Linux

Docker Volume Backup?

As I'm not using a Swarm or cluster, I consider Docker volumes volatile and use mounts where I need persistence. All my configuration and other persistent data is under /opt/docker/<container>/<foldername>. And /opt/docker gets backed up regularly using restic.

./ bind mount everything in your compose file because dockers volume storage is bloody annoying to backup. Then you can just back up the one folder with everything in it.

Backup for docker is no different than backing up anything else.

Volumes are located in /var/lib/docker/volumes by default, so just back up that directory with Restic or Borg, or something like Backrest if you want notifications and stuff handled for you.

Or you can do mount points to a directory instead of using volumes and back that up, but it's really the same process.

I just bind mount volumes I want to keep and use duplicati to backup the contents of my containers folder. Another idea if you are committed to docker volumes, is to also mount them to your backup solution.

I made my own solution since I wasn't impressed by projects I had found. There's two parts, the backup image and the restore image.

I use it like so:

services:
  restore_sabnzbd:
    image: untouchedwagons/simple-restore:1.0.5
    container_name: restore_sabnzbd
    restart: no
    environment:
      - BACKUP_APPEND_DIRECTORY=/docker/production/sabnzbd
      - BACKUP_BASE_NAME=sabnzbd
      - FORCE_OWNERSHIP=1000:1000
    volumes:
      - sabnzbd:/data
      - /mnt/tank/Media/Backups:/backups

  sabnzbd:
    image: ghcr.io/onedr0p/sabnzbd:4
    container_name: sabnzbd
    restart: unless-stopped
    user: 1000:1000
    volumes:
      - sabnzbd:/config
      - /mnt/tank/Media/Usenet:/mnt/data/Usenet
    depends_on:
      restore_sabnzbd:
        condition: service_completed_successfully
    networks:
      - traefik_default

  backup_sabnzbd:
    image: untouchedwagons/simple-backup:1.1.0
    container_name: backup_sabnzbd
    restart: unless-stopped
    environment:
      TZ: "America/Toronto"
      BACKUP_APPEND_DIRECTORY: "/docker/production/sabnzbd"
      BACKUP_BASE_NAME: "sabnzbd"
      BACKUP_RETENTION: "24"
      BACKUP_FREQUENCY: "0 0 * * *"
    volumes:
      - sabnzbd:/data:ro
      - /mnt/tank/Media/Backups:/backups
      
networks:
  traefik_default:
    external: true

volumes:
  sabnzbd:

The restore container looks for a file called RESTORED in /data and if one isn't found it'll try to restore the latest backup (if available) and then create a RESTORED file. The backup container ignores this file during backup.

I made an ansible role for this:

https://github.com/CSUN-CCDC/ccdc-2024/tree/main/linux/ansible/roles/docker

It was designed for a cybersecurity competition, and can back up containers and volumes. The volume back up works by creating another container and then mounting the volume to that container, and within that container a simple tar backup is ran.

I don’t have an answer for this, but I wonder if something for this could be set up with a docker container. I know LinuxServer.io has a really good image system where you can run a container with “mods”. For example, you might be able to run their base Ubuntu / Fedora / Alpine image and then customizing it to run your script as a service / cron job / systemd service.

https://hub.docker.com/r/lsiobase/ubuntu

https://docs.linuxserver.io/general/container-customization/

This is a classic conundrum.

Containers and their volumes are supposed to be ephemeral (right?).

Yet we use them to run little apps where we configure settings etc in the app which we would like to “keep” - thus back up. Yes in a proper set up you would hook your container up to something that is not ephemeral like a database somewhere, but often we just want an app, see it’s got a self contained docker image, and just run it.

Whilst not in the spirit of things… I’ve tried using Borg backup however it just fails due to random permissions on the volumes.

I should spend more time looking into it but haven’t the time right now, could be the solution is specific to the app/container but the simplicity of just backing up a /volumes/* directory is soooo tempting…

Edit upon reflection, what about a sudo cron tab to zip volumes and set useful permissions on the zip. Then Borg to backup the zip. Borg (or at least vorta) can easily run scripts before/after and pass variables relating to the backup though.

Biggest issue I've encountered a couple times is some applications like Gitlab etc it's much better to use the backup process they provide than to try with disk copies etc. Although I haven't tried to use a btrfs send but rsync / cp / tar etc all seem to fail with the special files and extended fs attributes.

I implemented Duplicati as a fast, easy and adaptable backup solution at my workplace. It's itself running as a docker stack on every node in the swarm. Even migration to new servers is possible, because it can restore file permissions and ownership too. Just give it access to either the volumes path of the host or just the whole host file system.

Can be accessed via web interface, password protected. I actually recommend the image by the linuxserver community instead of the "official" for a simple, no-config deployment that starts up in seconds. Just add a data volume and your host bind in your compose file and that's pretty much it.