Making sure that a system is not running out of space is very important. A lack of disk space for the basic paths such as/var/spool, or /tmp might cause unexpected results throughout the entire system, such as applications failing due to not being able to write temporary files or local e-mail not being delivered due to lack of disk space. Quotas that are not properly set up for home directories might also cause disk space to run out in a few minutes under certain circumstances.

Nagios can monitor storage space and warn administrators before such problems happen. It is also possible to monitor remote shares on other disks without mounting them. This would be useful for easily monitoring disk space on Windows boxes, without installing the dedicated Windows Nagios tools described in Chapter 10, Advanced Monitoring.