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98 lines
3.9 KiB
Markdown
98 lines
3.9 KiB
Markdown
---
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title: Run custom commands during the backup lifecycle
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layout: default
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nav_order: 5
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parent: How Tos
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---
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# Run custom commands during the backup lifecycle
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In certain scenarios it can be required to run specific commands before and after a backup is taken (e.g. dumping a database).
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When mounting the Docker socket into the `docker-volume-backup` container, you can define pre- and post-commands that will be run in the context of the target container (it is also possible to run commands inside the `docker-volume-backup` container itself using this feature).
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Such commands are defined by specifying the command in a `docker-volume-backup.[step]-[pre|post]` label where `step` can be any of the following phases of a backup lifecycle:
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- `archive` (the tar archive is created)
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- `process` (the tar archive is processed, e.g. encrypted - optional)
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- `copy` (the tar archive is copied to all configured storages)
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- `prune` (existing backups are pruned based on the defined ruleset - optional)
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{: .note }
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So that the `docker-volume-backup` container can access the labels on other containers, it is necessary that the docker socket is mounted into
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the `docker-volume-backup` container as shown in the Quickstart example.
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Taking a database dump using `mysqldump` would look like this:
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```yml
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version: '3'
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services:
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# ... define other services using the `data` volume here
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database:
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image: mariadb
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volumes:
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- backup_data:/tmp/backups
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labels:
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- docker-volume-backup.archive-pre=/bin/sh -c 'mysqldump --all-databases > /backups/dump.sql'
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volumes:
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backup_data:
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```
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{: .note }
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Due to Docker limitations, you currently cannot use any kind of redirection in these commands unless you pass the command to `/bin/sh -c` or similar.
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I.e. instead of using `echo "ok" > ok.txt` you will need to use `/bin/sh -c 'echo "ok" > ok.txt'`.
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If you have more than one `docker-volume-backup` container (possibly across several docker-compose environments) to backup or you are using
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multiple backup schedules, you will need to use `EXEC_LABEL` in the configuration and a `docker-volume-backup.exec-label` label on each
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container using custom commands to ensure that the commands are only run by the correct `docker-volume-backup` instance.
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{: .important }
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In case you use `EXEC_LABEL` together with configuration mounted from `conf.d` it's important to understand that a distinct `EXEC_LABEL` __should be set in each configuration__.
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Else, schedules that do not specify an `EXEC_LABEL` will still trigger commands on all containers with such labels, no matter whether they specify `docker-volume-backup.exec-label` or not.
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```yml
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version: '3'
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services:
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database:
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image: mariadb
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volumes:
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- backup_data:/tmp/backups
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labels:
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- docker-volume-backup.archive-pre=/bin/sh -c 'mysqldump --all-databases > /tmp/volume/dump.sql'
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- docker-volume-backup.exec-label=database
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backup:
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image: offen/docker-volume-backup:v2
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environment:
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EXEC_LABEL: database
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volumes:
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- data:/backup/dump:ro
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- /var/run/docker.sock:/var/run/docker.sock:ro
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volumes:
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backup_data:
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```
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The backup procedure is guaranteed to wait for all `pre` or `post` commands to finish before proceeding.
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However, there are no guarantees about the order in which they are run, which could also happen concurrently.
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By default the backup command is executed by the user provided by the container's image.
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It is possible to specify a custom user that is used to run commands in dedicated labels with the format `docker-volume-backup.[step]-[pre|post].user`:
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```yml
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version: '3'
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services:
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gitea:
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image: gitea/gitea
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volumes:
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- backup_data:/tmp
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labels:
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- docker-volume-backup.archive-pre.user=git
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- docker-volume-backup.archive-pre=/bin/bash -c 'cd /tmp; /usr/local/bin/gitea dump -c /data/gitea/conf/app.ini -R -f dump.zip'
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```
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Make sure the user exists and is present in `passwd` inside the target container.
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