check_apt: Checks for
aptsoftware updates. The main advantage over
cron-aptis that you can centralize your package monitoring: easier to refer to, and more obvious if a machine is missing.
check_jabber: The most useful aspect of this is the
-Doption, which warns when your jabber server certificate is close to expiring. Command-line options mean you can fine-tune what you send to the server and what you expect back.
check_mysql: By default this will check the local database anonymously. You can specify username, hostname, and so on, but be warned: Any password will be sent clear-text! A very useful feature is the ability to check whether the slave server is keeping up with the master server.
- check_krb5 (homepage): Keep tabs on your Kerberos server. The plugin takes hostname, realm, principal and keytab options, so is appropriately secure.
- check_ldap: Will check ldaps as well as ldap, but you do have to provide a login ID and password in plaintext, or just check anonymous bind.
More generally: Roll your own quickly with check_generic (homepage). This lets you define a command and a set of expectations/thresholds for the return data, thus saving you much of the work involved in writing a plugin. The homepage has thorough documentation and examples.