Both Linux and UNIX-like systems offers two commands for checking out free disk space:
(a) df command : Report file system disk space usage.
(b) du command : Estimate file space usage.
df command examples - to check free disk space
Type df -h or df -k to list free disk space:
$ df -h
$ df -k
Filesystem Size Used Avail Use% Mounted on /dev/sdb1 20G 9.2G 9.6G 49% / varrun 393M 144k 393M 1% /var/run varlock 393M 0 393M 0% /var/lock procbususb 393M 123k 393M 1% /proc/bus/usb udev 393M 123k 393M 1% /dev devshm 393M 0 393M 0% /dev/shm lrm 393M 35M 359M 9% /lib/modules/2.6.20-15-generic/volatile /dev/sdb5 29G 5.4G 22G 20% /media/docs /dev/sdb3 30G 5.9G 23G 21% /media/isomp3s /dev/sda1 8.5G 4.3G 4.3G 51% /media/xp1 /dev/sda2 12G 6.5G 5.2G 56% /media/xp2 /dev/sdc1 40G 3.1G 35G 9% /media/backup
The df utility displays statistics about the amount of free disk space on the specified file system or on the file system of which file is a part. Values are displayed in 512-byte per block counts. -H option is called as "Human-readable" output. It use unit suffixes: Byte, Kilobyte, Megabyte, Gigabyte, Terabyte and Petabyte in order to reduce the number of digits to four or fewer using base 10 for sizes i.e. you see 30G (30 Gigabyte).
du command examples
du shows how much space one ore more files or directories is using, enter:
$ du -sh
The -s option summarize the space a directory is using and -h option provides "Human-readable" output.
Above programs are good if GUI is not installed or you are working with remote system over the ssh based session. Linux and UNIX-like oses comes with KDE and Gnome desktop system. You will find Free Disk Space Applet located under GUI menus. Here is a sample from Fedora Linux version 22 system: