Reboots are sometimes necessary and always slightly risky.
WHEN A REBOOT IS NEEDED
After a kernel update, for the new kernel to take effect After certain library updates affecting running processes When a system is in a state that cannot be resolved otherwise
BEFORE REBOOTING
Confirm every service is enabled to start at boot. A service running but not enabled disappears after a reboot, which is a confusing and common failure. Take a snapshot if the system state is uncertain. Choose a quiet time. Know how to reach the console if it does not come back.
AFTER REBOOTING
Confirm every expected service is running Test the website Test mail, if the server handles it Check cron jobs ran as expected Check mounted filesystems are mounted
THE CLASSIC FAILURE
A service configured manually months ago, running happily, never enabled at boot. The reboot reveals it, usually at the worst moment.
Check systemctl is-enabled for each important service now rather than finding out later.
