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Merge pull request #2509 from restic/improve-check-docs

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doc: Improve check documentation
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doc/045_working_with_repos.rst
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@ -82,54 +82,85 @@ Furthermore you can group the output by the same filters (host, paths, tags):
1 snapshots 1 snapshots
Checking a repo's integrity and consistency Checking integrity and consistency
=========================================== ==================================
Imagine your repository is saved on a server that has a faulty hard Imagine your repository is saved on a server that has a faulty hard
drive, or even worse, attackers get privileged access and modify your drive, or even worse, attackers get privileged access and modify the
backup with the intention to make you restore malicious data: files in your repository with the intention to make you restore
malicious data:
.. code-block:: console .. code-block:: console
$ echo "boom" >> backup/index/d795ffa99a8ab8f8e42cec1f814df4e48b8f49129360fb57613df93739faee97 $ echo "boom" > /srv/restic-repo/index/de30f3231ca2e6a59af4aa84216dfe2ef7339c549dc11b09b84000997b139628
In order to detect these things, it is a good idea to regularly use the Trying to restore a snapshot which has been modified as shown above
``check`` command to test whether everything is alright, your precious will yield an error:
backup data is consistent and the integrity is unharmed:
.. code-block:: console
$ restic -r /srv/restic-repo --no-cache restore c23e491f --target /tmp/restore-work
...
Fatal: unable to load index de30f323: load <index/de30f3231c>: invalid data returned
In order to detect these things before they become a problem, it's a
good idea to regularly use the ``check`` command to test whether your
repository is healthy and consistent, and that your precious backup
data is unharmed. There are two types of checks that can be performed:
- Structural consistency and integrity, e.g. snapshots, trees and pack files (default)
- Integrity of the actual data that you backed up (enabled with flags, see below)
To verify the structure of the repository, issue the ``check`` command.
If the repository is damaged like in the example above, ``check`` will
detect this and yield the same error as when you tried to restore:
.. code-block:: console .. code-block:: console
$ restic -r /srv/restic-repo check $ restic -r /srv/restic-repo check
Load indexes ...
ciphertext verification failed load indexes
error: error loading index de30f323: load <index/de30f3231c>: invalid data returned
Fatal: LoadIndex returned errors
Trying to restore a snapshot which has been modified as shown above will If the repository structure is intact, restic will show that no errors were found:
yield the same error:
.. code-block:: console .. code-block:: console
$ restic -r /srv/restic-repo restore 79766175 --target /tmp/restore-work $ restic -r /src/restic-repo check
Load indexes ...
ciphertext verification failed load indexes
check all packs
check snapshots, trees and blobs
no errors were found
By default, ``check`` command does not check that repository data files By default, the ``check`` command does not verify that the actual data files
are unmodified. Use ``--read-data`` parameter to check all repository on disk in the repository are unmodified, because doing so requires reading
data files: a copy of every data file in the repository. To tell restic to also verify the
integrity of the data files in the repository, use the ``--read-data`` flag:
.. code-block:: console .. code-block:: console
$ restic -r /srv/restic-repo check --read-data $ restic -r /srv/restic-repo check --read-data
...
load indexes load indexes
check all packs check all packs
check snapshots, trees and blobs check snapshots, trees and blobs
read all data read all data
[0:00] 100.00% 3 / 3 items
duration: 0:00
no errors were found
Use the ``--read-data-subset=n/t`` parameter to check only a subset of the .. note:: Since ``--read-data`` has to download all data files in the
repository data files at a time. The parameter takes two values, ``n`` and repository, beware that it might incur higher bandwidth costs than usual
``t``. When the check command runs, all data files in the repository are and also that it takes more time than the default ``check``.
logically divided in ``t`` (roughly equal) groups, and only files that
belong to the group number ``n`` are checked. For example, the following Alternatively, use the ``--read-data-subset=n/t`` parameter to check only a
commands check all repository data files over 5 separate invocations: subset of the repository data files at a time. The parameter takes two values,
``n`` and ``t``. When the check command runs, all data files in the repository
are logically divided in ``t`` (roughly equal) groups, and only files that
belong to group number ``n`` are checked. For example, the following commands
check all repository data files over 5 separate invocations:
.. code-block:: console .. code-block:: console
@ -138,4 +169,3 @@ commands check all repository data files over 5 separate invocations:
$ restic -r /srv/restic-repo check --read-data-subset=3/5 $ restic -r /srv/restic-repo check --read-data-subset=3/5
$ restic -r /srv/restic-repo check --read-data-subset=4/5 $ restic -r /srv/restic-repo check --read-data-subset=4/5
$ restic -r /srv/restic-repo check --read-data-subset=5/5 $ restic -r /srv/restic-repo check --read-data-subset=5/5