To test local resources such as hard drive capacity, the load on the swap area, the current CPU load, or whether a specific process is running, various local plugins are available. They are called "local" because they have to be installed on the computer that is to be checked.
The Nagios server has no way to directly access such information over the network, without taking further measures. However, it can start local plugins on the remote host via a remote shell (Figure 5-1, page 100, Client 2). Only the Secure Shell, SSH, should be considered for use here; the Remote Shell, RSH, simply has too many security holes.
To do this, the Nagios server runs the program
check_by_ssh, which is given ...