I call df, or disk free, the misunderstood command because new Linux users often expect it to tell the sizes of directories and files. But it doesn’t do that– it’s for displaying useful information on filesystems. When you invoke it with no arguments, it shows free and used space on all mounted filesystems, their partitions, and mountpoints:
$ df Filesystem 1K-blocks Used Available Use% Mounted on /dev/sdb1 29222392 19353412 8404256 70% / udev 1982916 4 1982912 1% /dev tmpfs 809892 1072 808820 1% /run none 5120 0 5120 0% /run/lock none 2024724 1388 2023336 1% /run/shm /dev/sdb3 593262544 200333868 363234532 36% /home/carla/moarstuff /dev/sda1 1730404792 1616359192 27442000 99% /home/carla/storage /dev/sda2 221176480 160279584 49824796 77% /home/carla/1home
Firecracker the dog is fascinated by Linux filesystems
Add the -h switch for human-readable format, and get rid of the virtual filesystems that exist only in memory, and display just the partitions on your hard drives with grep:
$ df -h |grep ^/ /dev/sdb1 28G 19G 8.1G 70% / /dev/sdb3 566G 192G 347G 36% /home/carla/moarstuff /dev/sda1 1.7T 1.6T 27G 99% /home/carla/storage /dev/sda2 211G 153G 48G 77% /home/carla/1home
df does not operate on individual files or directories, but only filesystems. If you give it a file or directory name as an argument, it gives information for the filesystem the file is on:
$ df -h /var Filesystem Size Used Avail Use% Mounted on /dev/sdb1 28G 19G 8.1G 70% /
I like it for quickly finding out which partitions files are on. It identifies the filesystem types with the -T option:
$ df -Th |grep ^/ /dev/sdb1 ext4 28G 19G 8.1G 70% / /dev/sdb3 ext3 566G 192G 347G 36% /home/carla/moarstuff /dev/sda1 btrfs 1.7T 1.6T 27G 99% /home/carla/storage /dev/sda2 ext4 211G 153G 48G 77% /home/carla/1home
And you can hunt down specific filesystem types:
$ df -ht btrfs /dev/sda1 btrfs 1.7T 1.6T 27G 99% /home/carla/storage
Consult man df and man grep to learn more about what these excellent commands can do. Both are non-destructive commands that only read information, so you can experiment safely.
