Why is my /tmp partition deleted or empty?
One common reason this might happen is the existence of a tmpwatch cronjob. You can check for the existence of a tmpwatch cronjob by running the following command via SSH as the root user:
crontab -l | grep tmpwatch
tmpwatch crons can be problematic since they can delete PHP-FPM private directories and other vital data stored in /tmp. If websites use PHP-FPM, this can disrupt uploads and other functions that depend on session data.
If you need to use tmpwatch, we recommend configuring the cron so that the PHP-FPM private directories are ignored. This can be done with appending the "-d" flag to the cron. For more information on configuring tmpwatch, you can reference the manual.