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 none 256796 0 256796 0% /dev/shm
By default, df 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 -h option with the df command. The -h option stands for human-readable format. The output for the df -h command 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 none 251M 0 250M 0% /dev/shm
In the list of partitions (the Mounted on column), you can see an entry for /dev/shm. This entry represents the system's virtual memory file system.
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 the totals for 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.
To view the system's partitions and disk space usage in a graphical format, use the System Monitor tab (as shown at the bottom of Figure 25-2).