The df command reports the system's disk space usage. If you type the command df at a shell prompt, the output looks similar to the following:
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/hda2             10325716   2902060   6899140  30% /
/dev/hda1                15554      8656      6095  59% /boot
/dev/hda3             20722644   2664256  17005732  14% /home

By default, this utility shows the partition size in 1 kilobyte blocks and the amount of used and available disk space in kilobytes. To view the information in megabytes and gigabytes, use the command df -h. The -h argument stands for human-readable format. The output looks similar to the following:
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda2             9.8G  2.8G  6.5G  30% /
/dev/hda1              15M  8.5M  5.9M  59% /boot
/dev/hda3              20G  2.6G   16G  14% /home

To view the system's disk space usage in a graphical format, use the Filesystems tab in the GNOME System Monitor. To start it on the GNOME desktop, go to the Main Menu Button (on the Panel) => Programs => System => System Monitor or type gtop at a shell prompt from within any X Window System desktop. Then choose the Filesystems tab.

Figure 20-3. GNOME System Monitor

The du command displays the estimated amount of space being used by files in a directory. If you type du at a shell prompt, the disk usage for each of the subdirectories will be displayed in a list. The grand total for the current directory and subdirectories will also be shown, as the last line in the list. If you do not want to see all the subdirectories, use the command du -hs to see only the grand total for the directory in human-readable format. Use the du --help command to see more options.

Monitoring Filesystems

Red Hat Linux provides a utility called diskcheck that monitors the amount of free disk space on the system. Based on the configuration file, it will send email to the system administrator when one or more disk drives reach a specified capacity.

This utility is run as an hourly cron [1] task.

The following variables can be defined in /etc/diskcheck.conf:

You do not have to restart a service if you change the configuration file because it is read each time the cron task is run.



Refer to Chapter 22 for more information on cron.