Linux du and df command - Key Differences

Let’s explore the differences between the df and du commands in Linux, as they both play crucial roles in managing disk space. These commands may seem similar, but they serve distinct purposes that are important to understand. Let’s break it down:

df command

df Command (Disk Free): The “df” command, short for “disk free”, provides details on the disk space usage of a file system. It provided File System, type, total size, usage, available and mount points.

Below is an example. Here -h is used for human-readable format. Notice, the counters are in K (KB), M (MB) or G (GB) etc.

Note, df command provides these details irrespective of location fromt it’s being executed. In below example, df command is run from user home location.

rakesh@jumpserver:~$ pwd
/home/rakesh
rakesh@jumpserver:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           1.2G  1.9M  1.2G   1% /run
/dev/sda3        98G   78G   15G  85% /            
tmpfs           5.9G     0  5.9G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           5.9G     0  5.9G   0% /run/qemu
/dev/sda2       512M  5.3M  507M   2% /boot/efi    
tmpfs           1.2G  144K  1.2G   1% /run/user/1000
rakesh@jumpserver:~$

Use “-T” option for filesystem type.

rakesh@jumpserver:~$ df -hT
Filesystem     Type   Size  Used Avail Use% Mounted on
tmpfs          tmpfs  1.2G  1.9M  1.2G   1% /run
/dev/sda3      ext4    98G   78G   15G  85% /
tmpfs          tmpfs  5.9G     0  5.9G   0% /dev/shm
tmpfs          tmpfs  5.0M     0  5.0M   0% /run/lock
tmpfs          tmpfs  5.9G     0  5.9G   0% /run/qemu
/dev/sda2      vfat   512M  5.3M  507M   2% /boot/efi
tmpfs          tmpfs  1.2G  144K  1.2G   1% /run/user/1000
rakesh@jumpserver:~$

You can also check specifically for a particular filesystem.

rakesh@jumpserver:~$ df -h /dev/sda2
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2       512M  5.3M  507M   2% /boot/efi
rakesh@jumpserver:~$

To check Inode information, use -i option.

rakesh@jumpserver:~$ df -i /
Filesystem      Inodes  IUsed   IFree IUse% Mounted on
/dev/sda3      6520832 363467 6157365    6% /
rakesh@jumpserver:~$

Overall, df command give you high level view of disk.

du command

du command – short for “disk usage” – a valuable tool for managing individual files and directories. It displays the amount of disk space used by a designated file or directory, along with its subdirectories.

Note, du command unlike df command give results based on current working directory, unless specific path is provided.

Here are various options.

-h : human-readable format
-s : summarize
-a : Also includes files, not just directories
–max-depth=N : print the total for a directory. max-depth=0 is equivalent to the to -s (summarize)
–exclude : exclude files that match PATTERN

Now let’s look for output using these options.

rakesh@jumpserver:/home$ pwd
/home
rakesh@jumpserver:/home$ sudo du -sh          < sudo is required if user not having permissions for all files/directories.
25G     .                      << This is total size of directory.
rakesh@jumpserver:/home$ 

rakesh@jumpserver:/home$ sudo du -h --max-depth=0       << equivalent to -s
25G     .
rakesh@jumpserver:/home$

To check usage of the sub-folders. you can use -a option if there are some files in current directory and you want size of those also listed.

rakesh@jumpserver:/home$ sudo du -h --max-depth=1
5.4G    ./admin
12M     ./admin1
20G     ./rakesh
25G     .              <<<<< This is total
rakesh@jumpserver:/home$

You can pipe the output to “sort -h” command to have output listed in order of ascending sizes.