Usecase

Main Goal:_ Create Borg Backups of a set of docker volumes. Nothing more (for now). Backups should be done on a snapshotted, or equivalent environment.

Prerequisites

1. Storage (where Docker files reside, /var/lib/docker):
   1. Highly recommend: a FS that can shapshot. (btrfs/zfs)
   2. Second option: a FS that can create reflinks (XFS)
   3. Third option: keep an rsync clone for backup. Not reccomended. 2x space usage.
2. A Docker container with --privileged access (we need to run docker inside)
3. An overview of the volumes to be in the backup
4. An exclusion list (Per volume?)
5. A backup schedule & options (borgmatic Yaml files?)

Thoughts

• How to restore in a most convenient way?
• Can/should we use native borgmatic Database Backup options?
• Nice one: Get usage identical to Standard Borgmatic Container (With Cron support)

Whole process - summary

• Container takes the whole Borgmatic Docker config, and thus aims to be an in-place addition to Borgmatic Container (Exception: --privileged flag).

• All the config mappings, except for the Cron wil be duplicated to the borgmatc container.

• At backup time:

  • Optionally stop running containers
  • All the subvolumes in the /var/lib/docker location will be snapshotted.
  • Optionally start stopped containers
  • The container registrations under the snapshotted /var/lib/docker will be removed (to prevent container start).
  • Nested Docker daemon will be started
  • Borgmatic docker container will be started with all volumes attached.
  • After backup, cleanup:
    • Nested Docker Daemon will be stopped
    • All snapshots under /var/lib/docker will be removed
    • Sleep until next backup event.

• All the (snapshotted) containers will be mounted under /mnt/volumes, under their own name.

Backup Preparation process

1. Start a privileged container with options:
   1. bind-mount to host's /var/lib/docker path
   2. BTRFS tools installed
   3. Docker and tools installed

Snapshot Options