Rebooting a server should be avoided if at all possible, although sometimes it’s essential. However if it fails to come back online there are a number of possible problems:

Server is back online but can’t establish SSH connection:
Try pinging the server using the command

ping [ip address]

Using this command from an MS-DOS/Windows Command Prompt will attempt to ping the server four times, however if this is done from a linux terminal it will ping until you hit CTRL+C to stop it.

If you cannot ping the server then the probability is that it has failed to restart, there was a problem loading the OS kernel or there is a problem with the eth0 or eth1 settings. In this case you have no choice but to contact your provider’s support department.

If you can ping the server try establishing a connection using Telnet, or if you can access WHM/cPanel try establishing an SSH connection through this.

Server is back online but no apache, mail or anything else apart from SSH working!
Try typing the command:

service iptables stop

This is especially relevent if using cPanel as cPanel uses ports 2082 and 2086 for admin, ports which the iptables service blocks.

I can access WHM but none of my website work!
Try restarting apache. You can do this by logging in the WHM and choosing ‘restart services’ or by using the command

httpd restart

at the command prompt. If you get a command similar to ‘httpd is not running’ then this means apache is not running. Typing ‘httpd’ will start Apache. This is probaby a better way to restart apache as any error messages displayed would not be displayed in WHM