You might run into a situation where a specific service or a command fails with similar error messages:
/scripts/restartsrv_httpd --start [...............] Mar 11 00:07:13 server.domain.com systemd: Failed to set a watch for httpd.service's PID file /run/apache2/httpd.pid: No space left on device
tail -fn0 /var/log/messages tail: inotify resources exhausted tail: inotify cannot be used, reverting to polling
This suggets that the server is running out of Inotify watches. For more information about Inotify watches and how to count them per PID you can refer to the following article:
How to find what has the most inotify registered watches
In these situations you can temporarily increase the fs.inotify.max_user_watches system limit to some number bigger than the number of used Inotify watches on the server so you are able to start a service or run a specific command. The following command should help with that:
For a more permanent resolution, to this issue you need to reach out to your hosting provider or a system administrator.