Tar errors like "file has changed" in backing up /var/lib/incus?

Incus
1

The backup documentation at How to back up an Incus server - Incus documentation states that best practices is to do a full tar backup of /var/lib/incus.

In writing a script for full backups for offline storage I noticed that tar of /var/lib/incus always gives tar errors of files changing and not backing up sockets

E.g.

tar: /var/lib/incus/storage-pools/default/containers/REDACTED/rootfs/...gitaly.socket: socket ignored
tar: /var/lib/incus/storage-pools/default/containers/REDACTED...application_json.log: file changed as we read it
tar: /var/lib/incus/storage-pools/default/containers/REDACTED/rootfs/var/log/journal/e9f2d59209754628872cc6607f82ca4e/system.journal: file changed as we read it
tar: /var/lib/incus/storage-pools/default/containers/REDACTED/rootfs/var/spool/postfix/private/scache: socket ignored

How ok are those to ignore? Is it best practice to stop or pause containers (or incus) on that incus server while doing the full backup of /var/lib/incus?

2

Sockets are fine to ignore, the files changed are a bit more problematic in general, though from the output above, I’d suspect it may be fine.

That’s why --optimized-storage exists as when that’s passed and the storage driver supports it, you end up with a binary backup instead, coming directly from the storage driver which is guaranteed to be consistent even if changes were happening to the instance during backup. (They also tend to be smaller in size and faster to restore which is a nice bonus).