..
Normally, there are no heading levels assigned to certain characters as the structure is
determined from the succession of headings. However, this convention is used in Python’s
Style Guide for documenting which you may follow:
# with overline, for parts
* for chapters
= for sections
- for subsections
^ for subsubsections
" for paragraphs
########
Examples
########
********************************
Setting up restic with Amazon S3
********************************
Preface
=======
This tutorial will show you how to use restic with Amazon S3. It will show you how
to navigate the AWS web interface, create an S3 bucket, create a user with
access to only this bucket, and finally how to connect restic to this bucket.
Prerequisites
=============
You should already have a ``restic`` binary available on your system that you can
run. Furthermore, you should also have an account with
`AWS `__. You will likely need to provide credit card
details for billing purposes, even if you use their
`free-tier `__.
Logging into AWS
================
Point your browser to
https://console.aws.amazon.com
and log in using your AWS account. You will be presented with the AWS homepage:
.. image:: images/aws_s3/01_aws_start.png
:alt: AWS Homepage
By using the "Services" button in the upper left corder, a menu of all services
provided by AWS can be opened:
.. image:: images/aws_s3/02_aws_menu.png
:alt: AWS Services Menu
For this tutorial, the Simple Storage Service (S3), as well as Identity and
Access Management (IAM) are relevant.
Creating the bucket
===================
First, a bucket to store your backups in must be created. Using the "Services"
menu, navigate to S3. In case you already have some S3 buckets, you will see a
list of them here:
.. image:: images/aws_s3/03_buckets_list_before.png
:alt: List of S3 Buckets
Click the "Create bucket" button and choose a name and region for your new
bucket. For the purpose of this tutorial, the bucket will be named
``restic-demo`` and reside in Frankfurt. Because the bucket name space is
shared among all AWS users, the name ``restic-demo`` may not be available to
you. Be creative and choose a unique bucket name.
.. image:: images/aws_s3/04_bucket_create_start.png
:alt: Create a Bucket
It is not necessary to configure any special properties or permissions of the
bucket just yet. Therefore, just finish the wizard without making any further
changes:
.. image:: images/aws_s3/05_bucket_create_review.png
:alt: Review Bucket Creation
The newly created ``restic-demo`` bucket will now appear on the list of S3
buckets:
.. image:: images/aws_s3/06_buckets_list_after.png
:alt: List With New Bucket
Creating a user
===============
Use the "Services" menu of the AWS web interface to navigate to IAM. This will
bring you to the IAM homepage. To create a new user, click on the "Users" menu
entry on the left:
.. image:: images/aws_s3/07_iam_start.png
:alt: IAM Home Page
In case you already have set-up users with IAM before, you will see a list of
them here. Use the "Add user" button at the top to create a new user:
.. image:: images/aws_s3/08_user_list.png
:alt: IAM User List
For this tutorial, the new user will be named ``restic-demo-user``. Feel free to
choose your own name that best fits your needs. This user will only ever access
AWS through the ``restic`` program and not through the web interface. Therefore,
"Programmatic access" is selected for "Access type":
.. image:: images/aws_s3/09_user_name.png
:alt: Choose User Name and Access Type
During the next step, permissions can be assigned to the new user. To use this
user with restic, it only needs access to the ``restic-demo`` bucket. Select
"Attach existing policies directly", which will bring up a list of pre-defined
policies below. Afterwards, click the "Create policy" button to create a custom
policy:
.. image:: images/aws_s3/10_user_pre_policy.png
:alt: Assign a Policy
A new browser window or tab will open with the policy wizard. In Amazon IAM,
policies are defined as JSON documents. For this tutorial, the "Visual editor"
will be used to generate a policy:
.. image:: images/aws_s3/11_policy_start.png
:alt: Create a New Policy
For restic to work, two permission statements must be created using the visual
policy editor. The first statement is set up as follows:
.. code::
Service: S3
Allow Actions: DeleteObject, GetObject, PutObject
Resources: arn:aws:s3:::restic-demo/*
This statement allows restic to create, read and delete objects inside the S3
bucket named ``restic-demo``. Adjust the bucket's name to the name of the
bucket you created earlier. Next, add a second statement using the "Add
additional permissions" button:
.. code::
Service: S3
Allow Actions: ListBucket, GetBucketLocation
Resource: arn:aws:s3:::restic-demo
Again, substitute ``restic-demo`` with the actual name of your bucket. Note
that, unlike before, there is no ``/*`` after the bucket name. This statement
allows restic to list the objects stored in the ``restic-demo`` bucket and to
query the bucket's region.
Continue to the next step by clicking the "Review policy" button and enter a
name and description for this policy. For this tutorial, the policy will be
named ``restic-demo-policy``. Click "Create policy" to finish the process:
.. image:: images/aws_s3/13_policy_review.png
:alt: Policy Review
Go back to the browser window or tab where you were previously creating the new
user. Click the button labeled "Refresh" above the list of policies to make
sure the newly created policy is available to you. Afterwards, use the search
function to search for the ``restic-demo-policy``. Select this policy using the
checkbox on the left. Then, continue to the next step.
.. image:: images/aws_s3/14_user_attach_policy.png
:alt: Attach Policy to User
The next page will present an overview of the user account that is about to be
created. If everything looks good, click "Create user" to complete the process:
.. image:: images/aws_s3/15_user_review.png
:alt: User Creation Review
After the user has been created, its access credentials will be displayed. They
consist of the "Access key ID" (think user name), and the "Secret access key"
(think password). Copy these down to a safe place.
.. image:: images/aws_s3/16_user_created.png
:alt: User Credentials
You have now completed the configuration in AWS. Feel free to close your web
browser now.
Initializing the restic repository
==================================
Open a terminal and make sure you have the ``restic`` binary ready. First, choose
a password to encrypt your backups with. In this tutorial, ``apg`` is used for
this purpose:
.. code-block:: console
$ apg -a 1 -m 32 -n 1 -M NCL
I9n7G7G0ZpDWA3GOcJbIuwQCGvGUBkU5
Note this password somewhere safe along with your AWS credentials. Next, the
configuration of restic will be placed into environment variables. This will
include sensitive information, such as your AWS secret and repository password.
Therefore, make sure the next commands **do not** end up in your shell's
history file. Adjust the contents of the environment variables to fit your
bucket's name and your user's API credentials.
.. code-block:: console
$ unset HISTFILE
$ export RESTIC_REPOSITORY="s3:https://s3.amazonaws.com/restic-demo"
$ export AWS_ACCESS_KEY_ID="AKIAJAJSLTZCAZ4SRI5Q"
$ export AWS_SECRET_ACCESS_KEY="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"
$ export RESTIC_PASSWORD="I9n7G7G0ZpDWA3GOcJbIuwQCGvGUBkU5"
After the environment is set up, restic may be called to initialize the
repository:
.. code-block:: console
$ ./restic init
created restic backend b5c661a86a at s3:https://s3.amazonaws.com/restic-demo
Please note that knowledge of your password is required to access
the repository. Losing your password means that your data is
irrecoverably lost.
restic is now ready to be used with Amazon S3. Try to create a backup:
.. code-block:: console
$ dd if=/dev/urandom bs=1M count=10 of=test.bin
10+0 records in
10+0 records out
10485760 bytes (10 MB, 10 MiB) copied, 0,0891322 s, 118 MB/s
$ ./restic backup test.bin
scan [/home/philip/restic-demo/test.bin]
scanned 0 directories, 1 files in 0:00
[0:04] 100.00% 2.500 MiB/s 10.000 MiB / 10.000 MiB 1 / 1 items ... ETA 0:00
duration: 0:04, 2.47MiB/s
snapshot 10fdbace saved
$ ./restic snapshots
ID Date Host Tags Directory
----------------------------------------------------------------------
10fdbace 2017-03-26 16:41:50 blackbox /home/philip/restic-demo/test.bin
A snapshot was created and stored in the S3 bucket. By default backups to Amazon S3 will use the ``STANDARD`` storage class. Available storage classes include ``STANDARD``, ``STANDARD_IA``, ``ONEZONE_IA``, ``INTELLIGENT_TIERING``, and ``REDUCED_REDUNDANCY``. A different storage class could have been specified in the above command by using ``-o`` or ``--option``:
.. code-block:: console
$ ./restic backup -o s3.storage-class=REDUCED_REDUNDANCY test.bin
This snapshot may now be restored:
.. code-block:: console
$ mkdir restore
$ ./restic restore 10fdbace --target restore
restoring to restore
$ ls restore/
test.bin
The snapshot was successfully restored. This concludes the tutorial.
*****************************************************
Backing up your system without running restic as root
*****************************************************
Motivation
==========
Creating a complete backup of a machine requires a privileged process
that is able to read all files. On UNIX-like systems this is
traditionally the ``root`` user. Processes running as root have
superpower. They cannot only read all files but do also have the power
to modify the system in any possible way.
With great power comes great responsibility. If a process running as
root malfunctions, is exploited, or simply configured in a wrong way it
can cause any possible damage to the system. This means you only want
to run programs as root that you trust completely. And even if you
trust a program, it is good and common practice to run it with the
least possible privileges.
Capabilities on Linux
=====================
Fortunately, Linux has functionality to divide root's power into
single separate *capabilities*. You can remove these from a process
running as root to restrict it. And you can add capabilities to a
process running as a normal user, which is what we are going to do.
Full backup without root
========================
To be able to completely backup a system, restic has to read all the
files. Luckily Linux knows a capability that allows precisely this. We
can assign this single capability to restic and then run it as an
unprivileged user.
First we create a new user called ``restic`` that is going to create
the backups:
.. code-block:: console
root@a3e580b6369d:/# useradd --system --create-home --shell /sbin/nologin restic
Then we download and install the restic binary into the user's home
directory (please adjust the URL to refer to the latest restic version).
.. code-block:: console
root@a3e580b6369d:/# mkdir ~restic/bin
root@a3e580b6369d:/# curl -L https://github.com/restic/restic/releases/download/v0.12.1/restic_0.12.1_linux_amd64.bz2 | bunzip2 > ~restic/bin/restic
Before we assign any special capability to the restic binary we
restrict its permissions so that only root and the newly created
restic user can execute it. Otherwise another - possibly untrusted -
user could misuse the privileged restic binary to circumvent file
access controls.
.. code-block:: console
root@a3e580b6369d:/# chown root:restic ~restic/bin/restic
root@a3e580b6369d:/# chmod 750 ~restic/bin/restic
Finally we can use ``setcap`` to add an extended attribute to the
restic binary. On every execution the system will read the extended
attribute, interpret it and assign capabilities accordingly.
.. code-block:: console
root@a3e580b6369d:/# setcap cap_dac_read_search=+ep ~restic/bin/restic
.. important:: The capabilities of the ``setcap`` command only applies to this
specific copy of the restic binary. If you run ``restic self-update`` or
in any other way replace or update the binary, the capabilities you added
above will not be in effect for the new binary. To mitigate this, simply
run the ``setcap`` command again, to make sure that the new binary has the
same and intended capabilities.
From now on the user ``restic`` can run restic to backup the whole
system.
.. code-block:: console
root@a3e580b6369d:/# sudo -u restic /home/restic/bin/restic --exclude={/dev,/media,/mnt,/proc,/run,/sys,/tmp,/var/tmp} -r /tmp backup /