There might come a situation while using Linux when you want to know the amount of space consumed by a particular file system on your LINUX system or how much space is available on a particular file system. LINUX being command friendly provides a command line utility for this i.e df command that displays the amount of disk space available on the file system containing each file name argument.
- If no file name is passed as an argument with df command then it shows the space available on all currently mounted file systems
- . This is something you might wanna know cause df command is not able to show the space available on unmounted file systems and the reason for this is that for doing this on some systems requires very deep knowledge of file system structures.
- By default, df shows the disk space in 1 K blocks.
- df displays the values in the units of first available SIZE from –block-size (which is an option) and from the DF_BLOCK_SIZE, BLOCKSIZE AND BLOCK_SIZE environment variables.
- By default, units are set to 1024 bytes or 512 bytes(if POSIXLY_CORRECT is set) . Here, SIZE is an integer and optional unit and units are K, M, G, T, P, E, Z, Y (as K in kilo) .
df Syntax :
df [OPTION]...[FILE]... OPTION : to the options compatible with df command FILE : specific filename in case you want to know the disk space usage of a particular file system only.
Using df command
Suppose you have a file named kt.txt and you want to know the used disk space on the file system that contains this file then you can use df in this case as:
// using df for a specific file // $df kt.txt Filesystem 1K-blocks Used Available Use% Mounted on /dev/the2 1957124 1512 1955612 1% /snap/core /* the df only showed the disk usage details of the file system that contains file kt.txt */
Now, what if you don’t give any filename t df, in that case df displays the disk usage information for all mounted file systems as shown below:
//using df without any filename // $df Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 18761008 15246876 2554440 86% / none 4 0 4 0% /sys/fs/cgroup udev 493812 4 493808 1% /dev tmpfs 100672 1364 99308 2% /run none 5120 0 5120 0% /run/lock none 503352 1764 501588 1% /run/shm none 102400 20 102380 1% /run/user /dev/the2 1957124 1512 1955612 1% /snap/core /* in this case df displayed the disk usage details of all mounted file systems */
Options for df command
- -a,- -all : It includes all the dummy files also in the output which are actually having zero block sizes.
- -B,- -block-size=S : This is the option we were talking in the above para which is used to scale sizes by SIZE like -BM prints sizes in units of 1,048,576 bytes.
- – -total : It is used to display the grand total for size.
- -h,- -human-readable : It print sizes in human readable format.
- -H,- -si : This option is same as -h but it use powers of 1000 instead of 1024.
- -i,- -inodes : This option is used when you want to display the inode information instead of block usage.
- -k : Its use is like –block-size-1k.
- -l,- -local : This will display the disk usage of only local file systems.
- -P,- -portability : It uses the POSIX output format.
- -t,- -type=TYPE : It will only show the output of file systems having type TYPE.
- -T,- -print-type : This option is used to print file system type shown in the output.
- -x,- -exclude-type=TYPE : It will exclude all the file systems having type TYPE from the output.
- -v : Ignored, included for compatibility reasons.
- – -no-sync : This is the default setting i.e not to invoke sync before getting usage info.
- – -sync : It invokes a sync before getting usage info.
- – -help : It displays a help message and exit.
- – -version : It displays version information and exit.
Examples of using df with options
1. Using -a : If there is a need to display all file systems along with those which has zero block sizes then use -a option with df.
//using df with -a// $df -a Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 18761008 15246876 2554440 86% / none 4 0 4 0% /sys/fs/cgroup udev 493812 4 493808 1% /dev tmpfs 100672 1364 99308 2% /run none 5120 0 5120 0% /run/lock none 503352 1764 501588 1% /run/shm none 102400 20 102380 1% /run/user /dev/sda3 174766076 164417964 10348112 95% /host systemd 0 0 0 - /sys/fs/cgroup /* in this case systemd file system having zero block size is also displayed */
2. Using -h : This is used to make df command display the output in human-readable format.
//using -h with df// $df -h kt.txt Filesystem 1K-blocks Used Available Use% Mounted on /dev/the2 1.9G 1.5M 1.9G 1% /snap/core /*this output is easily understandable by the user and all cause of -h option */
In the above, G and M represents Gigabytes and Megabytes respectively. You can use -h with df only to produce the output in readable format for all the mounted file systems rather than just of the file system containing kt.txt file.
3. Using -k : This displays the file system information and usage in 1 K blocks.
//using -k with df// $df -k kt.txt Filesystem 1K-blocks Used Available Use% Mounted on /dev/the2 1957124 1512 1955612 1% /snap/core /* no change cause the output was initially shown in the usage of 1K bytes only */
4. Using – -total : This option is used to produce total for a size, used and available columns in the output.
//using --total with df// $df --total Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 18761008 15246876 2554440 86% / none 4 0 4 0% /sys/fs/cgroup udev 493812 4 493808 1% /dev tmpfs 100672 1364 99308 2% /run none 5120 0 5120 0% /run/lock none 503352 1764 501588 1% /run/shm none 102400 20 102380 1% /run/user /dev/the2 1957124 1512 1955612 1% /snap/core total 21923492 15251540 5712260 92% - /* the total row is added in the output */
5. Using -T : With the help of this option, you will be able to see the corresponding type of the file system as shown.
/using -T with df// $df -T kt.txt Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/the2 squashfs 1957124 1512 1955612 1% /snap/core /* you can use -T with df only to display type of all the mounted file systems */
6. Using -t : This is used when you wish the disk usage information of the file systems having a particular type only.
//using -t with df// $df -t squashfs Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 18761008 15246876 2554440 86% / /dev/the2 1957124 1512 1955612 1% /snap/core /*so the df displayed only the info of the file systems having type squashfs */
7. Using -x : Now, you can also tell df to display the disk usage info of all the file systems except those having a particular type with the help of -x option.
//using -x with df// $df -x squashfs Filesystem 1K-blocks Used Available Use% Mounted on none 4 0 4 0% /sys/fs/cgroup udev 493812 4 493808 1% /dev tmpfs 100672 1364 99308 2% /run none 5120 0 5120 0% /run/lock none 503352 1764 501588 1% /run/shm none 102400 20 102380 1% /run/user /* in this case info of /dev/the2 and /dev/loop0 file systems aren't displayed cause they are of type squashfs */
8. Using -i : This option is used to display inode information in the output.
//using -i with df// $df -i kt.txt Filesystem Inodes IUsed IFree Iuse% Mounted on /dev/the2 489281 48 489233 1% /snap/core /*showing inode info of file system having file kt.txt */
When -i option is used then the second, third, and fourth columns displays inode-related figures instead of disk related.
9. Using – -sync : By default, the df command produces output with – -no-sync option which will not perform the sync system call prior to reporting usage information. Now we can use – -sync option which will force a sync resulting in the output being fully up to date.
//using --sync option// $df --sync Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 18761008 15246876 2554440 86% / none 4 0 4 0% /sys/fs/cgroup udev 493812 4 493808 1% /dev tmpfs 100672 1364 99308 2% /run none 5120 0 5120 0% /run/lock none 503352 1764 501588 1% /run/shm none 102400 20 102380 1% /run/user /dev/the2 1957124 1512 1955612 1% /snap/core /* in this case no change in the output is observed cause it is possible that there is no update info present to be reflected */
10. Using -l : When we run df command then by default it shows any externally mounted file systems which include those from external NFS or Samba servers. We can hide the info of these external file systems from output with -l option syntax of which is shown below.
$df -l
So, this is all about df command.