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Aug 9, 2021

volume-backup

An utility to backup and restore docker volumes. For more info, read my article on Medium

Note: Make sure no container is using the volume before backup or restore, otherwise your data might be damaged. See Miscellaneous for instructions.

Note: When using docker-compose, make sure to backup and restore volume labels. See Miscellaneous for more information.

Backup

Backup to standard output

This avoids mounting a second backup volume and allows to redirect it to a file, network, etc.

Syntax:

docker run -v [volume-name]:/volume --rm --log-driver none loomchild/volume-backup backup - > [archive-name]

For example:

docker run -v some_volume:/volume --rm --log-driver none loomchild/volume-backup backup - > some_archive.tar.bz2

will archive volume named some_volume to some_archive.tar.bz2 archive file.

Note: --log-driver none option is necessary to avoid storing an entire backup in a temporary stdout JSON file. More info in Docker logging documentation and in this issue.

WARNING: This method should not be used under PowerShell on Windows as no usable backup will be generated.

Backup to a file

Syntax:

docker run -v [volume-name]:/volume -v [output-dir]:/backup --rm loomchild/volume-backup backup [archive-name]

For example:

docker run -v some_volume:/volume -v /tmp:/backup --rm loomchild/volume-backup backup some_archive

will archive volume named some_volume to /tmp/some_archive.tar.bz2 archive file.

Restore

Restore will fail if the target volume is not empty (use -f flag to override).

Restore from standard input

This avoids mounting a second backup volume.

Note: Don't forget the -i switch for interactive operation.

Syntax:

docker run -i -v [volume-name]:/volume --rm loomchild/volume-backup restore - < [archive-name]

For example:

docker run -i -v some_volume:/volume --rm loomchild/volume-backup restore - < some_archive.tar.bz2

will clean and restore volume named some_volume from some_archive.tar.bz2 archive file.

Restore from a file

Syntax:

docker run -v [volume-name]:/volume -v [output-dir]:/backup --rm loomchild/volume-backup restore [archive-name]

For example:

docker run -v some_volume:/volume -v /tmp:/backup --rm loomchild/volume-backup restore some_archive

will clean and restore volume named some_volume from /tmp/some_archive.tar.bz2 archive file.

Copy volume between hosts

One good example of how you can use the output to stdout would be directly migrating the volume to a new host

Syntax:

docker run -v [volume-name]:/volume --rm --log-driver none loomchild/volume-backup backup - |\
     ssh [receiver] docker run -i -v [volume-name]:/volume --rm loomchild/volume-backup restore -

Note: In case there are no traffic limitations between the hosts you can trade CPU time for bandwidth by turning off compression as shown in the example below.

For example:

docker run -v some_volume:/volume --rm --log-driver none loomchild/volume-backup backup -c none - |\
     ssh user@new.machine docker run -i -v some_volume:/volume --rm loomchild/volume-backup restore -c none -

Miscellaneous

  1. Upgrade / update volume-backup

    docker pull loomchild/volume-backup
    
  2. volume-backup is also available from GitHub Container Registry (ghcr.io), to avoid DockerHub usage limits:

    docker pull ghcr.io/loomchild/volume-backup
    

    Note: you'll need to write ghcr.io/loomchild/volume-backup instead of just loomchild/volume-backup when running the utility.

  3. Find all containers using a volume (to stop them before backing-up)

    docker ps -a --filter volume=[volume-name]
    
  4. Exclude some files from the backup and send the archive to stdout

    docker run -v [volume-name]:/volume --rm --log-driver none loomchild/volume-backup backup -e [excluded-glob] - > [archive-name]
    
  5. Use different compression algorithm for better performance

    docker run -v [volume-name]:/volume --rm --log-driver none loomchild/volume-backup backup -c pigz - > [archive-name]
    
  6. Show simple progress indicator using verbose -v flag (works both for backup and restore)

    docker run -v [volume-name]:/volume --rm --log-driver none loomchild/volume-backup backup -v - > [archive-name]
    
  7. Pass additional arguments to the Tar utility using -x option

    docker run -v [volume-name]:/volume --rm --log-driver none loomchild/volume-backup backup -x --verbose - > [archive-name]
    
  8. Volume labels are not backed-up or restored automatically, but they might be required for your application to work (e.g. when using docker-compose). If you need to preserve them, create a label backup file as follows: docker inspect [volume-name] -f "{{json .Labels}}" > labels.json. When restoring your data, target volume needs to be created manually with labels before launching the restore script: docker volume create --label "label1" --label "label2" [volume-name].

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docker volume backup & restore utility

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