The df command (short for disk free), is used to display information related to file systems about total space and available space.

Syntax :

df [OPTION]... [FILE]...

If no file name is given, it displays the space available on all currently mounted file systems.
For example :

df

Output :

Filesystem     1K-blocks     Used Available Use% Mounted on
udev             3996816        0   3996816   0% /dev
tmpfs             804624    10020    794604   2% /run
/dev/sda9       68117056 18036160  46597712  28% /
tmpfs            4023116    29848   3993268   1% /dev/shm
tmpfs               5120        4      5116   1% /run/lock
tmpfs            4023116        0   4023116   0% /sys/fs/cgroup
/dev/loop0         88832    88832         0 100% /snap/simplescreenrecorder/1
/dev/loop2         85888    85888         0 100% /snap/core/3748
/dev/loop3         85888    85888         0 100% /snap/core/3604
/dev/loop1         83328    83328         0 100% /snap/core/3887
/dev/sda10      78873504 67530504   7313356  91% /home
/dev/sda1         507904    30908    476996   7% /boot/efi
tmpfs             804624       12    804612   1% /run/user/121
tmpfs             804624       64    804560   1% /run/user/1000

Now, if you specify particular file, then it will show mount information of that particular file.
For example:

df /home/mandeep/test/test.cpp

Output :

Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sda10      78873504 67528220   7315640  91% /home

Options for df command :

-a, –all : includes pseudo, duplicate and inaccessible file systems.
-B, –block-size=SIZE : scales sizes by SIZE before printing them.
-h, –human-readable : print sizes in power of 1024
-H, –si: print sizes in power of 1000
-i, –inodes : list inode information instead of block usage
-l, –local : limit listing to local file systems
-P, –portability : use POSIX output format
–sync : invoke sync before getting usage info
–total : elide all entries insignificant to available space, and produce grand total
-t, –type=TYPE : limit listing to file systems of type TYPE
-T, –print-type : print file system type

df usage Examples with options :

1. If you want to display all the file system, use -a option.

   df -a
   

   Output :

   /dev/sda10      78873504 67528540   7315320  91% /home
   /dev/sda1         507904    30908    476996   7% /boot/efi
   tmpfs             804624       12    804612   1% /run/user/121
   tmpfs             804624       64    804560   1% /run/user/1000
   gvfsd-fuse             0        0         0    - /run/user/1000/gvfs
   

   The above is not complete output, but you can see that the information shown is extended to info provided by df command.

2. Use -h option to display size in power of 1024

   df -h /home/mandeep
   

   Output :

   Filesystem      Size  Used Avail Use% Mounted on
   /dev/sda10       76G   65G  7.0G  91% /home
   

3. Use -H option to display sizes in power of 1000

   df -H /home/mandeep
   

   Output :

   Filesystem      Size  Used Avail Use% Mounted on
   /dev/sda10       81G   70G  7.5G  91% /home
   

   You can observe the size section of two command with -h and -H option for difference.

4. To get complete grand total, use –total option

   df --total
   

   Output :

   Filesystem     1K-blocks     Used Available Use% Mounted on
   udev             3996816        0   3996816   0% /dev
   tmpfs             804624    10072    794552   2% /run
   /dev/sda9       68117056 18036336  46597536  28% /
   tmpfs            4023116    50140   3972976   2% /dev/shm
   tmpfs               5120        4      5116   1% /run/lock
   tmpfs            4023116        0   4023116   0% /sys/fs/cgroup
   /dev/loop0         88832    88832         0 100% /snap/simplescreenrecorder/1
   /dev/loop2         85888    85888         0 100% /snap/core/3748
   /dev/loop3         85888    85888         0 100% /snap/core/3604
   /dev/loop1         83328    83328         0 100% /snap/core/3887
   /dev/sda10      78873504 67529320   7314540  91% /home
   /dev/sda1         507904    30908    476996   7% /boot/efi
   tmpfs             804624       12    804612   1% /run/user/121
   tmpfs             804624       64    804560   1% /run/user/1000
   total          162304440 86000792  68790820  56% -
   

   Observe the last row of above table output, it specifies grand total.

5. Use -T option to display file type
   For example:

   df -T /home/mandeep
   

   Output :

   Filesystem     Type 1K-blocks     Used Available Use% Mounted on
   /dev/sda10     ext4  78873504 67528128   7315732  91% /home
   

   You can see the file type for /home/mandeep is ext4.

6. And for more help, you can use –help option.

   df --help
   

– Mandeep Singh

References :
1) df wiki
2) Linux man page for df

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