Is there a historical log kept of all the backups that have taken place?
Yes, but that will be rotated.
Currently, the backup server creates a task log entry for every backup – you can easily search them by going to
Administration -> Tasks, there you can enable a filter for the "backup" task type.
Those logs are saved in
/var/log/pve/tasks
, with two characters from the UPID's
pstart
(process start time, the third field of a
UPID:<node>:<pid>:<pstart>:<task-id>:<start-time>:<worker-type>:<worker-id>:<username>
task ID) as directory-index to avoid having to many files in a single directory.
For those the following retention is happening:
There are
archive
files that act as an index of (finished) task entries, as long as a task log is referenced by one of those it's kept, otherwise it will get removed.
The archive logs are rotated, by a default mechanism of "rotate if bigger than 512 KiB in size" and if such a rotation happens only the newest 20 archive-files will be kept – this amounts to roughly 100'000 task entries that are saved.
But, you can also override this behavior by setting a
task-log-max-days
from the Proxmox Backup Server's
node.cfg
, if that's set then the archive's will be searched and only those will be removed that contain tasks that are older than the
now - max-days
cut-off.
You can set that config using
proxmox-backup-manager node update --task-log-max-days 365
(here ensuring that all task that started in the last 365 days will be kept).
Additionally, Proxmox VE uploads the client task-log from a backup also to the backup server, but that's saved within the backup snapshot itself, so if that's removed by a user that log is also gone, so probably not useful for your audit purpose.