In order to restart a service on your dedicated machine, follow these steps:

Log in your WHM control panel

Search for the Restart Services option.

Under the specified section you can find all services available on the machine that can be restarted. The standard list of the services is:

DNS Server (Bind/NSD)
FTP Server
HTTP Server (Apache)
IMAP Server
Mail Server (Exim)
POP3 Server
SQL Server
SSH Server