Feb 232015
 

Today let’s talk about df, the command line utility providing information on disk space used and remaining on your file systems.

Unsurprisingly, df stands for disk free.

Besides listing how much disk space is used and how much is free, df also displays how the file systems are mounted on your Linux desktop or server.

With df, you get disk use information on your local system as well as external drives attached to it.

The basic syntax of df is:

df [OPTION]… [FILE]..

One caveat I must add here is that df will not provide you with the size of directories or files. The command for that is du and we’ll cover that in a separate article.

Here are a bunch of df commands that you can grasp in less than 10 minutes.

Should you not provide any file name while running df, the space available on all mounted file systems will be displayed.

1. Basic df Command

When you run the df command without any options, the output provides disk utilization in 1K blocks.

larry@tammypc ~ $ df
Filesystem      1K-blocks      Used  Available Use% Mounted on
/dev/sda1      1918766120 157599888 1663675496   9% /
none                    4         0          4   0% /sys/fs/cgroup
udev              1925276         4    1925272   1% /dev
tmpfs              388172      1392     386780   1% /run
none                 5120         0       5120   0% /run/lock
none              1940848       788    1940060   1% /run/shm
none               102400        20     102380   1% /run/user
/dev/sdb1       244137920 205701856   38436064  93% /media/larry/HITACHI

In the above example, sda1 is the local drive and sdb1 is an external drive.

Apart from physical hard drives, df will list mounted file systems such as udev for /dev and tmpfs filesystem for /run and its subdirectories. Those with a grounding in Linux will quickly recognize that these file systems run in memory and are part of Linux.

2. Include All File Systems

The df -a command will include all file systems including those that have a size of 0 blocks, which are omitted by default (such file systems are usually special-purpose pseudo-file systems like automounter entries).

$ df -a
Filesystem      1K-blocks      Used  Available Use% Mounted on
/dev/sda1      1918766120 157529716 1663745668   9% /
proc                    0         0          0    - /proc
sysfs                   0         0          0    - /sys
none                    4         0          4   0% /sys/fs/cgroup
none                    0         0          0    - /sys/fs/fuse/connections
none                    0         0          0    - /sys/kernel/debug
none                    0         0          0    - /sys/kernel/security
udev              1925276         4    1925272   1% /dev
devpts                  0         0          0    - /dev/pts
tmpfs              388172      1408     386764   1% /run
none                 5120         0       5120   0% /run/lock
none              1940848       736    1940112   1% /run/shm
none               102400        16     102384   1% /run/user
none                    0         0          0    - /sys/fs/pstore
binfmt_misc             0         0          0    - /proc/sys/fs/binfmt_misc
systemd                 0         0          0    - /sys/fs/cgroup/systemd
gvfsd-fuse              0         0          0    - /run/user/1000/gvfs

3. Display for Specific File System

We can narrow down space used for a file system with the below command.

$ df /dev/sda1
Filesystem      1K-blocks      Used  Available Use% Mounted on
/dev/sda1      1918766120 157541184 1663734200   9%  /

4. Display in Human Readable Format

By default, df displays information in kilobytes.

Now in a world of gigabytes and terabytes hardly anybody uses kilobytes these days. So the df folks came up with the -h option.

Of all the df options, the most useful one is df -h because this gives the output in human readable format.

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1       1.8T  151G  1.6T   9% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
udev            1.9G  4.0K  1.9G   1% /dev
tmpfs           380M  1.4M  378M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            1.9G  736K  1.9G   1% /run/shm
none            100M   16K  100M   1% /run/user

I wouldn’t be surprised if df –h is the most used among the various df options.

5. Ignore Virtual File Systems

More often than not, we don’t need space use pertaining to virtual file systems.

What we are interested is are the partitions on the hard drives.

Here’s an example of how we can remove information pertaining to virtual file systems that exist only in memory:

df -h |grep ^/
/dev/sda1       1.8T  151G  1.6T   9% /
/dev/sdb1       233G  216G   18G  93% /media/larry/HITACHI

6. Display inode Usage

The below command will display inode information instead of blocks in the second column.

df -i
Filesystem        Inodes  IUsed     IFree IUse% Mounted on
/dev/sda1      121847808 261110 121586698    1% /
none              485212      2    485210    1% /sys/fs/cgroup
udev              481319    549    480770    1% /dev
tmpfs             485212    579    484633    1% /run
none              485212      1    485211    1% /run/lock
none              485212      5    485207    1% /run/shm
none              485212     22    485190    1% /run/user

7. Display Grand Total

df --total
Filesystem      1K-blocks      Used  Available Use% Mounted on
/dev/sda1      1918766120 157532132 1663743252   9% /
none                    4         0          4   0% /sys/fs/cgroup
udev              1925276         4    1925272   1% /dev
tmpfs              388172      1404     386768   1% /run
none                 5120         0       5120   0% /run/lock
none              1940848       984    1939864   1% /run/shm
none               102400        20     102380   1% /run/user
total          1923127940 157534544 1668102660   9% -

You can get a more user-friendly output by running the following command:

$ df --total -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1       1.8T  151G  1.6T   9% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
udev            1.9G  4.0K  1.9G   1% /dev
tmpfs           380M  1.4M  378M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            1.9G  984K  1.9G   1% /run/shm
none            100M   20K  100M   1% /run/user
total           1.8T  151G  1.6T   9% -

8. Display File System Types

The difference between the plain df command and df -T is that the df -T will display the type of file system too in the output. You may find this useful in certain situations.

See example below:

$df -T
Filesystem     Type      1K-blocks      Used  Available Use% Mounted on
/dev/sda1      ext4     1918766120 157526952 1663748432   9% /
none           tmpfs             4         0          4   0% /sys/fs/cgroup
udev           devtmpfs    1925276         4    1925272   1% /dev
tmpfs          tmpfs        388172      1404     386768   1% /run
none           tmpfs          5120         0       5120   0% /run/lock
none           tmpfs       1940848      1172    1939676   1% /run/shm
none           tmpfs        102400        16     102384   1% /run/user

9. Display Disk Usage of a Specific Mount Point

df /
Filesystem      1K-blocks      Used  Available Use% Mounted on
/dev/sda1      1918766120 157600360 1663675024   9% /

10. List Information for /home File System

Should you wish to see information only of the /home file system in human readable format run the below command:

$ df -hT /home
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/sda1      ext4  1.8T  151G  1.6T   9% /

11. Include Certain File System Types

The df command lets you display file systems that belong only to a certain type.

In the following example, I have specified ext4 to be included:

$ df -t ext4
Filesystem      1K-blocks      Used  Available Use% Mounted on
/dev/sda1      1918766120 157529968 1663745416   9% /

12. Exclude Certain File System Types

You can also use df with the -x option to remove certain file systems.

In the following example, I wanted the tmpfs virtual file system to be excluded in the output.

df -x tmpfs
Filesystem      1K-blocks      Used  Available Use% Mounted on
/dev/sda1      1918766120 157530172 1663745212   9% /
udev              1925276         4    1925272   1% /dev

13. Stuck with df, Seek Help

With Linux commands, even the best of us can occasionally be stumped.

Should you encounter an issue with df, run the following command for help:

$ df --help
Usage: df [OPTION]... [FILE]...
Show information about the file system on which each FILE resides,
or all file systems by default.

Mandatory arguments to long options are mandatory for short options too.
  -a, --all             include dummy file systems
  -B, --block-size=SIZE  scale sizes by SIZE before printing them.  E.g.,
                           '-BM' prints sizes in units of 1,048,576 bytes.
                           See SIZE format below.
      --total           produce a grand total
  -h, --human-readable  print sizes in human readable format (e.g., 1K 234M 2G)
  -H, --si              likewise, but use powers of 1000 not 1024
  -i, --inodes          list inode information instead of block usage
  -k                    like --block-size=1K
  -l, --local           limit listing to local file systems
      --no-sync         do not invoke sync before getting usage info (default)
      --output[=FIELD_LIST]  use the output format defined by FIELD_LIST,
                               or print all fields if FIELD_LIST is omitted.
  -P, --portability     use the POSIX output format
      --sync            invoke sync before getting usage info
  -t, --type=TYPE       limit listing to file systems of type TYPE
  -T, --print-type      print file system type
  -x, --exclude-type=TYPE   limit listing to file systems not of type TYPE
  -v                    (ignored)
      --help     display this help and exit
      --version  output version information and exit

Getting the hang of df is no sweat.

Fortunately, df is not like fail2ban or iptables, which are more complex command line tools.

Go ahead, take df for a spin on your terminal now.

 Posted by at 5:56 pm

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