Restic: restic / prune doesn't consider hostname

[DerRockWolf]

The readme currently states the following:

When using restic, at least one of HOSTNAME or BACKUP_NAME must be unique, when sharing a repository.
Otherwise other instances using the same repository might prune your backups prematurely.

But the restic forget call currently doesn't consider the hostname, as the --host parameter is missing:

docker-mc-backup/scripts/opt/backup-loop.sh

Line 406 in a5addf5

command restic --retry-lock "${RESTIC_RETRY_LOCK}" forget --tag "${restic_tags_filter}" ${PRUNE_RESTIC_RETENTION} "${@}"

So if you have multiple different servers that are backed up into one restic repository, the mc-backup container of the first server could delete snapshots of the second server if the BACKUP_NAME isn't unique.

I've noticed this because your minecraft helm chart uses the worldSaveName as the BACKUP_NAME, which default to world and, at least in my case, was unchanged.

Depending on how we interpret it this can be solved in two ways:

• Correct the readme to explicitly state that BACKUP_NAME must be unique
• Change the restic forget call to include --host "${RESTIC_HOSTNAME}"

[itzg]

The README already says it should be unique; however, I agree that the --host probably should also be included on forget and any others to balance the backup invocation.

It also looks like the chart should be corrected to specify RESTIC_HOSTNAME with a stable value. As it is, the pod name will get picked up as the hostname, which changes on redeploys.

[DerRockWolf]

The README already says it should be unique

Is says that HOSTNAME or BACKUP_NAME must be unique, not both. In my setup only HOSTNAME (or actually RESTIC_HOSTNAME) is unique. But because of the missing --host parameter on mc-backup container can forget & prune snapshots of other servers as only --tag is passed.

I'll open PRs for both docker-mc-backup and the helm chart.

Edit:

both PRs are opened:

• feat(restic): also filter for hostname (--host) in restic forget command #248
• feat: overriding BACKUP_NAME and set RESTIC_HOSTNAME minecraft-server-charts#274

Please let me know about any concerns you have, especially regarding the breaking change in the helm chart.