Looking around I've found that this isn't too uncommon. The message was :

error: Compressing program wrote following message to stderr when compressing log /var/log/nginx/error.log.1:

gzip: stdout: No space left on device
error: failed to compress log /var/log/nginx/error.log.1

Following the advice from 'Fix Common problems' I'll include the Diagnostics (from before a reboot). I'll reboot after this to clear the problem for now.

tower-diagnostics-20261004-0701.zip

After a reboot df-h tells me /var/log is now back to 3,2 MB (from 128MB), i.e. 3%.

Edited Sunday at 05:16 AM1 day by RikStigter
additional info

Thanks for the diagnostics, they show the cause clearly.

Your log filesystem was filled by one nginx error repeated tens of thousands of times: the WebGUI could not find the default Docker icon (dynamix.docker.manager/images/question.png). The Dashboard requests that image for any container that doesn't have its own icon, so every Dashboard view added more errors.

Eventually there was no space left even to compress the old logs.

Your syslog also shows what started it. On Oct 2 at 05:00 the Docker auto-update installed updates for iperf3 and StirlingPDF, and StirlingPDF's icon could not be downloaded. The first missing-icon error appeared at your next Dashboard visit. This is a known bug in 7.3.2: updating or removing a container that has no icon deletes the shared default icon.

The reboot fixed it for now because it restored the icon. But it will come back the next time an icon-less container gets updated. The fix is in 7.3.3-rc.2 ("Docker Manager no longer removes the shared default icon when an icon-less container is removed or updated"). I recommend updating to it, or to 7.3.3 stable when it is released.

If it happens again after updating, please post new diagnostics before you reboot.

Thanks!

Since 7.3.3. is probably not very far away I'll wait for that release and reboot when and if neccesary.

BTW I may not have noticed this because I start the StirlingPDF docker only when I need it. Which isn't very often.