```
Here it can be seen that this snapshot represents the contents of the directory
`/tmp/testdata`. The most important field is `tree`. When the meta data (e.g.
the tags) of a snapshot change, the snapshot needs to be re-encrypted and saved.
This will change the storage ID, so in order to relate these seemingly
different snapshots, a field `original` is introduced which contains the ID of
the original snapshot, e.g. after adding the tag `DE` to the snapshot above it
becomes:
```console
$ restic -r /tmp/restic-repo cat snapshot 22a5af1b
enter password for repository:
{
"time": "2015-01-02T18:10:50.895208559+01:00",
"tree": "2da81727b6585232894cfbb8f8bdab8d1eccd3d8f7c92bc934d62e62e618ffdf",
"dir": "/tmp/testdata",
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"tags": [
"NL",
"DE"
],
"original": "251c2e5841355f743f9d4ffd3260bee765acee40a6229857e32b60446991b837"
}
```
Once introduced, the `original` field is not modified when the snapshot's meta
data is changed again.
All content within a restic repository is referenced according to its SHA-256
hash. Before saving, each file is split into variable sized Blobs of data. The
SHA-256 hashes of all Blobs are saved in an ordered list which then represents
the content of the file.
In order to relate these plaintext hashes to the actual location within a Pack
file , an index is used. If the index is not available, the header of all data
Blobs can be read.
Trees and Data
--------------
A snapshot references a tree by the SHA-256 hash of the JSON string
representation of its contents. Trees and data are saved in pack files in a
subdirectory of the directory `data`.
The command `restic cat blob` can be used to inspect the tree referenced above
(piping the output of the command to `jq .` so that the JSON is indented):
```console
$ restic -r /tmp/restic-repo cat blob b8138ab08a4722596ac89c917827358da4672eac68e3c03a8115b88dbf4bfb59 | jq .
enter password for repository:
{
"nodes": [
{
"name": "testdata",
"type": "dir",
"mode": 493,
"mtime": "2014-12-22T14:47:59.912418701+01:00",
"atime": "2014-12-06T17:49:21.748468803+01:00",
"ctime": "2014-12-22T14:47:59.912418701+01:00",
"uid": 1000,
"gid": 100,
"user": "fd0",
"inode": 409704562,
"content": null,
"subtree": "b26e315b0988ddcd1cee64c351d13a100fedbc9fdbb144a67d1b765ab280b4dc"
}
]
}
```
A tree contains a list of entries (in the field `nodes`) which contain meta
data like a name and timestamps. When the entry references a directory, the
field `subtree` contains the plain text ID of another tree object.
When the command `restic cat blob` is used, the plaintext ID is needed to print
a tree. The tree referenced above can be dumped as follows:
```console
$ restic -r /tmp/restic-repo cat blob 8b238c8811cc362693e91a857460c78d3acf7d9edb2f111048691976803cf16e
enter password for repository:
{
"nodes": [
{
"name": "testfile",
"type": "file",
"mode": 420,
"mtime": "2014-12-06T17:50:23.34513538+01:00",
"atime": "2014-12-06T17:50:23.338468713+01:00",
"ctime": "2014-12-06T17:50:23.34513538+01:00",
"uid": 1000,
"gid": 100,
"user": "fd0",
"inode": 416863351,
"size": 1234,
"links": 1,
"content": [
"50f77b3b4291e8411a027b9f9b9e64658181cc676ce6ba9958b95f268cb1109d"
]
},
[...]
]
}
```
This tree contains a file entry. This time, the `subtree` field is not present
and the `content` field contains a list with one plain text SHA-256 hash.
The command `restic cat blob` can also be used to extract and decrypt data
given a plaintext ID, e.g. for the data mentioned above:
```console
$ restic -r /tmp/restic-repo cat blob 50f77b3b4291e8411a027b9f9b9e64658181cc676ce6ba9958b95f268cb1109d | sha256sum
enter password for repository:
50f77b3b4291e8411a027b9f9b9e64658181cc676ce6ba9958b95f268cb1109d -
```
As can be seen from the output of the program `sha256sum`, the hash matches the
plaintext hash from the map included in the tree above, so the correct data has
been returned.
Locks
-----
The restic repository structure is designed in a way that allows parallel
access of multiple instance of restic and even parallel writes. However, there
are some functions that work more efficient or even require exclusive access of
the repository. In order to implement these functions, restic processes are
required to create a lock on the repository before doing anything.
Locks come in two types: Exclusive and non-exclusive locks. At most one
process can have an exclusive lock on the repository, and during that time
there must not be any other locks (exclusive and non-exclusive). There may be
multiple non-exclusive locks in parallel.
A lock is a file in the subdir `locks` whose filename is the storage ID of
the contents. It is encrypted and authenticated the same way as other files
in the repository and contains the following JSON structure:
```json
{
"time": "2015-06-27T12:18:51.759239612+02:00",
"exclusive": false,
"hostname": "kasimir",
"username": "fd0",
"pid": 13607,
"uid": 1000,
"gid": 100
}
```
The field `exclusive` defines the type of lock. When a new lock is to be
created, restic checks all locks in the repository. When a lock is found, it
is tested if the lock is stale, which is the case for locks with timestamps
older than 30 minutes. If the lock was created on the same machine, even for
younger locks it is tested whether the process is still alive by sending a
signal to it. If that fails, restic assumes that the process is dead and
considers the lock to be stale.
When a new lock is to be created and no other conflicting locks are
detected, restic creates a new lock, waits, and checks if other locks
appeared in the repository. Depending on the type of the other locks and the
lock to be created, restic either continues or fails.
Backups and Deduplication
=========================
For creating a backup, restic scans the source directory for all files,
sub-directories and other entries. The data from each file is split into
variable length Blobs cut at offsets defined by a sliding window of 64 byte.
The implementation uses Rabin Fingerprints for implementing this Content
Defined Chunking (CDC). An irreducible polynomial is selected at random and
saved in the file `config` when a repository is initialized, so that watermark
attacks are much harder.
Files smaller than 512 KiB are not split, Blobs are of 512 KiB to 8 MiB in
size. The implementation aims for 1 MiB Blob size on average.
For modified files, only modified Blobs have to be saved in a subsequent
backup. This even works if bytes are inserted or removed at arbitrary positions
within the file.
Threat Model
============
The design goals for restic include being able to securely store backups in a
location that is not completely trusted, e.g. a shared system where others can
potentially access the files or (in the case of the system administrator) even
modify or delete them.
General assumptions:
* The host system a backup is created on is trusted. This is the most basic
requirement, and essential for creating trustworthy backups.
The restic backup program guarantees the following:
* Accessing the unencrypted content of stored files and metadata should not
be possible without a password for the repository. Everything except the
metadata included for informational purposes in the key files is encrypted and
authenticated.
* Modifications (intentional or unintentional) can be detected automatically
on several layers:
1. For all accesses of data stored in the repository it is checked whether
the cryptographic hash of the contents matches the storage ID (the
file's name). This way, modifications (bad RAM, broken harddisk) can be
detected easily.
2. Before decrypting any data, the MAC on the encrypted data is
checked. If there has been a modification, the MAC check will
fail. This step happens even before the data is decrypted, so data that
has been tampered with is not decrypted at all.
However, the restic backup program is not designed to protect against attackers
deleting files at the storage location. There is nothing that can be done about
this. If this needs to be guaranteed, get a secure location without any access
from third parties. If you assume that attackers have write access to your
files at the storage location, attackers are able to figure out (e.g. based on
the timestamps of the stored files) which files belong to what snapshot. When
only these files are deleted, the particular snapshot vanished and all
snapshots depending on data that has been added in the snapshot cannot be
restored completely. Restic is not designed to detect this attack.

20
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# Minimal makefile for Sphinx documentation
#
# You can set these variables from the command line.
SPHINXOPTS =
SPHINXBUILD = sphinx-build
SPHINXPROJ = restic
SOURCEDIR = .
BUILDDIR = _build
# Put it first so that "make" without argument is like "make help".
help:
@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
.PHONY: help Makefile
# Catch-all target: route all unknown targets to Sphinx using the new
# "make mode" option. $(O) is meant as a shortcut for $(SPHINXOPTS).
%: Makefile
@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)

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nhanks for using restic. This document will give you an overview of the basic
functionality provided by restic.
# Installing restic
## from pre-compiled binary
You can download the latest pre-compiled binary from the [restic release page](https://github.com/restic/restic/releases/latest).
## Mac OS X
If you are using Mac OS X, you can install restic using the
[homebrew](http://brew.sh/) packet manager:
```console
$ brew tap restic/restic
$ brew install restic
```
## archlinux
On archlinux, there is a package called `restic-git` which can be installed from AUR, e.g. with `pacaur`:
```console
$ pacaur -S restic-git
```
# Building restic
restic is written in the Go programming language and you need at least Go version 1.7.
Building restic may also work with older versions of Go, but that's not supported.
See the [Getting started](https://golang.org/doc/install) guide of the Go project for
instructions how to install Go.
In order to build restic from source, execute the following steps:
```console
$ git clone https://github.com/restic/restic
[...]
$ cd restic
$ go run build.go
```
You can easily cross-compile restic for all supported platforms, just supply
the target OS and platform via the command-line options like this (for Windows
and FreeBSD respectively):
$ go run build.go --goos windows --goarch amd64
$ go run build.go --goos freebsd --goarch 386
The resulting binary is statically linked and does not require any libraries.
At the moment, the only tested compiler for restic is the official Go compiler.
Building restic with gccgo may work, but is not supported.
# Usage help
Usage help is available:
```console
$ ./restic --help
restic is a backup program which allows saving multiple revisions of files and
directories in an encrypted repository stored on different backends.
Usage:
restic [command]
Available Commands:
backup create a new backup of files and/or directories
cat print internal objects to stdout
check check the repository for errors
find find a file or directory
forget forget removes snapshots from the repository
init initialize a new repository
key manage keys (passwords)
list list items in the repository
ls list files in a snapshot
mount mount the repository
prune remove unneeded data from the repository
rebuild-index build a new index file
restore extract the data from a snapshot
snapshots list all snapshots
tag modifies tags on snapshots
unlock remove locks other processes created
version Print version information
Flags:
--json set output mode to JSON for commands that support it
--no-lock do not lock the repo, this allows some operations on read-only repos
-p, --password-file string read the repository password from a file
-q, --quiet do not output comprehensive progress report
-r, --repo string repository to backup to or restore from (default: $RESTIC_REPOSITORY)
Use "restic [command] --help" for more information about a command.
```
Similar to programs such as `git`, restic has a number of sub-commands. You can
see these commands in the listing above. Each sub-command may have own
command-line options, and there is a help option for each command which lists
them, e.g. for the `backup` command:
```console
$ ./restic backup --help
The "backup" command creates a new snapshot and saves the files and directories
given as the arguments.
Usage:
restic backup [flags] FILE/DIR [FILE/DIR] ...
Flags:
-e, --exclude pattern exclude a pattern (can be specified multiple times)
--exclude-file string read exclude patterns from a file
--files-from string read the files to backup from file (can be combined with file args)
-f, --force force re-reading the target files/directories. Overrides the "parent" flag
-x, --one-file-system Exclude other file systems
--parent string use this parent snapshot (default: last snapshot in the repo that has the same target files/directories)
--stdin read backup from stdin
--stdin-filename string file name to use when reading from stdin
--tag tag add a tag for the new snapshot (can be specified multiple times)
Global Flags:
--json set output mode to JSON for commands that support it
--no-lock do not lock the repo, this allows some operations on read-only repos
-p, --password-file string read the repository password from a file
-q, --quiet do not output comprehensive progress report
-r, --repo string repository to backup to or restore from (default: $RESTIC_REPOSITORY)
```
Subcommand that support showing progress information such as `backup`, `check` and `prune` will do so unless
the quiet flag `-q` or `--quiet` is set. When running from a non-interactive console progress reporting will
be limited to once every 10 seconds to not fill your logs.
Additionally on Unix systems if `restic` receives a SIGUSR signal the current progress will written to the
standard output so you can check up on the status at will.
# Initialize a repository
First, we need to create a "repository". This is the place where your backups
will be saved at.
In order to create a repository at `/tmp/backup`, run the following command and
enter the same password twice:
```console
$ restic init --repo /tmp/backup
enter password for new backend:
enter password again:
created restic backend 085b3c76b9 at /tmp/backup
Please note that knowledge of your password is required to access the repository.
Losing your password means that your data is irrecoverably lost.
```
Other backends like sftp and s3 are [described in a later section](#create-an-sftp-repository) of this document.
Remembering your password is important! If you lose it, you won't be able to
access data stored in the repository.
For automated backups, restic accepts the repository location in the
environment variable `RESTIC_REPOSITORY`. The password can be read from a file
(via the option `--password-file`) or the environment variable
`RESTIC_PASSWORD`.
## Password prompt on Windows
At the moment, restic only supports the default Windows console interaction.
If you use emulation environments like [MSYS2](https://msys2.github.io/) or
[Cygwin](https://www.cygwin.com/), which use terminals like `Mintty` or `rxvt`,
you may get a password error:
You can workaround this by using a special tool called `winpty` (look
[here](https://sourceforge.net/p/msys2/wiki/Porting/) and
[here](https://github.com/rprichard/winpty) for detail information). On MSYS2,
you can install `winpty` as follows:
```console
$ pacman -S winpty
$ winpty restic -r /tmp/backup init
```
# Create a snapshot
Now we're ready to backup some data. The contents of a directory at a specific
point in time is called a "snapshot" in restic. Run the following command and
enter the repository password you chose above again:
```console
$ restic -r /tmp/backup backup ~/work
enter password for repository:
scan [/home/user/work]
scanned 764 directories, 1816 files in 0:00
[0:29] 100.00% 54.732 MiB/s 1.582 GiB / 1.582 GiB 2580 / 2580 items 0 errors ETA 0:00
duration: 0:29, 54.47MiB/s
snapshot 40dc1520 saved
```
As you can see, restic created a backup of the directory and was pretty fast!
The specific snapshot just created is identified by a sequence of hexadecimal
characters, `40dc1520` in this case.
If you run the command again, restic will create another snapshot of your data,
but this time it's even faster. This is de-duplication at work!
```console
$ restic -r /tmp/backup backup ~/shared/work/web
enter password for repository:
using parent snapshot 40dc1520aa6a07b7b3ae561786770a01951245d2367241e71e9485f18ae8228c
scan [/home/user/work]
scanned 764 directories, 1816 files in 0:00
[0:00] 100.00% 0B/s 1.582 GiB / 1.582 GiB 2580 / 2580 items 0 errors ETA 0:00
duration: 0:00, 6572.38MiB/s
snapshot 79766175 saved
```
You can even backup individual files in the same repository.
```console
$ restic -r /tmp/backup backup ~/work.txt
scan [~/work.txt]
scanned 0 directories, 1 files in 0:00
[0:00] 100.00% 0B/s 220B / 220B 1 / 1 items 0 errors ETA 0:00
duration: 0:00, 0.03MiB/s
snapshot 31f7bd63 saved
```
In fact several hosts may use the same repository to backup directories and
files leading to a greater de-duplication.
Please be aware that when you backup different directories (or the directories
to be saved have a variable name component like a time/date), restic always
needs to read all files and only afterwards can compute which parts of the
files need to be saved. When you backup the same directory again (maybe with
new or changed files) restic will find the old snapshot in the repo and by
default only reads those files that are new or have been modified since the
last snapshot. This is decided based on the modify date of the file in the
file system.
You can exclude folders and files by specifying exclude-patterns.
Either specify them with multiple `--exclude`'s or one `--exclude-file`
```console
$ cat exclude
# exclude go-files
*.go
# exclude foo/x/y/z/bar foo/x/bar foo/bar
foo/**/bar
$ restic -r /tmp/backup backup ~/work --exclude=*.c --exclude-file=exclude
```
Patterns use [`filepath.Glob`](https://golang.org/pkg/path/filepath/#Glob) internally,
see [`filepath.Match`](https://golang.org/pkg/path/filepath/#Match) for syntax.
Additionally `**` excludes arbitrary subdirectories.
Environment-variables in exclude-files are expanded with [`os.ExpandEnv`](https://golang.org/pkg/os/#ExpandEnv).
By specifying the option `--one-file-system` you can instruct restic to only
backup files from the file systems the initially specified files or directories
reside on. For example, calling restic like this won't backup `/sys` or
`/dev` on a Linux system:
```console
$ restic -r /tmp/backup backup --one-file-system /
```
By using the `--files-from` option you can read the files you want to backup
from a file. This is especially useful if a lot of files have to be backed up
that are not in the same folder or are maybe pre-filtered by other software.
For example maybe you want to backup files that have a certain filename in them:
```console
$ find /tmp/somefiles | grep 'PATTERN' > /tmp/files_to_backup
```
You can then use restic to backup the filtered files:
```console
$ restic -r /tmp/backup backup --files-from /tmp/files_to_backup
```
Incidentally you can also combine `--files-from` with the normal files args:
```console
$ restic -r /tmp/backup backup --files-from /tmp/files_to_backup /tmp/some_additional_file
```
## Reading data from stdin
Sometimes it can be nice to directly save the output of a program, e.g.
`mysqldump` so that the SQL can later be restored. Restic supports this mode of
operation, just supply the option `--stdin` to the `backup` command like this:
```console
$ mysqldump [...] | restic -r /tmp/backup backup --stdin
```
This creates a new snapshot of the output of `mysqldump`. You can then use e.g.
the fuse mounting option (see below) to mount the repository and read the file.
By default, the file name `stdin` is used, a different name can be specified
with `--stdin-filename`, e.g. like this:
```console
$ mysqldump [...] | restic -r /tmp/backup backup --stdin --stdin-filename production.sql
```
## Tags
Snapshots can have one or more tags, short strings which add identifying
information. Just specify the tags for a snapshot with `--tag`:
```console
$ restic -r /tmp/backup backup --tag projectX ~/shared/work/web
[...]
```
The tags can later be used to keep (or forget) snapshots.
# List all snapshots
Now, you can list all the snapshots stored in the repository:
```console
$ restic -r /tmp/backup snapshots
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
40dc1520 2015-05-08 21:38:30 kasimir /home/user/work
79766175 2015-05-08 21:40:19 kasimir /home/user/work
bdbd3439 2015-05-08 21:45:17 luigi /home/art
590c8fc8 2015-05-08 21:47:38 kazik /srv
9f0bc19e 2015-05-08 21:46:11 luigi /srv
```
You can filter the listing by directory path:
```console
$ restic -r /tmp/backup snapshots --path="/srv"
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
590c8fc8 2015-05-08 21:47:38 kazik /srv
9f0bc19e 2015-05-08 21:46:11 luigi /srv
```
Or filter by host:
```console
$ restic -r /tmp/backup snapshots --host luigi
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
bdbd3439 2015-05-08 21:45:17 luigi /home/art
9f0bc19e 2015-05-08 21:46:11 luigi /srv
```
Combining filters is also possible.
# Restore a snapshot
Restoring a snapshot is as easy as it sounds, just use the following command to
restore the contents of the latest snapshot to `/tmp/restore-work`:
```console
$ restic -r /tmp/backup restore 79766175 --target ~/tmp/restore-work
enter password for repository:
restoring <Snapshot of [/home/user/work] at 2015-05-08 21:40:19.884408621 +0200 CEST> to /tmp/restore-work
```
Use the word `latest` to restore the last backup. You can also combine `latest`
with the `--host` and `--path` filters to choose the last backup for a specific
host, path or both.
```console
$ restic -r /tmp/backup restore latest --target ~/tmp/restore-work --path "/home/art" --host luigi
enter password for repository:
restoring <Snapshot of [/home/art] at 2015-05-08 21:45:17.884408621 +0200 CEST> to /tmp/restore-work
```
# Manage repository keys
The `key` command allows you to set multiple access keys or passwords per
repository. In fact, you can use the `list`, `add`, `remove` and `passwd`
sub-commands to manage these keys very precisely:
```console
$ restic -r /tmp/backup key list
enter password for repository:
ID User Host Created
----------------------------------------------------------------------
*eb78040b username kasimir 2015-08-12 13:29:57
$ restic -r /tmp/backup key add
enter password for repository:
enter password for new key:
enter password again:
saved new key as <Key of username@kasimir, created on 2015-08-12 13:35:05.316831933 +0200 CEST>
$ restic -r backup key list
enter password for repository:
ID User Host Created
----------------------------------------------------------------------
5c657874 username kasimir 2015-08-12 13:35:05
*eb78040b username kasimir 2015-08-12 13:29:57
```
# Manage tags
Managing tags on snapshots is done with the `tag` command. The existing set of
tags can be replaced completely, tags can be added to removed. The result is
directly visible in the `snapshots` command.
Let's say we want to tag snapshot `590c8fc8` with the tags `NL` and `CH` and
remove all other tags that may be present, the following command does that:
```console
$ restic -r /tmp/backup tag --set NL,CH 590c8fc8
Create exclusive lock for repository
Modified tags on 1 snapshots
```
Note the snapshot ID has changed, so between each change we need to look up
the new ID of the snapshot. But there is an even better way, the `tag` command
accepts `--tag` for a filter, so we can filter snapshots based on the tag we
just added.
So we can add and remove tags incrementally like this:
```console
$ restic -r /tmp/backup tag --tag NL --remove CH
Create exclusive lock for repository
Modified tags on 1 snapshots
$ restic -r /tmp/backup tag --tag NL --add UK
Create exclusive lock for repository
Modified tags on 1 snapshots
$ restic -r /tmp/backup tag --tag NL --remove NL
Create exclusive lock for repository
Modified tags on 1 snapshots
$ restic -r /tmp/backup tag --tag NL --add SOMETHING
No snapshots were modified
```
# Check integrity and consistency
Imagine your repository is saved on a server that has a faulty hard drive, or
even worse, attackers get privileged access and modify your backup with the
intention to make you restore malicious data:
```console
$ sudo echo "boom" >> backup/index/d795ffa99a8ab8f8e42cec1f814df4e48b8f49129360fb57613df93739faee97
```
In order to detect these things, it is a good idea to regularly use the `check`
command to test whether everything is alright, your precious backup data is
consistent and the integrity is unharmed:
```console
$ restic -r /tmp/backup check
Load indexes
ciphertext verification failed
```
Trying to restore a snapshot which has been modified as shown above will yield
the same error:
```console
$ restic -r /tmp/backup restore 79766175 --target ~/tmp/restore-work
Load indexes
ciphertext verification failed
```
# Mount a repository
Browsing your backup as a regular file system is also very easy. First, create
a mount point such as `/mnt/restic` and then use the following command to serve
the repository with FUSE:
```console
$ mkdir /mnt/restic
$ restic -r /tmp/backup mount /mnt/restic
enter password for repository:
Now serving /tmp/backup at /tmp/restic
Don't forget to umount after quitting!
```
Mounting repositories via FUSE is not possible on Windows and OpenBSD.
Restic supports storage and preservation of hard links. However, since hard links
exist in the scope of a filesystem by definition, restoring hard links from a fuse
mount should be done by a program that preserves hard links. A program that does so
is rsync, used with the option --hard-links.
# Create an SFTP repository
In order to backup data via SFTP, you must first set up a server with SSH and
let it know your public key. Passwordless login is really important since
restic fails to connect to the repository if the server prompts for
credentials.
Once the server is configured, the setup of the SFTP repository can simply be
achieved by changing the URL scheme in the `init` command:
```console
$ restic -r sftp:user@host:/tmp/backup init
enter password for new backend:
enter password again:
created restic backend f1c6108821 at sftp:user@host:/tmp/backup
Please note that knowledge of your password is required to access the repository.
Losing your password means that your data is irrecoverably lost.
```
You can also specify a relative (read: no slash (`/`) character at the
beginning) directory, in this case the dir is relative to the remote user's
home directory.
The backend config string does not allow specifying a port. If you need to
contact an sftp server on a different port, you can create an entry in the
`ssh` file, usually located in your user's home directory at `~/.ssh/config` or
in `/etc/ssh/ssh_config`:
```
Host foo
User bar
Port 2222
```
Then use the specified host name `foo` normally (you don't need to specify the
user name in this case):
```
$ restic -r sftp:foo:/tmp/backup init
```
You can also add an entry with a special host name which does not exist, just
for use with restic, and use the `Hostname` option to set the real host name:
```
Host restic-backup-host
Hostname foo
User bar
Port 2222
```
Then use it in the backend specification:
```
$ restic -r sftp:restic-backup-host:/tmp/backup init
```
Last, if you'd like to use an entirely different program to create the SFTP
connection, you can specify the command to be run with the option
`-o sftp.command="foobar"`.
# Create a REST server repository
In order to backup data to the remote server via HTTP or HTTPS protocol,
you must first set up a remote [REST server](https://github.com/restic/rest-server)
instance. Once the server is configured, accessing it is achieved by changing the
URL scheme like this:
```console
$ restic -r rest:http://host:8000/
```
Depending on your REST server setup, you can use HTTPS protocol, password
protection, or multiple repositories. Or any combination of those features, as
you see fit. TCP/IP port is also configurable. Here are some more examples:
```console
$ restic -r rest:https://host:8000/
$ restic -r rest:https://user:pass@host:8000/
$ restic -r rest:https://user:pass@host:8000/my_backup_repo/
```
If you use TLS, make sure your certificates are signed, 'cause restic client
will refuse to communicate otherwise. It's easy to obtain such certificates
today, thanks to free certificate authorities like [Let’s
Encrypt](https://letsencrypt.org/).
REST server uses exactly the same directory structure as local backend, so you
should be able to access it both locally and via HTTP, even simultaneously.
# Create an Amazon S3 repository
Restic can backup data to any Amazon S3 bucket. However, in this case, changing the URL scheme is not enough since Amazon uses special security credentials to sign HTTP requests. By consequence, you must first setup the following environment variables with the credentials you obtained while creating the bucket.
```console
$ export AWS_ACCESS_KEY_ID=<MY_ACCESS_KEY>
$ export AWS_SECRET_ACCESS_KEY=<MY_SECRET_ACCESS_KEY>
```
You can then easily initialize a repository that uses your Amazon S3 as a backend, if the bucket does not exist yet it will be created in the default location:
```console
$ restic -r s3:s3.amazonaws.com/bucket_name init
enter password for new backend:
enter password again:
created restic backend eefee03bbd at s3:s3.amazonaws.com/bucket_name
Please note that knowledge of your password is required to access the repository.
Losing your password means that your data is irrecoverably lost.
```
It is not possible at the moment to have restic create a new bucket in a different location, so you need to create it using a different program. Afterwards, the S3 server (`s3.amazonaws.com`) will redirect restic to the correct endpoint.
For an S3-compatible server that is not Amazon (like Minio, see below), or is
only available via HTTP, you can specify the URL to the server like this:
`s3:http://server:port/bucket_name`.
## Create a Minio Server repository
[Minio](https://www.minio.io) is an Open Source Object Storage, written in Go and compatible with AWS S3 API.
### Pre-Requisites
* Download and Install [Minio Server](https://minio.io/downloads/#minio-server).
* You can also refer to [https://docs.minio.io](https://docs.minio.io) for step by step guidance on installation and getting started on Minio Client and Minio Server.
You must first setup the following environment variables with the credentials of your running Minio Server.
```console
$ export AWS_ACCESS_KEY_ID=<YOUR-MINIO-ACCESS-KEY-ID>
$ export AWS_SECRET_ACCESS_KEY= <YOUR-MINIO-SECRET-ACCESS-KEY>
```
Now you can easily initialize restic to use Minio server as backend with this command.
```console
$ ./restic -r s3:http://localhost:9000/restic init
enter password for new backend:
enter password again:
created restic backend 6ad29560f5 at s3:http://localhost:9000/restic1
Please note that knowledge of your password is required to access
the repository. Losing your password means that your data is irrecoverably lost.
```
# Removing old snapshots
All backup space is finite, so restic allows removing old snapshots. This can
be done either manually (by specifying a snapshot ID to remove) or by using a
policy that describes which snapshots to forget. For all remove operations, two
commands need to be called in sequence: `forget` to remove a snapshot and
`prune` to actually remove the data that was referenced by the snapshot from
the repository. This can be automated with the `--prune` option of the `forget`
command, which runs `prune` automatically if snapshots have been removed.
## Remove a single snapshot
The command `snapshots` can be used to list all snapshots in a repository like this:
```console
$ restic -r /tmp/backup snapshots
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
40dc1520 2015-05-08 21:38:30 kasimir /home/user/work
79766175 2015-05-08 21:40:19 kasimir /home/user/work
bdbd3439 2015-05-08 21:45:17 luigi /home/art
590c8fc8 2015-05-08 21:47:38 kazik /srv
9f0bc19e 2015-05-08 21:46:11 luigi /srv
```
In order to remove the snapshot of `/home/art`, use the `forget` command and
specify the snapshot ID on the command line:
```console
$ restic -r /tmp/backup forget bdbd3439
enter password for repository:
removed snapshot d3f01f63
```
Afterwards this snapshot is removed:
```console
$ restic -r /tmp/backup snapshots
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
40dc1520 2015-05-08 21:38:30 kasimir /home/user/work
79766175 2015-05-08 21:40:19 kasimir /home/user/work
590c8fc8 2015-05-08 21:47:38 kazik /srv
9f0bc19e 2015-05-08 21:46:11 luigi /srv
```
But the data that was referenced by files in this snapshot is still stored in
the repository. To cleanup unreferenced data, the `prune` command must be run:
```console
$ restic -r /tmp/backup prune
enter password for repository:
counting files in repo
building new index for repo
[0:00] 100.00% 22 / 22 files
repository contains 22 packs (8512 blobs) with 100.092 MiB bytes
processed 8512 blobs: 0 duplicate blobs, 0B duplicate
load all snapshots
find data that is still in use for 1 snapshots
[0:00] 100.00% 1 / 1 snapshots
found 8433 of 8512 data blobs still in use
will rewrite 3 packs
creating new index
[0:00] 86.36% 19 / 22 files
saved new index as 544a5084
done
```
Afterwards the repository is smaller.
You can automate this two-step process by using the `--prune` switch to
`forget`:
```console
$ restic forget --keep-last 1 --prune
snapshots for host mopped, directories /home/user/work:
keep 1 snapshots:
ID Date Host Tags Directory
----------------------------------------------------------------------
4bba301e 2017-02-21 10:49:18 mopped /home/user/work
remove 1 snapshots:
ID Date Host Tags Directory
----------------------------------------------------------------------
8c02b94b 2017-02-21 10:48:33 mopped /home/user/work
1 snapshots have been removed, running prune
counting files in repo
building new index for repo
[0:00] 100.00% 37 / 37 packs
repository contains 37 packs (5521 blobs) with 151.012 MiB bytes
processed 5521 blobs: 0 duplicate blobs, 0B duplicate
load all snapshots
find data that is still in use for 1 snapshots
[0:00] 100.00% 1 / 1 snapshots
found 5323 of 5521 data blobs still in use, removing 198 blobs
will delete 0 packs and rewrite 27 packs, this frees 22.106 MiB
creating new index
[0:00] 100.00% 30 / 30 packs
saved new index as b49f3e68
done
```
## Removing snapshots according to a policy
Removing snapshots manually is tedious and error-prone, therefore restic allows
specifying which snapshots should be removed automatically according to a
policy. You can specify how many hourly, daily, weekly, monthly and yearly
snapshots to keep, any other snapshots are removed. The most important
command-line parameter here is `--dry-run` which instructs restic to not remove
anything but print which snapshots would be removed.
When `forget` is run with a policy, restic loads the list of all snapshots,
then groups these by host name and list of directories. The policy is then
applied to each group of snapshots separately. This is a safety feature.
The `forget` command accepts the following parameters:
* `--keep-last n` never delete the `n` last (most recent) snapshots
* `--keep-hourly n` for the last `n` hours in which a snapshot was made, keep
only the last snapshot for each hour.
* `--keep-daily n` for the last `n` days which have one or more snapshots, only
keep the last one for that day.
* `--keep-weekly n` for the last `n` weeks which have one or more snapshots, only
keep the last one for that week.
* `--keep-monthly n` for the last `n` months which have one or more snapshots, only
keep the last one for that month.
* `--keep-yearly n` for the last `n` years which have one or more snapshots, only
keep the last one for that year.
* `--keep-tag` keep all snapshots which have all tags specified by this option
(can be specified multiple times).
Additionally, you can restrict removing snapshots to those which have a
particular hostname with the `--hostname` parameter, or tags with the `--tag`
option. When multiple tags are specified, only the snapshots which have all the
tags are considered.
All the `--keep-*` options above only count hours/days/weeks/months/years which
have a snapshot, so those without a snapshot are ignored.
Let's explain this with an example: Suppose you have only made a backup on each
Sunday for 12 weeks. Then `forget --keep-daily 4` will keep the last four snapshots
for the last four Sundays, but remove the rest. Only counting the days which
have a backup and ignore the ones without is a safety feature: it prevents
restic from removing many snapshots when no new ones are created. If it was
implemented otherwise, running `forget --keep-daily 4` on a Friday would remove
all snapshots!
# Debugging restic
The program can be built with debug support like this:
```console
$ go run build.go -tags debug
```
Afterwards, extensive debug messages are written to the file in environment
variable `DEBUG_LOG`, e.g.:
```console
$ DEBUG_LOG=/tmp/restic-debug.log restic backup ~/work
```
If you suspect that there is a bug, you can have a look at the debug log.
Please be aware that the debug log might contain sensitive information such as
file and directory names.
The debug log will always contain all log messages restic generates. You can
also instruct restic to print some or all debug messages to stderr. These can
also be limited to e.g. a list of source files or a list of patterns for
function names. The patterns are globbing patterns (see the documentation for
[`path.Glob`](https://golang.org/pkg/path/#Glob)), multiple patterns are
separated by commas. Patterns are case sensitive.
Printing all log messages to the console can be achieved by setting the file
filter to `*`:
```console
$ DEBUG_FILES=* restic check
```
If you want restic to just print all debug log messages from the files
`main.go` and `lock.go`, set the environment variable `DEBUG_FILES` like this:
```console
$ DEBUG_FILES=main.go,lock.go restic check
```
The following command line instructs restic to only print debug statements
originating in functions that match the pattern `*unlock*` (case sensitive):
```console
$ DEBUG_FUNCS=*unlock* restic check
```
# Under the hood: Browse repository objects
Internally, a repository stores data of several different types described in the [design documentation](https://github.com/restic/restic/blob/master/doc/Design.md). You can `list` objects such as blobs, packs, index, snapshots, keys or locks with the following command:
```console
$ restic -r /tmp/backup list snapshots
d369ccc7d126594950bf74f0a348d5d98d9e99f3215082eb69bf02dc9b3e464c
```
The `find` command searches for a given
[pattern](http://golang.org/pkg/path/filepath/#Match) in the repository.
```console
$ restic -r backup find test.txt
debug log file restic.log
debug enabled
enter password for repository:
found 1 matching entries in snapshot 196bc5760c909a7681647949e80e5448e276521489558525680acf1bd428af36
-rw-r--r-- 501 20 5 2015-08-26 14:09:57 +0200 CEST path/to/test.txt
```
The `cat` command allows you to display the JSON representation of the objects
or its raw content.
```console
$ restic -r /tmp/backup cat snapshot d369ccc7d126594950bf74f0a348d5d98d9e99f3215082eb69bf02dc9b3e464c
enter password for repository:
{
"time": "2015-08-12T12:52:44.091448856+02:00",
"tree": "05cec17e8d3349f402576d02576a2971fc0d9f9776ce2f441c7010849c4ff5af",
"paths": [
"/home/user/work"
],
"hostname": "kasimir",
"username": "username",
"uid": 501,
"gid": 20
}
```
# Scripting restic
Restic supports the output of some commands in JSON format, the JSON data can
then be processed by other programs (e.g. [`jq`](https://stedolan.github.io/jq/)).
The following example lists all snapshots as JSON and uses `jq` to pretty-print
the result:
```console
$ restic -r /tmp/backup snapshots --json | jq .
[
{
"time": "2017-03-11T09:57:43.26630619+01:00",
"tree": "bf25241679533df554fc0fd0ae6dbb9dcf1859a13f2bc9dd4543c354eff6c464",
"paths": [
"/home/work/doc"
],
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"id": "bbeed6d28159aa384d1ccc6fa0b540644b1b9599b162d2972acda86b1b80f89e"
},
{
"time": "2017-03-11T09:58:57.541446938+01:00",
"tree": "7f8c95d3420baaac28dc51609796ae0e0ecfb4862b609a9f38ffaf7ae2d758da",
"paths": [
"/home/user/shared"
],
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"id": "b157d91c16f0ba56801ece3a708dfc53791fe2a97e827090d6ed9a69a6ebdca0"
}
]
```
# Temporary files
During some operations (e.g. `backup` and `prune`) restic uses temporary files
to store data. These files will, by default, be saved to the system's temporary
directory, on Linux this is usually located in `/tmp/`. The environment
variable `TMPDIR` can be used to specify a different directory, e.g. to use the
directory `/var/tmp/restic-tmp` instead of the default, set the environment
variable like this:
```console
$ export TMPDIR=/var/tmp/restic-tmp
$ restic -r /tmp/backup backup ~/work
```

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REST Backend
============
Restic can interact with HTTP Backend that respects the following REST API. The
following values are valid for `{type}`: `data`, `keys`, `locks`, `snapshots`,
`index`, `config`. `{path}` is a path to the repository, so that multiple
different repositories can be accessed. The default path is `/`.
## POST {path}?create=true
This request is used to initially create a new repository. The server responds
with "200 OK" if the repository structure was created successfully or already
exists, otherwise an error is returned.
## DELETE {path}
Deletes the repository on the server side. The server responds with "200 OK" if
the repository was successfully removed. If this function is not implemented
the server returns "501 Not Implemented", if this it is denied by the server it
returns "403 Forbidden".
## HEAD {path}/config
Returns "200 OK" if the repository has a configuration,
an HTTP error otherwise.
## GET {path}/config
Returns the content of the configuration file if the repository has a configuration,
an HTTP error otherwise.
Response format: binary/octet-stream
## POST {path}/config
Returns "200 OK" if the configuration of the request body has been saved,
an HTTP error otherwise.
## GET {path}/{type}/
Returns a JSON array containing the names of all the blobs stored for a given type.
Response format: JSON
## HEAD {path}/{type}/{name}
Returns "200 OK" if the blob with the given name and type is stored in the repository,
"404 not found" otherwise. If the blob exists, the HTTP header `Content-Length`
is set to the file size.
## GET {path}/{type}/{name}
Returns the content of the blob with the given name and type if it is stored in the repository,
"404 not found" otherwise.
If the request specifies a partial read with a Range header field,
then the status code of the response is 206 instead of 200
and the response only contains the specified range.
Response format: binary/octet-stream
## POST {path}/{type}/{name}
Saves the content of the request body as a blob with the given name and type,
an HTTP error otherwise.
Request format: binary/octet-stream
## DELETE {path}/{type}/{name}
Returns "200 OK" if the blob with the given name and type has been deleted from the repository,
an HTTP error otherwise.

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@import url('theme.css');
.wy-side-nav-search {
background-color: #0000b4;
}
.logo {
height: 50% !important;
width: 50% !important;
}

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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#
# restic documentation build configuration file, created by
# sphinx-quickstart on Fri Apr 14 22:44:43 2017.
#
# This file is execfile()d with the current directory set to its
# containing dir.
#
# Note that not all possible configuration values are present in this
# autogenerated file.
#
# All configuration values have a default; values that are commented out
# serve to show the default.
import os
# -- General configuration ------------------------------------------------
# Add any Sphinx extension module names here, as strings. They can be
# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
# ones.
extensions = []
# Add any paths that contain templates here, relative to this directory.
templates_path = ['_templates']
# The suffix(es) of source filenames.
# You can specify multiple suffix as a list of string:
#
# source_suffix = ['.rst', '.md']
source_suffix = '.rst'
# The master toctree document.
master_doc = 'index'
# General information about the project.
project = 'restic'
copyright = '2017, restic authors'
author = 'fd0'
# The version info for the project you're documenting, acts as replacement for
# |version| and |release|, also used in various other places throughout the
# built documents.
#
# The short X.Y version.
# read version from ../VERSION
version = open('../VERSION').readlines()[0]
# The full version, including alpha/beta/rc tags.
release = version
# The language for content autogenerated by Sphinx. Refer to documentation
# for a list of supported languages.
#
# This is also used if you do content translation via gettext catalogs.
# Usually you set "language" from the command line for these cases.
language = None
# List of patterns, relative to source directory, that match files and
# directories to ignore when looking for source files.
# This patterns also effect to html_static_path and html_extra_path
exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
# The name of the Pygments (syntax highlighting) style to use.
pygments_style = 'sphinx'
# If true, `todo` and `todoList` produce output, else they produce nothing.
todo_include_todos = False
# -- Options for HTML output ----------------------------------------------
# The theme to use for HTML and HTML Help pages. See the documentation for
# a list of builtin themes.
#
if os.environ.get('READTHEDOCS') == 'True':
html_context = {
'css_files': [
'https://media.readthedocs.org/css/sphinx_rtd_theme.css',
'https://media.readthedocs.org/css/readthedocs-doc-embed.css',
'_static/css/restic.css',
]
}
else:
# we're not built by rtd => add rtd-theme
import sphinx_rtd_theme
html_theme = 'sphinx_rtd_theme'
html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
html_style = 'css/restic.css'
html_logo = 'logo/logo.png'
html_favicon = '_static/favicon.ico'
html_show_version = False
# Add any paths that contain custom static files (such as style sheets) here,
# relative to this directory. They are copied after the builtin static files,
# so a file named "default.css" will overwrite the builtin "default.css".
html_static_path = ['_static']
# -- Options for HTMLHelp output ------------------------------------------
# Output file base name for HTML help builder.
htmlhelp_basename = 'resticdoc'

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Development
===========
Contribute
----------
Contributions are welcome! Please **open an issue first** (or add a
comment to an existing issue) if you plan to work on any code or add a
new feature. This way, duplicate work is prevented and we can discuss
your ideas and design first.
More information and a description of the development environment can be
found in `CONTRIBUTING.md <CONTRIBUTING.md>`__.
A document describing the design of restic and the data structures stored on the
back end is contained in `Design <https://restic.readthedocs.io/en/latest/design.html>`__.
If you'd like to start contributing to restic, but don't know exactly
what do to, have a look at this great article by Dave Cheney:
`Suggestions for contributing to an Open Source
project <http://dave.cheney.net/2016/03/12/suggestions-for-contributing-to-an-open-source-project>`__
A few issues have been tagged with the label ``help wanted``, you can
start looking at those:
https://github.com/restic/restic/labels/help%20wanted
Security
--------
**Important**: If you discover something that you believe to be a
possible critical security problem, please do *not* open a GitHub issue
but send an email directly to alexander@bumpern.de. If possible, please
encrypt your email using the following PGP key
(`0x91A6868BD3F7A907 <https://pgp.mit.edu/pks/lookup?op=get&search=0xCF8F18F2844575973F79D4E191A6868BD3F7A907>`__):
::
pub 4096R/91A6868BD3F7A907 2014-11-01
Key fingerprint = CF8F 18F2 8445 7597 3F79 D4E1 91A6 868B D3F7 A907
uid Alexander Neumann <alexander@bumpern.de>
sub 4096R/D5FC2ACF4043FDF1 2014-11-01
Compatibility
-------------
Backward compatibility for backups is important so that our users are
always able to restore saved data. Therefore restic follows `Semantic
Versioning <http://semver.org>`__ to clearly define which versions are
compatible. The repository and data structures contained therein are
considered the "Public API" in the sense of Semantic Versioning. This
goes for all released versions of restic, this may not be the case for
the master branch.
We guarantee backward compatibility of all repositories within one major
version; as long as we do not increment the major version, data can be
read and restored. We strive to be fully backward compatible to all
prior versions.
Building documentation
----------------------
The restic documentation is built with `Sphinx <http://sphinx-doc.org>`__,
therefore building it locally requires a recent Python version and requirements listed in ``doc/requirements.txt``.
This example will guide you through the process using `virtualenv <https://virtualenv.pypa.io>`__:
::
$ virtualenv venv # create virtual python environment
$ source venv/bin/activate # activate the virtual environment
$ cd doc
$ pip install -r requirements.txt # install dependencies
$ make html # build html documentation
$ # open _build/html/index.html with your favorite browser

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@ -3,10 +3,15 @@ FAQ
This is the list of Frequently Asked Questions for restic.
`restic check` reports packs that aren't referenced in any index, is my repository broken?
------------------------------------------------------------------------------------------
``restic check`` reports packs that aren't referenced in any index, is my repository broken?
--------------------------------------------------------------------------------------------
When `restic check` reports that there are pack files in the repository that are not referenced in any index, that's (in contrast to what restic reports at the moment) not a source for concern. The output looks like this:
When ``restic check`` reports that there are pack files in the
repository that are not referenced in any index, that's (in contrast to
what restic reports at the moment) not a source for concern. The output
looks like this:
::
$ restic check
Create exclusive lock for repository
@ -17,4 +22,7 @@ When `restic check` reports that there are pack files in the repository that are
Check snapshots, trees and blobs
Fatal: repository contains errors
The message means that there is more data stored in the repo than strictly necessary. With high probability this is duplicate data. In order to clean it up, the command `restic prune` can be used. The cause of this bug is not yet known.
The message means that there is more data stored in the repo than
strictly necessary. With high probability this is duplicate data. In
order to clean it up, the command ``restic prune`` can be used. The
cause of this bug is not yet known.

119
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Welcome to restic
=================
![restic logo](logo/logo.svg)
restic is a backup program that is fast, efficient and secure. On the left you
can find an overview of the documentation. The project's homepage is
<https://restic.github.io>, the source code repository can be found on GitHub
at the URL <https://github.com/restic/restic>.
Building and viewing the documentation
--------------------------------------
The documentation you're currently viewing may not match the version of restic
you have installed. If you cloned the repository manually, you can find the
right documentation in the directory `doc/`. If you're viewing this online at
<https://restic.readthedocs.io>, there is a small menu at the bottom left of
this page, where you can select the version.
The restic documentation is built with [MkDocs](http://www.mkdocs.org). After
installing it, you can edit and view the documentation locally by running:
```console
$ mkdocs serve
INFO - Building documentation...
INFO - Cleaning site directory
[I 160221 12:33:57 server:271] Serving on http://127.0.0.1:8000
```
Afterwards visit the URL with a browser.
Design Principles
-----------------
Restic is a program that does backups right and was designed with the following
principles in mind:
* **Easy:** Doing backups should be a frictionless process, otherwise you might be
tempted to skip it. Restic should be easy to configure and use, so that, in
the event of a data loss, you can just restore it. Likewise,
restoring data should not be complicated.
* **Fast**: Backing up your data with restic should only be limited by your
network or hard disk bandwidth so that you can backup your files every day.
Nobody does backups if it takes too much time. Restoring backups should only
transfer data that is needed for the files that are to be restored, so that
this process is also fast.
* **Verifiable**: Much more important than backup is restore, so restic enables
you to easily verify that all data can be restored.
* **Secure**: Restic uses cryptography to guarantee confidentiality and integrity
of your data. The location the backup data is stored is assumed not to be a
trusted environment (e.g. a shared space where others like system
administrators are able to access your backups). Restic is built to secure
your data against such attackers.
* **Efficient**: With the growth of data, additional snapshots should only take
the storage of the actual increment. Even more, duplicate data should be
de-duplicated before it is actually written to the storage back end to save
precious backup space.
Compatibility
-------------
Backward compatibility for backups is important so that our users are always
able to restore saved data. Therefore restic follows [Semantic
Versioning](http://semver.org) to clearly define which versions are compatible.
The repository and data structures contained therein are considered the "Public
API" in the sense of Semantic Versioning. This goes for all released versions
of restic, this may not be the case for the master branch.
We guarantee backward compatibility of all repositories within one major version;
as long as we do not increment the major version, data can be read and restored.
We strive to be fully backward compatible to all prior versions.
Contribute and Documentation
----------------------------
Contributions are welcome! More information can be found in the document
[`CONTRIBUTING.md`](https://github.com/restic/restic/blob/master/CONTRIBUTING.md).
Contact
-------
If you discover a bug, find something surprising or if you would like to
discuss or ask something, please [open a github
issue](https://github.com/restic/restic/issues/new). If you would like to chat
about restic, there is also the IRC channel #restic on irc.freenode.net.
**Important**: If you discover something that you believe to be a possible
critical security problem, please do *not* open a GitHub issue but send an
email directly to alexander@bumpern.de. If possible, please encrypt your email
using the following PGP key
([0x91A6868BD3F7A907](https://pgp.mit.edu/pks/lookup?op=get&search=0xCF8F18F2844575973F79D4E191A6868BD3F7A907)):
```
pub 4096R/91A6868BD3F7A907 2014-11-01
Key fingerprint = CF8F 18F2 8445 7597 3F79 D4E1 91A6 868B D3F7 A907
uid Alexander Neumann <alexander@bumpern.de>
sub 4096R/D5FC2ACF4043FDF1 2014-11-01
```
Talks
-----
The following talks will be or have been given about restic:
* 2016-01-31: Lightning Talk at the Go Devroom at FOSDEM 2016, Brussels, Belgium
* 2016-01-29: [restic - Backups mal richtig](https://media.ccc.de/v/c4.openchaos.2016.01.restic): Public lecture in German at [CCC Cologne e.V.](https://koeln.ccc.de) in Cologne, Germany
* 2015-08-23: [A Solution to the Backup Inconvenience](https://programm.froscon.de/2015/events/1515.html): Lecture at [FROSCON 2015](https://www.froscon.de) in Bonn, Germany
* 2015-02-01: [Lightning Talk at FOSDEM 2015](https://www.youtube.com/watch?v=oM-MfeflUZ8&t=11m40s): A short introduction (with slightly outdated command line)
* 2015-01-27: [Talk about restic at CCC Aachen](https://videoag.fsmpi.rwth-aachen.de/?view=player&lectureid=4442#content) (in German)
License
=======
Restic is licensed under "BSD 2-Clause License". You can find the complete text
in the file `LICENSE`.

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Restic Documentation
====================
.. toctree::
:maxdepth: 2
installation
manual
faq
development
references
talks
.. include:: ../README.rst

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Installation
============
Packages
--------
Mac OS X
~~~~~~~~~
If you are using Mac OS X, you can install restic using the
`homebrew <http://brew.sh/>`__ packet manager:
.. code:: console
$ brew tap restic/restic
$ brew install restic
archlinux
~~~~~~~~~
On archlinux, there is a package called ``restic-git`` which can be
installed from AUR, e.g. with ``pacaur``:
.. code:: console
$ pacaur -S restic-git
Pre-compiled Binary
-------------------
You can download the latest pre-compiled binary from the `restic release
page <https://github.com/restic/restic/releases/latest>`__.
From Source
-----------
restic is written in the Go programming language and you need at least
Go version 1.7. Building restic may also work with older versions of Go,
but that's not supported. See the `Getting
started <https://golang.org/doc/install>`__ guide of the Go project for
instructions how to install Go.
In order to build restic from source, execute the following steps:
.. code:: console
$ git clone https://github.com/restic/restic
[...]
$ cd restic
$ go run build.go
You can easily cross-compile restic for all supported platforms, just
supply the target OS and platform via the command-line options like this
(for Windows and FreeBSD respectively):
::
$ go run build.go --goos windows --goarch amd64
$ go run build.go --goos freebsd --goarch 386
The resulting binary is statically linked and does not require any
libraries.
At the moment, the only tested compiler for restic is the official Go
compiler. Building restic with gccgo may work, but is not supported.

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Manual
======
Usage help
----------
Usage help is available:
.. code:: console
$ ./restic --help
restic is a backup program which allows saving multiple revisions of files and
directories in an encrypted repository stored on different backends.
Usage:
restic [command]
Available Commands:
backup create a new backup of files and/or directories
cat print internal objects to stdout
check check the repository for errors
find find a file or directory
forget forget removes snapshots from the repository
init initialize a new repository
key manage keys (passwords)
list list items in the repository
ls list files in a snapshot
mount mount the repository
prune remove unneeded data from the repository
rebuild-index build a new index file
restore extract the data from a snapshot
snapshots list all snapshots
tag modifies tags on snapshots
unlock remove locks other processes created
version Print version information
Flags:
--json set output mode to JSON for commands that support it
--no-lock do not lock the repo, this allows some operations on read-only repos
-p, --password-file string read the repository password from a file
-q, --quiet do not output comprehensive progress report
-r, --repo string repository to backup to or restore from (default: $RESTIC_REPOSITORY)
Use "restic [command] --help" for more information about a command.
Similar to programs such as ``git``, restic has a number of
sub-commands. You can see these commands in the listing above. Each
sub-command may have own command-line options, and there is a help
option for each command which lists them, e.g. for the ``backup``
command:
.. code:: console
$ ./restic backup --help
The "backup" command creates a new snapshot and saves the files and directories
given as the arguments.
Usage:
restic backup [flags] FILE/DIR [FILE/DIR] ...
Flags:
-e, --exclude pattern exclude a pattern (can be specified multiple times)
--exclude-file string read exclude patterns from a file
--files-from string read the files to backup from file (can be combined with file args)
-f, --force force re-reading the target files/directories. Overrides the "parent" flag
-x, --one-file-system Exclude other file systems
--parent string use this parent snapshot (default: last snapshot in the repo that has the same target files/directories)
--stdin read backup from stdin
--stdin-filename string file name to use when reading from stdin
--tag tag add a tag for the new snapshot (can be specified multiple times)
Global Flags:
--json set output mode to JSON for commands that support it
--no-lock do not lock the repo, this allows some operations on read-only repos
-p, --password-file string read the repository password from a file
-q, --quiet do not output comprehensive progress report
-r, --repo string repository to backup to or restore from (default: $RESTIC_REPOSITORY)
Subcommand that support showing progress information such as ``backup``,
``check`` and ``prune`` will do so unless the quiet flag ``-q`` or
``--quiet`` is set. When running from a non-interactive console progress
reporting will be limited to once every 10 seconds to not fill your
logs.
Additionally on Unix systems if ``restic`` receives a SIGUSR signal the
current progress will written to the standard output so you can check up
on the status at will.
Initialize a repository
-----------------------
First, we need to create a "repository". This is the place where your
backups will be saved at.
Local
~~~~~
In order to create a repository at ``/tmp/backup``, run the following
command and enter the same password twice:
.. code:: console
$ restic init --repo /tmp/backup
enter password for new backend:
enter password again:
created restic backend 085b3c76b9 at /tmp/backup
Please note that knowledge of your password is required to access the repository.
Losing your password means that your data is irrecoverably lost.
Other backends like sftp and s3 are `described in a later
section <#create-an-sftp-repository>`__ of this document.
Remembering your password is important! If you lose it, you won't be
able to access data stored in the repository.
For automated backups, restic accepts the repository location in the
environment variable ``RESTIC_REPOSITORY``. The password can be read
from a file (via the option ``--password-file``) or the environment
variable ``RESTIC_PASSWORD``.
SFTP
~~~~
In order to backup data via SFTP, you must first set up a server with
SSH and let it know your public key. Passwordless login is really
important since restic fails to connect to the repository if the server
prompts for credentials.
Once the server is configured, the setup of the SFTP repository can
simply be achieved by changing the URL scheme in the ``init`` command:
.. code:: console
$ restic -r sftp:user@host:/tmp/backup init
enter password for new backend:
enter password again:
created restic backend f1c6108821 at sftp:user@host:/tmp/backup
Please note that knowledge of your password is required to access the repository.
Losing your password means that your data is irrecoverably lost.
You can also specify a relative (read: no slash (``/``) character at the
beginning) directory, in this case the dir is relative to the remote
user's home directory.
The backend config string does not allow specifying a port. If you need
to contact an sftp server on a different port, you can create an entry
in the ``ssh`` file, usually located in your user's home directory at
``~/.ssh/config`` or in ``/etc/ssh/ssh_config``:
::
Host foo
User bar
Port 2222
Then use the specified host name ``foo`` normally (you don't need to
specify the user name in this case):
::
$ restic -r sftp:foo:/tmp/backup init
You can also add an entry with a special host name which does not exist,
just for use with restic, and use the ``Hostname`` option to set the
real host name:
::
Host restic-backup-host
Hostname foo
User bar
Port 2222
Then use it in the backend specification:
::
$ restic -r sftp:restic-backup-host:/tmp/backup init
Last, if you'd like to use an entirely different program to create the
SFTP connection, you can specify the command to be run with the option
``-o sftp.command="foobar"``.
REST Server
~~~~~~~~~~~
In order to backup data to the remote server via HTTP or HTTPS protocol,
you must first set up a remote `REST
server <https://github.com/restic/rest-server>`__ instance. Once the
server is configured, accessing it is achieved by changing the URL
scheme like this:
.. code:: console
$ restic -r rest:http://host:8000/
Depending on your REST server setup, you can use HTTPS protocol,
password protection, or multiple repositories. Or any combination of
those features, as you see fit. TCP/IP port is also configurable. Here
are some more examples:
.. code:: console
$ restic -r rest:https://host:8000/
$ restic -r rest:https://user:pass@host:8000/
$ restic -r rest:https://user:pass@host:8000/my_backup_repo/
If you use TLS, make sure your certificates are signed, 'cause restic
client will refuse to communicate otherwise. It's easy to obtain such
certificates today, thanks to free certificate authorities like `Let’s
Encrypt <https://letsencrypt.org/>`__.
REST server uses exactly the same directory structure as local backend,
so you should be able to access it both locally and via HTTP, even
simultaneously.
Amazon S3
~~~~~~~~~
Restic can backup data to any Amazon S3 bucket. However, in this case,
changing the URL scheme is not enough since Amazon uses special security
credentials to sign HTTP requests. By consequence, you must first setup
the following environment variables with the credentials you obtained
while creating the bucket.
.. code:: console
$ export AWS_ACCESS_KEY_ID=<MY_ACCESS_KEY>
$ export AWS_SECRET_ACCESS_KEY=<MY_SECRET_ACCESS_KEY>
You can then easily initialize a repository that uses your Amazon S3 as
a backend, if the bucket does not exist yet it will be created in the
default location:
.. code:: console
$ restic -r s3:s3.amazonaws.com/bucket_name init
enter password for new backend:
enter password again:
created restic backend eefee03bbd at s3:s3.amazonaws.com/bucket_name
Please note that knowledge of your password is required to access the repository.
Losing your password means that your data is irrecoverably lost.
It is not possible at the moment to have restic create a new bucket in a
different location, so you need to create it using a different program.
Afterwards, the S3 server (``s3.amazonaws.com``) will redirect restic to
the correct endpoint.
For an S3-compatible server that is not Amazon (like Minio, see below),
or is only available via HTTP, you can specify the URL to the server
like this: ``s3:http://server:port/bucket_name``.
Minio Server
~~~~~~~~~~~~
`Minio <https://www.minio.io>`__ is an Open Source Object Storage,
written in Go and compatible with AWS S3 API.
- Download and Install `Minio
Server <https://minio.io/downloads/#minio-server>`__.
- You can also refer to https://docs.minio.io for step by step guidance
on installation and getting started on Minio Client and Minio Server.
You must first setup the following environment variables with the
credentials of your running Minio Server.
.. code:: console
$ export AWS_ACCESS_KEY_ID=<YOUR-MINIO-ACCESS-KEY-ID>
$ export AWS_SECRET_ACCESS_KEY= <YOUR-MINIO-SECRET-ACCESS-KEY>
Now you can easily initialize restic to use Minio server as backend with
this command.
.. code:: console
$ ./restic -r s3:http://localhost:9000/restic init
enter password for new backend:
enter password again:
created restic backend 6ad29560f5 at s3:http://localhost:9000/restic1
Please note that knowledge of your password is required to access
the repository. Losing your password means that your data is irrecoverably lost.
Password prompt on Windows
~~~~~~~~~~~~~~~~~~~~~~~~~~
At the moment, restic only supports the default Windows console
interaction. If you use emulation environments like
`MSYS2 <https://msys2.github.io/>`__ or
`Cygwin <https://www.cygwin.com/>`__, which use terminals like
``Mintty`` or ``rxvt``, you may get a password error:
You can workaround this by using a special tool called ``winpty`` (look
`here <https://sourceforge.net/p/msys2/wiki/Porting/>`__ and
`here <https://github.com/rprichard/winpty>`__ for detail information).
On MSYS2, you can install ``winpty`` as follows:
.. code:: console
$ pacman -S winpty
$ winpty restic -r /tmp/backup init
Create a snapshot
-----------------
Now we're ready to backup some data. The contents of a directory at a
specific point in time is called a "snapshot" in restic. Run the
following command and enter the repository password you chose above
again:
.. code:: console
$ restic -r /tmp/backup backup ~/work
enter password for repository:
scan [/home/user/work]
scanned 764 directories, 1816 files in 0:00
[0:29] 100.00% 54.732 MiB/s 1.582 GiB / 1.582 GiB 2580 / 2580 items 0 errors ETA 0:00
duration: 0:29, 54.47MiB/s
snapshot 40dc1520 saved
As you can see, restic created a backup of the directory and was pretty
fast! The specific snapshot just created is identified by a sequence of
hexadecimal characters, ``40dc1520`` in this case.
If you run the command again, restic will create another snapshot of
your data, but this time it's even faster. This is de-duplication at
work!
.. code:: console
$ restic -r /tmp/backup backup ~/shared/work/web
enter password for repository:
using parent snapshot 40dc1520aa6a07b7b3ae561786770a01951245d2367241e71e9485f18ae8228c
scan [/home/user/work]
scanned 764 directories, 1816 files in 0:00
[0:00] 100.00% 0B/s 1.582 GiB / 1.582 GiB 2580 / 2580 items 0 errors ETA 0:00
duration: 0:00, 6572.38MiB/s
snapshot 79766175 saved
You can even backup individual files in the same repository.
.. code:: console
$ restic -r /tmp/backup backup ~/work.txt
scan [~/work.txt]
scanned 0 directories, 1 files in 0:00
[0:00] 100.00% 0B/s 220B / 220B 1 / 1 items 0 errors ETA 0:00
duration: 0:00, 0.03MiB/s
snapshot 31f7bd63 saved
In fact several hosts may use the same repository to backup directories
and files leading to a greater de-duplication.
Please be aware that when you backup different directories (or the
directories to be saved have a variable name component like a
time/date), restic always needs to read all files and only afterwards
can compute which parts of the files need to be saved. When you backup
the same directory again (maybe with new or changed files) restic will
find the old snapshot in the repo and by default only reads those files
that are new or have been modified since the last snapshot. This is
decided based on the modify date of the file in the file system.
You can exclude folders and files by specifying exclude-patterns. Either
specify them with multiple ``--exclude``'s or one ``--exclude-file``
.. code:: console
$ cat exclude
# exclude go-files
*.go
# exclude foo/x/y/z/bar foo/x/bar foo/bar
foo/**/bar
$ restic -r /tmp/backup backup ~/work --exclude=*.c --exclude-file=exclude
Patterns use
```filepath.Glob`` <https://golang.org/pkg/path/filepath/#Glob>`__
internally, see
```filepath.Match`` <https://golang.org/pkg/path/filepath/#Match>`__ for
syntax. Additionally ``**`` excludes arbitrary subdirectories.
Environment-variables in exclude-files are expanded with
```os.ExpandEnv`` <https://golang.org/pkg/os/#ExpandEnv>`__.
By specifying the option ``--one-file-system`` you can instruct restic
to only backup files from the file systems the initially specified files
or directories reside on. For example, calling restic like this won't
backup ``/sys`` or ``/dev`` on a Linux system:
.. code:: console
$ restic -r /tmp/backup backup --one-file-system /
By using the ``--files-from`` option you can read the files you want to
backup from a file. This is especially useful if a lot of files have to
be backed up that are not in the same folder or are maybe pre-filtered
by other software.
For example maybe you want to backup files that have a certain filename
in them:
.. code:: console
$ find /tmp/somefiles | grep 'PATTERN' > /tmp/files_to_backup
You can then use restic to backup the filtered files:
.. code:: console
$ restic -r /tmp/backup backup --files-from /tmp/files_to_backup
Incidentally you can also combine ``--files-from`` with the normal files
args:
.. code:: console
$ restic -r /tmp/backup backup --files-from /tmp/files_to_backup /tmp/some_additional_file
Reading data from stdin
~~~~~~~~~~~~~~~~~~~~~~~
Sometimes it can be nice to directly save the output of a program, e.g.
``mysqldump`` so that the SQL can later be restored. Restic supports
this mode of operation, just supply the option ``--stdin`` to the
``backup`` command like this:
.. code:: console
$ mysqldump [...] | restic -r /tmp/backup backup --stdin
This creates a new snapshot of the output of ``mysqldump``. You can then
use e.g. the fuse mounting option (see below) to mount the repository
and read the file.
By default, the file name ``stdin`` is used, a different name can be
specified with ``--stdin-filename``, e.g. like this:
.. code:: console
$ mysqldump [...] | restic -r /tmp/backup backup --stdin --stdin-filename production.sql
Tags
~~~~
Snapshots can have one or more tags, short strings which add identifying
information. Just specify the tags for a snapshot with ``--tag``:
.. code:: console
$ restic -r /tmp/backup backup --tag projectX ~/shared/work/web
[...]
The tags can later be used to keep (or forget) snapshots.
List all snapshots
------------------
Now, you can list all the snapshots stored in the repository:
.. code:: console
$ restic -r /tmp/backup snapshots
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
40dc1520 2015-05-08 21:38:30 kasimir /home/user/work
79766175 2015-05-08 21:40:19 kasimir /home/user/work
bdbd3439 2015-05-08 21:45:17 luigi /home/art
590c8fc8 2015-05-08 21:47:38 kazik /srv
9f0bc19e 2015-05-08 21:46:11 luigi /srv
You can filter the listing by directory path:
.. code:: console
$ restic -r /tmp/backup snapshots --path="/srv"
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
590c8fc8 2015-05-08 21:47:38 kazik /srv
9f0bc19e 2015-05-08 21:46:11 luigi /srv
Or filter by host:
.. code:: console
$ restic -r /tmp/backup snapshots --host luigi
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
bdbd3439 2015-05-08 21:45:17 luigi /home/art
9f0bc19e 2015-05-08 21:46:11 luigi /srv
Combining filters is also possible.
Restore a snapshot
------------------
Restoring a snapshot is as easy as it sounds, just use the following
command to restore the contents of the latest snapshot to
``/tmp/restore-work``:
.. code:: console
$ restic -r /tmp/backup restore 79766175 --target ~/tmp/restore-work
enter password for repository:
restoring <Snapshot of [/home/user/work] at 2015-05-08 21:40:19.884408621 +0200 CEST> to /tmp/restore-work
Use the word ``latest`` to restore the last backup. You can also combine
``latest`` with the ``--host`` and ``--path`` filters to choose the last
backup for a specific host, path or both.
.. code:: console
$ restic -r /tmp/backup restore latest --target ~/tmp/restore-work --path "/home/art" --host luigi
enter password for repository:
restoring <Snapshot of [/home/art] at 2015-05-08 21:45:17.884408621 +0200 CEST> to /tmp/restore-work
Manage repository keys
----------------------
The ``key`` command allows you to set multiple access keys or passwords
per repository. In fact, you can use the ``list``, ``add``, ``remove``
and ``passwd`` sub-commands to manage these keys very precisely:
.. code:: console
$ restic -r /tmp/backup key list
enter password for repository:
ID User Host Created
----------------------------------------------------------------------
*eb78040b username kasimir 2015-08-12 13:29:57
$ restic -r /tmp/backup key add
enter password for repository:
enter password for new key:
enter password again:
saved new key as <Key of username@kasimir, created on 2015-08-12 13:35:05.316831933 +0200 CEST>
$ restic -r backup key list
enter password for repository:
ID User Host Created
----------------------------------------------------------------------
5c657874 username kasimir 2015-08-12 13:35:05
*eb78040b username kasimir 2015-08-12 13:29:57
Manage tags
-----------
Managing tags on snapshots is done with the ``tag`` command. The
existing set of tags can be replaced completely, tags can be added to
removed. The result is directly visible in the ``snapshots`` command.
Let's say we want to tag snapshot ``590c8fc8`` with the tags ``NL`` and
``CH`` and remove all other tags that may be present, the following
command does that:
.. code:: console
$ restic -r /tmp/backup tag --set NL,CH 590c8fc8
Create exclusive lock for repository
Modified tags on 1 snapshots
Note the snapshot ID has changed, so between each change we need to look
up the new ID of the snapshot. But there is an even better way, the
``tag`` command accepts ``--tag`` for a filter, so we can filter
snapshots based on the tag we just added.
So we can add and remove tags incrementally like this:
.. code:: console
$ restic -r /tmp/backup tag --tag NL --remove CH
Create exclusive lock for repository
Modified tags on 1 snapshots
$ restic -r /tmp/backup tag --tag NL --add UK
Create exclusive lock for repository
Modified tags on 1 snapshots
$ restic -r /tmp/backup tag --tag NL --remove NL
Create exclusive lock for repository
Modified tags on 1 snapshots
$ restic -r /tmp/backup tag --tag NL --add SOMETHING
No snapshots were modified
Check integrity and consistency
-------------------------------
Imagine your repository is saved on a server that has a faulty hard
drive, or even worse, attackers get privileged access and modify your
backup with the intention to make you restore malicious data:
.. code:: console
$ sudo echo "boom" >> backup/index/d795ffa99a8ab8f8e42cec1f814df4e48b8f49129360fb57613df93739faee97
In order to detect these things, it is a good idea to regularly use the
``check`` command to test whether everything is alright, your precious
backup data is consistent and the integrity is unharmed:
.. code:: console
$ restic -r /tmp/backup check
Load indexes
ciphertext verification failed
Trying to restore a snapshot which has been modified as shown above will
yield the same error:
.. code:: console
$ restic -r /tmp/backup restore 79766175 --target ~/tmp/restore-work
Load indexes
ciphertext verification failed
Mount a repository
------------------
Browsing your backup as a regular file system is also very easy. First,
create a mount point such as ``/mnt/restic`` and then use the following
command to serve the repository with FUSE:
.. code:: console
$ mkdir /mnt/restic
$ restic -r /tmp/backup mount /mnt/restic
enter password for repository:
Now serving /tmp/backup at /tmp/restic
Don't forget to umount after quitting!
Mounting repositories via FUSE is not possible on Windows and OpenBSD.
Restic supports storage and preservation of hard links. However, since
hard links exist in the scope of a filesystem by definition, restoring
hard links from a fuse mount should be done by a program that preserves
hard links. A program that does so is rsync, used with the option
--hard-links.
Removing old snapshots
----------------------
All backup space is finite, so restic allows removing old snapshots.
This can be done either manually (by specifying a snapshot ID to remove)
or by using a policy that describes which snapshots to forget. For all
remove operations, two commands need to be called in sequence:
``forget`` to remove a snapshot and ``prune`` to actually remove the
data that was referenced by the snapshot from the repository. This can
be automated with the ``--prune`` option of the ``forget`` command,
which runs ``prune`` automatically if snapshots have been removed.
Remove a single snapshot
~~~~~~~~~~~~~~~~~~~~~~~~
The command ``snapshots`` can be used to list all snapshots in a
repository like this:
.. code:: console
$ restic -r /tmp/backup snapshots
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
40dc1520 2015-05-08 21:38:30 kasimir /home/user/work
79766175 2015-05-08 21:40:19 kasimir /home/user/work
bdbd3439 2015-05-08 21:45:17 luigi /home/art
590c8fc8 2015-05-08 21:47:38 kazik /srv
9f0bc19e 2015-05-08 21:46:11 luigi /srv
In order to remove the snapshot of ``/home/art``, use the ``forget``
command and specify the snapshot ID on the command line:
.. code:: console
$ restic -r /tmp/backup forget bdbd3439
enter password for repository:
removed snapshot d3f01f63
Afterwards this snapshot is removed:
.. code:: console
$ restic -r /tmp/backup snapshots
enter password for repository:
ID Date Host Tags Directory
----------------------------------------------------------------------
40dc1520 2015-05-08 21:38:30 kasimir /home/user/work
79766175 2015-05-08 21:40:19 kasimir /home/user/work
590c8fc8 2015-05-08 21:47:38 kazik /srv
9f0bc19e 2015-05-08 21:46:11 luigi /srv
But the data that was referenced by files in this snapshot is still
stored in the repository. To cleanup unreferenced data, the ``prune``
command must be run:
.. code:: console
$ restic -r /tmp/backup prune
enter password for repository:
counting files in repo
building new index for repo
[0:00] 100.00% 22 / 22 files
repository contains 22 packs (8512 blobs) with 100.092 MiB bytes
processed 8512 blobs: 0 duplicate blobs, 0B duplicate
load all snapshots
find data that is still in use for 1 snapshots
[0:00] 100.00% 1 / 1 snapshots
found 8433 of 8512 data blobs still in use
will rewrite 3 packs
creating new index
[0:00] 86.36% 19 / 22 files
saved new index as 544a5084
done
Afterwards the repository is smaller.
You can automate this two-step process by using the ``--prune`` switch
to ``forget``:
.. code:: console
$ restic forget --keep-last 1 --prune
snapshots for host mopped, directories /home/user/work:
keep 1 snapshots:
ID Date Host Tags Directory
----------------------------------------------------------------------
4bba301e 2017-02-21 10:49:18 mopped /home/user/work
remove 1 snapshots:
ID Date Host Tags Directory
----------------------------------------------------------------------
8c02b94b 2017-02-21 10:48:33 mopped /home/user/work
1 snapshots have been removed, running prune
counting files in repo
building new index for repo
[0:00] 100.00% 37 / 37 packs
repository contains 37 packs (5521 blobs) with 151.012 MiB bytes
processed 5521 blobs: 0 duplicate blobs, 0B duplicate
load all snapshots
find data that is still in use for 1 snapshots
[0:00] 100.00% 1 / 1 snapshots
found 5323 of 5521 data blobs still in use, removing 198 blobs
will delete 0 packs and rewrite 27 packs, this frees 22.106 MiB
creating new index
[0:00] 100.00% 30 / 30 packs
saved new index as b49f3e68
done
Removing snapshots according to a policy
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Removing snapshots manually is tedious and error-prone, therefore restic
allows specifying which snapshots should be removed automatically
according to a policy. You can specify how many hourly, daily, weekly,
monthly and yearly snapshots to keep, any other snapshots are removed.
The most important command-line parameter here is ``--dry-run`` which
instructs restic to not remove anything but print which snapshots would
be removed.
When ``forget`` is run with a policy, restic loads the list of all
snapshots, then groups these by host name and list of directories. The
policy is then applied to each group of snapshots separately. This is a
safety feature.
The ``forget`` command accepts the following parameters:
- ``--keep-last n`` never delete the ``n`` last (most recent) snapshots
- ``--keep-hourly n`` for the last ``n`` hours in which a snapshot was
made, keep only the last snapshot for each hour.
- ``--keep-daily n`` for the last ``n`` days which have one or more
snapshots, only keep the last one for that day.
- ``--keep-weekly n`` for the last ``n`` weeks which have one or more
snapshots, only keep the last one for that week.
- ``--keep-monthly n`` for the last ``n`` months which have one or more
snapshots, only keep the last one for that month.
- ``--keep-yearly n`` for the last ``n`` years which have one or more
snapshots, only keep the last one for that year.
- ``--keep-tag`` keep all snapshots which have all tags specified by
this option (can be specified multiple times).
Additionally, you can restrict removing snapshots to those which have a
particular hostname with the ``--hostname`` parameter, or tags with the
``--tag`` option. When multiple tags are specified, only the snapshots
which have all the tags are considered.
All the ``--keep-*`` options above only count
hours/days/weeks/months/years which have a snapshot, so those without a
snapshot are ignored.
Let's explain this with an example: Suppose you have only made a backup
on each Sunday for 12 weeks. Then ``forget --keep-daily 4`` will keep
the last four snapshots for the last four Sundays, but remove the rest.
Only counting the days which have a backup and ignore the ones without
is a safety feature: it prevents restic from removing many snapshots
when no new ones are created. If it was implemented otherwise, running
``forget --keep-daily 4`` on a Friday would remove all snapshots!
Debugging
---------
The program can be built with debug support like this:
.. code:: console
$ go run build.go -tags debug
Afterwards, extensive debug messages are written to the file in
environment variable ``DEBUG_LOG``, e.g.:
.. code:: console
$ DEBUG_LOG=/tmp/restic-debug.log restic backup ~/work
If you suspect that there is a bug, you can have a look at the debug
log. Please be aware that the debug log might contain sensitive
information such as file and directory names.
The debug log will always contain all log messages restic generates. You
can also instruct restic to print some or all debug messages to stderr.
These can also be limited to e.g. a list of source files or a list of
patterns for function names. The patterns are globbing patterns (see the
documentation for
```path.Glob`` <https://golang.org/pkg/path/#Glob>`__), multiple
patterns are separated by commas. Patterns are case sensitive.
Printing all log messages to the console can be achieved by setting the
file filter to ``*``:
.. code:: console
$ DEBUG_FILES=* restic check
If you want restic to just print all debug log messages from the files
``main.go`` and ``lock.go``, set the environment variable
``DEBUG_FILES`` like this:
.. code:: console
$ DEBUG_FILES=main.go,lock.go restic check
The following command line instructs restic to only print debug
statements originating in functions that match the pattern ``*unlock*``
(case sensitive):
.. code:: console
$ DEBUG_FUNCS=*unlock* restic check
Under the hood: Browse repository objects
-----------------------------------------
Internally, a repository stores data of several different types
described in the `design
documentation <https://github.com/restic/restic/blob/master/doc/Design.md>`__.
You can ``list`` objects such as blobs, packs, index, snapshots, keys or
locks with the following command:
.. code:: console
$ restic -r /tmp/backup list snapshots
d369ccc7d126594950bf74f0a348d5d98d9e99f3215082eb69bf02dc9b3e464c
The ``find`` command searches for a given
`pattern <http://golang.org/pkg/path/filepath/#Match>`__ in the
repository.
.. code:: console
$ restic -r backup find test.txt
debug log file restic.log
debug enabled
enter password for repository:
found 1 matching entries in snapshot 196bc5760c909a7681647949e80e5448e276521489558525680acf1bd428af36
-rw-r--r-- 501 20 5 2015-08-26 14:09:57 +0200 CEST path/to/test.txt
The ``cat`` command allows you to display the JSON representation of the
objects or its raw content.
.. code:: console
$ restic -r /tmp/backup cat snapshot d369ccc7d126594950bf74f0a348d5d98d9e99f3215082eb69bf02dc9b3e464c
enter password for repository:
{
"time": "2015-08-12T12:52:44.091448856+02:00",
"tree": "05cec17e8d3349f402576d02576a2971fc0d9f9776ce2f441c7010849c4ff5af",
"paths": [
"/home/user/work"
],
"hostname": "kasimir",
"username": "username",
"uid": 501,
"gid": 20
}
Scripting
---------
Restic supports the output of some commands in JSON format, the JSON
data can then be processed by other programs (e.g.
`jq <https://stedolan.github.io/jq/>`__). The following example
lists all snapshots as JSON and uses ``jq`` to pretty-print the result:
.. code:: console
$ restic -r /tmp/backup snapshots --json | jq .
[
{
"time": "2017-03-11T09:57:43.26630619+01:00",
"tree": "bf25241679533df554fc0fd0ae6dbb9dcf1859a13f2bc9dd4543c354eff6c464",
"paths": [
"/home/work/doc"
],
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"id": "bbeed6d28159aa384d1ccc6fa0b540644b1b9599b162d2972acda86b1b80f89e"
},
{
"time": "2017-03-11T09:58:57.541446938+01:00",
"tree": "7f8c95d3420baaac28dc51609796ae0e0ecfb4862b609a9f38ffaf7ae2d758da",
"paths": [
"/home/user/shared"
],
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"id": "b157d91c16f0ba56801ece3a708dfc53791fe2a97e827090d6ed9a69a6ebdca0"
}
]
Temporary files
---------------
During some operations (e.g. ``backup`` and ``prune``) restic uses
temporary files to store data. These files will, by default, be saved to
the system's temporary directory, on Linux this is usually located in
``/tmp/``. The environment variable ``TMPDIR`` can be used to specify a
different directory, e.g. to use the directory ``/var/tmp/restic-tmp``
instead of the default, set the environment variable like this:
.. code:: console
$ export TMPDIR=/var/tmp/restic-tmp
$ restic -r /tmp/backup backup ~/work

6
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==========
References
==========
.. include:: references/design.rst
.. include:: references/rest_backend.rst

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Design
======
Terminology
-----------
This section introduces terminology used in this document.
*Repository*: All data produced during a backup is sent to and stored in
a repository in a structured form, for example in a file system
hierarchy with several subdirectories. A repository implementation must
be able to fulfill a number of operations, e.g. list the contents.
*Blob*: A Blob combines a number of data bytes with identifying
information like the SHA-256 hash of the data and its length.
*Pack*: A Pack combines one or more Blobs, e.g. in a single file.
*Snapshot*: A Snapshot stands for the state of a file or directory that
has been backed up at some point in time. The state here means the
content and meta data like the name and modification time for the file
or the directory and its contents.
*Storage ID*: A storage ID is the SHA-256 hash of the content stored in
the repository. This ID is required in order to load the file from the
repository.
Repository Format
-----------------
All data is stored in a restic repository. A repository is able to store
data of several different types, which can later be requested based on
an ID. This so-called "storage ID" is the SHA-256 hash of the content of
a file. All files in a repository are only written once and never
modified afterwards. This allows accessing and even writing to the
repository with multiple clients in parallel. Only the delete operation
removes data from the repository.
Repositories consist of several directories and a top-level file called
``config``. For all other files stored in the repository, the name for
the file is the lower case hexadecimal representation of the storage ID,
which is the SHA-256 hash of the file's contents. This allows for easy
verification of files for accidental modifications, like disk read
errors, by simply running the program ``sha256sum`` on the file and
comparing its output to the file name. If the prefix of a filename is
unique amongst all the other files in the same directory, the prefix may
be used instead of the complete filename.
Apart from the files stored within the ``keys`` directory, all files are
encrypted with AES-256 in counter mode (CTR). The integrity of the
encrypted data is secured by a Poly1305-AES message authentication code
(sometimes also referred to as a "signature").
In the first 16 bytes of each encrypted file the initialisation vector
(IV) is stored. It is followed by the encrypted data and completed by
the 16 byte MAC. The format is: ``IV || CIPHERTEXT || MAC``. The
complete encryption overhead is 32 bytes. For each file, a new random IV
is selected.
The file ``config`` is encrypted this way and contains a JSON document
like the following:
.. code:: json
{
"version": 1,
"id": "5956a3f67a6230d4a92cefb29529f10196c7d92582ec305fd71ff6d331d6271b",
"chunker_polynomial": "25b468838dcb75"
}
After decryption, restic first checks that the version field contains a
version number that it understands, otherwise it aborts. At the moment,
the version is expected to be 1. The field ``id`` holds a unique ID
which consists of 32 random bytes, encoded in hexadecimal. This uniquely
identifies the repository, regardless if it is accessed via SFTP or
locally. The field ``chunker_polynomial`` contains a parameter that is
used for splitting large files into smaller chunks (see below).
Filesystem-Based Repositories
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The ``local`` and ``sftp`` backends are implemented using files and
directories stored in a file system. The directory layout is the same
for both backend types.
The basic layout of a repository stored in a ``local`` or ``sftp``
backend is shown here:
::
/tmp/restic-repo
├── config
├── data
│ ├── 21
│ │ └── 2159dd48f8a24f33c307b750592773f8b71ff8d11452132a7b2e2a6a01611be1
│ ├── 32
│ │ └── 32ea976bc30771cebad8285cd99120ac8786f9ffd42141d452458089985043a5
│ ├── 59
│ │ └── 59fe4bcde59bd6222eba87795e35a90d82cd2f138a27b6835032b7b58173a426
│ ├── 73
│ │ └── 73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c
│ [...]
├── index
│ ├── c38f5fb68307c6a3e3aa945d556e325dc38f5fb68307c6a3e3aa945d556e325d
│ └── ca171b1b7394d90d330b265d90f506f9984043b342525f019788f97e745c71fd
├── keys
│ └── b02de829beeb3c01a63e6b25cbd421a98fef144f03b9a02e46eff9e2ca3f0bd7
├── locks
├── snapshots
│ └── 22a5af1bdc6e616f8a29579458c49627e01b32210d09adb288d1ecda7c5711ec
└── tmp
A local repository can be initialized with the ``restic init`` command,
e.g.:
.. code:: console
$ restic -r /tmp/restic-repo init
The local and sftp backends will also accept the repository layout
described in the following section, so that remote repositories mounted
locally e.g. via fuse can be accessed. The layout auto-detection can be
overridden by specifying the option ``-o local.layout=default``, valid
values are ``default``, ``cloud`` and ``s3``. The option for the sftp
backend is named ``sftp.layout``.
Object-Storage-Based Repositories
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Repositories in a backend based on an object store (e.g. Amazon s3) have
the same basic layout, with the exception that all data pack files are
directly saved in the ``data`` path, without the sub-directories listed
for the filesystem-based backends as listed in the previous section. The
layout looks like this:
::
/config
/data
├── 2159dd48f8a24f33c307b750592773f8b71ff8d11452132a7b2e2a6a01611be1
├── 32ea976bc30771cebad8285cd99120ac8786f9ffd42141d452458089985043a5
├── 59fe4bcde59bd6222eba87795e35a90d82cd2f138a27b6835032b7b58173a426
├── 73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c
[...]
/index
├── c38f5fb68307c6a3e3aa945d556e325dc38f5fb68307c6a3e3aa945d556e325d
└── ca171b1b7394d90d330b265d90f506f9984043b342525f019788f97e745c71fd
/keys
└── b02de829beeb3c01a63e6b25cbd421a98fef144f03b9a02e46eff9e2ca3f0bd7
/locks
/snapshots
└── 22a5af1bdc6e616f8a29579458c49627e01b32210d09adb288d1ecda7c5711ec
Unfortunately during development the s3 backend uses slightly different
paths (directory names use singular instead of plural for ``key``,
``lock``, and ``snapshot`` files), for s3 the repository layout looks
like this:
::
/config
/data
├── 2159dd48f8a24f33c307b750592773f8b71ff8d11452132a7b2e2a6a01611be1
├── 32ea976bc30771cebad8285cd99120ac8786f9ffd42141d452458089985043a5
├── 59fe4bcde59bd6222eba87795e35a90d82cd2f138a27b6835032b7b58173a426
├── 73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c
[...]
/index
├── c38f5fb68307c6a3e3aa945d556e325dc38f5fb68307c6a3e3aa945d556e325d
└── ca171b1b7394d90d330b265d90f506f9984043b342525f019788f97e745c71fd
/key
└── b02de829beeb3c01a63e6b25cbd421a98fef144f03b9a02e46eff9e2ca3f0bd7
/lock
/snapshot
└── 22a5af1bdc6e616f8a29579458c49627e01b32210d09adb288d1ecda7c5711ec
The s3 backend understands and accepts both forms, new backends are
always created with the former layout for compatibility reasons.
Pack Format
-----------
All files in the repository except Key and Pack files just contain raw
data, stored as ``IV || Ciphertext || MAC``. Pack files may contain one
or more Blobs of data.
A Pack's structure is as follows:
::
EncryptedBlob1 || ... || EncryptedBlobN || EncryptedHeader || Header_Length
At the end of the Pack file is a header, which describes the content.
The header is encrypted and authenticated. ``Header_Length`` is the
length of the encrypted header encoded as a four byte integer in
little-endian encoding. Placing the header at the end of a file allows
writing the blobs in a continuous stream as soon as they are read during
the backup phase. This reduces code complexity and avoids having to
re-write a file once the pack is complete and the content and length of
the header is known.
All the blobs (``EncryptedBlob1``, ``EncryptedBlobN`` etc.) are
authenticated and encrypted independently. This enables repository
reorganisation without having to touch the encrypted Blobs. In addition
it also allows efficient indexing, for only the header needs to be read
in order to find out which Blobs are contained in the Pack. Since the
header is authenticated, authenticity of the header can be checked
without having to read the complete Pack.
After decryption, a Pack's header consists of the following elements:
::
Type_Blob1 || Length(EncryptedBlob1) || Hash(Plaintext_Blob1) ||
[...]
Type_BlobN || Length(EncryptedBlobN) || Hash(Plaintext_Blobn) ||
This is enough to calculate the offsets for all the Blobs in the Pack.
Length is the length of a Blob as a four byte integer in little-endian
format. The type field is a one byte field and labels the content of a
blob according to the following table:
+--------+-----------+
| Type | Meaning |
+========+===========+
| 0 | data |
+--------+-----------+
| 1 | tree |
+--------+-----------+
All other types are invalid, more types may be added in the future.
For reconstructing the index or parsing a pack without an index, first
the last four bytes must be read in order to find the length of the
header. Afterwards, the header can be read and parsed, which yields all
plaintext hashes, types, offsets and lengths of all included blobs.
Indexing
--------
Index files contain information about Data and Tree Blobs and the Packs
they are contained in and store this information in the repository. When
the local cached index is not accessible any more, the index files can
be downloaded and used to reconstruct the index. The files are encrypted
and authenticated like Data and Tree Blobs, so the outer structure is
``IV || Ciphertext || MAC`` again. The plaintext consists of a JSON
document like the following:
.. code:: json
{
"supersedes": [
"ed54ae36197f4745ebc4b54d10e0f623eaaaedd03013eb7ae90df881b7781452"
],
"packs": [
{
"id": "73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c",
"blobs": [
{
"id": "3ec79977ef0cf5de7b08cd12b874cd0f62bbaf7f07f3497a5b1bbcc8cb39b1ce",
"type": "data",
"offset": 0,
"length": 25
},{
"id": "9ccb846e60d90d4eb915848add7aa7ea1e4bbabfc60e573db9f7bfb2789afbae",
"type": "tree",
"offset": 38,
"length": 100
},
{
"id": "d3dc577b4ffd38cc4b32122cabf8655a0223ed22edfd93b353dc0c3f2b0fdf66",
"type": "data",
"offset": 150,
"length": 123
}
]
}, [...]
]
}
This JSON document lists Packs and the blobs contained therein. In this
example, the Pack ``73d04e61`` contains two data Blobs and one Tree
blob, the plaintext hashes are listed afterwards.
The field ``supersedes`` lists the storage IDs of index files that have
been replaced with the current index file. This happens when index files
are repacked, for example when old snapshots are removed and Packs are
recombined.
There may be an arbitrary number of index files, containing information
on non-disjoint sets of Packs. The number of packs described in a single
file is chosen so that the file size is kept below 8 MiB.
Keys, Encryption and MAC
------------------------
All data stored by restic in the repository is encrypted with AES-256 in
counter mode and authenticated using Poly1305-AES. For encrypting new
data first 16 bytes are read from a cryptographically secure
pseudorandom number generator as a random nonce. This is used both as
the IV for counter mode and the nonce for Poly1305. This operation needs
three keys: A 32 byte for AES-256 for encryption, a 16 byte AES key and
a 16 byte key for Poly1305. For details see the original paper `The
Poly1305-AES message-authentication
code <http://cr.yp.to/mac/poly1305-20050329.pdf>`__ by Dan Bernstein.
The data is then encrypted with AES-256 and afterwards a message
authentication code (MAC) is computed over the ciphertext, everything is
then stored as IV \|\| CIPHERTEXT \|\| MAC.
The directory ``keys`` contains key files. These are simple JSON
documents which contain all data that is needed to derive the
repository's master encryption and message authentication keys from a
user's password. The JSON document from the repository can be
pretty-printed for example by using the Python module ``json``
(shortened to increase readability):
::
$ python -mjson.tool /tmp/restic-repo/keys/b02de82*
{
"hostname": "kasimir",
"username": "fd0"
"kdf": "scrypt",
"N": 65536,
"r": 8,
"p": 1,
"created": "2015-01-02T18:10:13.48307196+01:00",
"data": "tGwYeKoM0C4j4/9DFrVEmMGAldvEn/+iKC3te/QE/6ox/V4qz58FUOgMa0Bb1cIJ6asrypCx/Ti/pRXCPHLDkIJbNYd2ybC+fLhFIJVLCvkMS+trdywsUkglUbTbi+7+Ldsul5jpAj9vTZ25ajDc+4FKtWEcCWL5ICAOoTAxnPgT+Lh8ByGQBH6KbdWabqamLzTRWxePFoYuxa7yXgmj9A==",
"salt": "uW4fEI1+IOzj7ED9mVor+yTSJFd68DGlGOeLgJELYsTU5ikhG/83/+jGd4KKAaQdSrsfzrdOhAMftTSih5Ux6w==",
}
When the repository is opened by restic, the user is prompted for the
repository password. This is then used with ``scrypt``, a key derivation
function (KDF), and the supplied parameters (``N``, ``r``, ``p`` and
``salt``) to derive 64 key bytes. The first 32 bytes are used as the
encryption key (for AES-256) and the last 32 bytes are used as the
message authentication key (for Poly1305-AES). These last 32 bytes are
divided into a 16 byte AES key ``k`` followed by 16 bytes of secret key
``r``. The key ``r`` is then masked for use with Poly1305 (see the paper
for details).
Those message authentication keys (``k`` and ``r``) are used to compute
a MAC over the bytes contained in the JSON field ``data`` (after
removing the Base64 encoding and not including the last 32 byte). If the
password is incorrect or the key file has been tampered with, the
computed MAC will not match the last 16 bytes of the data, and restic
exits with an error. Otherwise, the data is decrypted with the
encryption key derived from ``scrypt``. This yields a JSON document
which contains the master encryption and message authentication keys for
this repository (encoded in Base64). The command
``restic cat masterkey`` can be used as follows to decrypt and
pretty-print the master key:
.. code:: console
$ restic -r /tmp/restic-repo cat masterkey
{
"mac": {
"k": "evFWd9wWlndL9jc501268g==",
"r": "E9eEDnSJZgqwTOkDtOp+Dw=="
},
"encrypt": "UQCqa0lKZ94PygPxMRqkePTZnHRYh1k1pX2k2lM2v3Q=",
}
All data in the repository is encrypted and authenticated with these
master keys. For encryption, the AES-256 algorithm in Counter mode is
used. For message authentication, Poly1305-AES is used as described
above.
A repository can have several different passwords, with a key file for
each. This way, the password can be changed without having to re-encrypt
all data.
Snapshots
---------
A snapshot represents a directory with all files and sub-directories at
a given point in time. For each backup that is made, a new snapshot is
created. A snapshot is a JSON document that is stored in an encrypted
file below the directory ``snapshots`` in the repository. The filename
is the storage ID. This string is unique and used within restic to
uniquely identify a snapshot.
The command ``restic cat snapshot`` can be used as follows to decrypt
and pretty-print the contents of a snapshot file:
.. code:: console
$ restic -r /tmp/restic-repo cat snapshot 251c2e58
enter password for repository:
{
"time": "2015-01-02T18:10:50.895208559+01:00",
"tree": "2da81727b6585232894cfbb8f8bdab8d1eccd3d8f7c92bc934d62e62e618ffdf",
"dir": "/tmp/testdata",
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"tags": [
"NL"
]
}
Here it can be seen that this snapshot represents the contents of the
directory ``/tmp/testdata``. The most important field is ``tree``. When
the meta data (e.g. the tags) of a snapshot change, the snapshot needs
to be re-encrypted and saved. This will change the storage ID, so in
order to relate these seemingly different snapshots, a field
``original`` is introduced which contains the ID of the original
snapshot, e.g. after adding the tag ``DE`` to the snapshot above it
becomes:
.. code:: console
$ restic -r /tmp/restic-repo cat snapshot 22a5af1b
enter password for repository:
{
"time": "2015-01-02T18:10:50.895208559+01:00",
"tree": "2da81727b6585232894cfbb8f8bdab8d1eccd3d8f7c92bc934d62e62e618ffdf",
"dir": "/tmp/testdata",
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"tags": [
"NL",
"DE"
],
"original": "251c2e5841355f743f9d4ffd3260bee765acee40a6229857e32b60446991b837"
}
Once introduced, the ``original`` field is not modified when the
snapshot's meta data is changed again.
All content within a restic repository is referenced according to its
SHA-256 hash. Before saving, each file is split into variable sized
Blobs of data. The SHA-256 hashes of all Blobs are saved in an ordered
list which then represents the content of the file.
In order to relate these plaintext hashes to the actual location within
a Pack file , an index is used. If the index is not available, the
header of all data Blobs can be read.
Trees and Data
--------------
A snapshot references a tree by the SHA-256 hash of the JSON string
representation of its contents. Trees and data are saved in pack files
in a subdirectory of the directory ``data``.
The command ``restic cat blob`` can be used to inspect the tree
referenced above (piping the output of the command to ``jq .`` so that
the JSON is indented):
.. code:: console
$ restic -r /tmp/restic-repo cat blob b8138ab08a4722596ac89c917827358da4672eac68e3c03a8115b88dbf4bfb59 | jq .
enter password for repository:
{
"nodes": [
{
"name": "testdata",
"type": "dir",
"mode": 493,
"mtime": "2014-12-22T14:47:59.912418701+01:00",
"atime": "2014-12-06T17:49:21.748468803+01:00",
"ctime": "2014-12-22T14:47:59.912418701+01:00",
"uid": 1000,
"gid": 100,
"user": "fd0",
"inode": 409704562,
"content": null,
"subtree": "b26e315b0988ddcd1cee64c351d13a100fedbc9fdbb144a67d1b765ab280b4dc"
}
]
}
A tree contains a list of entries (in the field ``nodes``) which contain
meta data like a name and timestamps. When the entry references a
directory, the field ``subtree`` contains the plain text ID of another
tree object.
When the command ``restic cat blob`` is used, the plaintext ID is needed
to print a tree. The tree referenced above can be dumped as follows:
.. code:: console
$ restic -r /tmp/restic-repo cat blob 8b238c8811cc362693e91a857460c78d3acf7d9edb2f111048691976803cf16e
enter password for repository:
{
"nodes": [
{
"name": "testfile",
"type": "file",
"mode": 420,
"mtime": "2014-12-06T17:50:23.34513538+01:00",
"atime": "2014-12-06T17:50:23.338468713+01:00",
"ctime": "2014-12-06T17:50:23.34513538+01:00",
"uid": 1000,
"gid": 100,
"user": "fd0",
"inode": 416863351,
"size": 1234,
"links": 1,
"content": [
"50f77b3b4291e8411a027b9f9b9e64658181cc676ce6ba9958b95f268cb1109d"
]
},
[...]
]
}
This tree contains a file entry. This time, the ``subtree`` field is not
present and the ``content`` field contains a list with one plain text
SHA-256 hash.
The command ``restic cat blob`` can also be used to extract and decrypt
data given a plaintext ID, e.g. for the data mentioned above:
.. code:: console
$ restic -r /tmp/restic-repo cat blob 50f77b3b4291e8411a027b9f9b9e64658181cc676ce6ba9958b95f268cb1109d | sha256sum
enter password for repository:
50f77b3b4291e8411a027b9f9b9e64658181cc676ce6ba9958b95f268cb1109d -
As can be seen from the output of the program ``sha256sum``, the hash
matches the plaintext hash from the map included in the tree above, so
the correct data has been returned.
Locks
-----
The restic repository structure is designed in a way that allows
parallel access of multiple instance of restic and even parallel writes.
However, there are some functions that work more efficient or even
require exclusive access of the repository. In order to implement these
functions, restic processes are required to create a lock on the
repository before doing anything.
Locks come in two types: Exclusive and non-exclusive locks. At most one
process can have an exclusive lock on the repository, and during that
time there must not be any other locks (exclusive and non-exclusive).
There may be multiple non-exclusive locks in parallel.
A lock is a file in the subdir ``locks`` whose filename is the storage
ID of the contents. It is encrypted and authenticated the same way as
other files in the repository and contains the following JSON structure:
.. code:: json
{
"time": "2015-06-27T12:18:51.759239612+02:00",
"exclusive": false,
"hostname": "kasimir",
"username": "fd0",
"pid": 13607,
"uid": 1000,
"gid": 100
}
The field ``exclusive`` defines the type of lock. When a new lock is to
be created, restic checks all locks in the repository. When a lock is
found, it is tested if the lock is stale, which is the case for locks
with timestamps older than 30 minutes. If the lock was created on the
same machine, even for younger locks it is tested whether the process is
still alive by sending a signal to it. If that fails, restic assumes
that the process is dead and considers the lock to be stale.
When a new lock is to be created and no other conflicting locks are
detected, restic creates a new lock, waits, and checks if other locks
appeared in the repository. Depending on the type of the other locks and
the lock to be created, restic either continues or fails.
Backups and Deduplication
-------------------------
For creating a backup, restic scans the source directory for all files,
sub-directories and other entries. The data from each file is split into
variable length Blobs cut at offsets defined by a sliding window of 64
byte. The implementation uses Rabin Fingerprints for implementing this
Content Defined Chunking (CDC). An irreducible polynomial is selected at
random and saved in the file ``config`` when a repository is
initialized, so that watermark attacks are much harder.
Files smaller than 512 KiB are not split, Blobs are of 512 KiB to 8 MiB
in size. The implementation aims for 1 MiB Blob size on average.
For modified files, only modified Blobs have to be saved in a subsequent
backup. This even works if bytes are inserted or removed at arbitrary
positions within the file.
Threat Model
------------
The design goals for restic include being able to securely store backups
in a location that is not completely trusted, e.g. a shared system where
others can potentially access the files or (in the case of the system
administrator) even modify or delete them.
General assumptions:
- The host system a backup is created on is trusted. This is the most
basic requirement, and essential for creating trustworthy backups.
The restic backup program guarantees the following:
- Accessing the unencrypted content of stored files and metadata should
not be possible without a password for the repository. Everything
except the metadata included for informational purposes in the key
files is encrypted and authenticated.
- Modifications (intentional or unintentional) can be detected
automatically on several layers:
1. For all accesses of data stored in the repository it is checked
whether the cryptographic hash of the contents matches the storage
ID (the file's name). This way, modifications (bad RAM, broken
harddisk) can be detected easily.
2. Before decrypting any data, the MAC on the encrypted data is
checked. If there has been a modification, the MAC check will
fail. This step happens even before the data is decrypted, so data
that has been tampered with is not decrypted at all.
However, the restic backup program is not designed to protect against
attackers deleting files at the storage location. There is nothing that
can be done about this. If this needs to be guaranteed, get a secure
location without any access from third parties. If you assume that
attackers have write access to your files at the storage location,
attackers are able to figure out (e.g. based on the timestamps of the
stored files) which files belong to what snapshot. When only these files
are deleted, the particular snapshot vanished and all snapshots
depending on data that has been added in the snapshot cannot be restored
completely. Restic is not designed to detect this attack.

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REST Backend
============
Restic can interact with HTTP Backend that respects the following REST
API. The following values are valid for ``{type}``: ``data``, ``keys``,
``locks``, ``snapshots``, ``index``, ``config``. ``{path}`` is a path to
the repository, so that multiple different repositories can be accessed.
The default path is ``/``.
POST {path}?create=true
-----------------------
This request is used to initially create a new repository. The server
responds with "200 OK" if the repository structure was created
successfully or already exists, otherwise an error is returned.
DELETE {path}
-------------
Deletes the repository on the server side. The server responds with "200
OK" if the repository was successfully removed. If this function is not
implemented the server returns "501 Not Implemented", if this it is
denied by the server it returns "403 Forbidden".
HEAD {path}/config
------------------
Returns "200 OK" if the repository has a configuration, an HTTP error
otherwise.
GET {path}/config
-----------------
Returns the content of the configuration file if the repository has a
configuration, an HTTP error otherwise.
Response format: binary/octet-stream
POST {path}/config
------------------
Returns "200 OK" if the configuration of the request body has been
saved, an HTTP error otherwise.
GET {path}/{type}/
------------------
Returns a JSON array containing the names of all the blobs stored for a
given type.
Response format: JSON
HEAD {path}/{type}/{name}
-------------------------
Returns "200 OK" if the blob with the given name and type is stored in
the repository, "404 not found" otherwise. If the blob exists, the HTTP
header ``Content-Length`` is set to the file size.
GET {path}/{type}/{name}
------------------------
Returns the content of the blob with the given name and type if it is
stored in the repository, "404 not found" otherwise.
If the request specifies a partial read with a Range header field, then
the status code of the response is 206 instead of 200 and the response
only contains the specified range.
Response format: binary/octet-stream
POST {path}/{type}/{name}
-------------------------
Saves the content of the request body as a blob with the given name and
type, an HTTP error otherwise.
Request format: binary/octet-stream
DELETE {path}/{type}/{name}
---------------------------
Returns "200 OK" if the blob with the given name and type has been
deleted from the repository, an HTTP error otherwise.

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sphinx
sphinx_rtd_theme

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Talks
=====
The following talks will be or have been given about restic:
- 2016-01-31: Lightning Talk at the Go Devroom at FOSDEM 2016,
Brussels, Belgium
- 2016-01-29: `restic - Backups mal
richtig <https://media.ccc.de/v/c4.openchaos.2016.01.restic>`__:
Public lecture in German at `CCC Cologne
e.V. <https://koeln.ccc.de>`__ in Cologne, Germany
- 2015-08-23: `A Solution to the Backup
Inconvenience <https://programm.froscon.de/2015/events/1515.html>`__:
Lecture at `FROSCON 2015 <https://www.froscon.de>`__ in Bonn, Germany
- 2015-02-01: `Lightning Talk at FOSDEM
2015 <https://www.youtube.com/watch?v=oM-MfeflUZ8&t=11m40s>`__: A
short introduction (with slightly outdated command line)
- 2015-01-27: `Talk about restic at CCC
Aachen <https://videoag.fsmpi.rwth-aachen.de/?view=player&lectureid=4442#content>`__
(in German)

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site_name: Documentation for restic
theme: readthedocs
markdown_extensions:
- codehilite:
extra_css:
- code.css
docs_dir: doc
pages:
- Getting Started: index.md
- User Manual: Manual.md
- restic Design Document: Design.md