I'm on Debian 11, trying to troubleshoot an installation of Mailman 3.3.3 that was done by someone else.
Mailman is running as a non-privileged (non-root) user called 'xyz'. On the day that Mailman was installed, that non-privileged 'xyz' user was able to execute mailman commands successfully to create, view and modify lists.
A couple of days later, when the 'xyz' user tried running those same mailman commands, they failed with this error: PermissionError: [Errno 13] Permission denied: '/var/log/mailman3/mailman.log'
Doing "ls -l" on the file /var/log/mailman3/mailman.log showed this: -rw-r----- 1 list list 0 Jan 6 00:00 /var/log/mailman3/mailman.log
When I did a 'ps' command, I saw that all of the mailman processes are running as user 'xyz'. No processes were running as the user 'list'.
It seems that some process is rotating the mailman.log file at midnight, and the newly-created mailman.log is being owned by user 'list'.
Can anyone explain why this is happening, and how to fix it?