Monitoring network services

Nagios also offers plugins that monitor different network services. These include commands for checking FTP, DHCP protocol, and WWW servers. It is also possible for Nagios to monitor itself.

Checking the FTP server

Nagios allows you to verify whether an FTP server is listening for connections by using the check_ftp command. This plugin is identical to check_tcp, with the difference that the port is optional. By default, a valid FTP welcome message is expected.

check_ftp -H host [-p port] [-w <warning time>]
          [-c <critical time>] [-s <send string>]
          [-e <expect string>] [-q <quit string>] [-A] [-m <maximum bytes>] [-d <delay>]
          [-t <timeout seconds>] [-r <refuse state>] [-M <mismatch state>] [-v] [-4|-6] [-j]
          [-D <days to cert expiry>] [-S] [-E]

The port argument can be omitted and defaults to 21, or 990 for SSL-based connections. A sample command definition for...