When adding fail2ban to a server with a lot of sites and enabling all jails the client got this error during the enabling process. Half the sites wouldn’t monitor.
2024-02-18 17:01:32,168 fail2ban.filterpyinotify[1111498]: ERROR add_watch: cannot watch /var/www/vhosts/system/domainname.com/logs WD=-1, Errno=No space left on device (ENOSPC)
Contrary to the error message. This server had lots of free space and plenty of iNodes. This was a watch problem.
Run this command;
cat /proc/sys/fs/inotify/max_user_watches
If it is lower than the amount of watches you are adding then this is the cause. You can try this command.
echo 20000 | tee -a /proc/sys/fs/inotify/max_user_watches
I have not yet had chance to test this on the clients server. This is documentation for the future when testing is possible.
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