du is an abbreviation for (Disk Usage), this command calculates & returns the size of entire directory tree as well as of individual files. df is an abbreviation for (Disk Free), it's job is to calculate and return the amount of free space of a disk/partition.
These two commands report space usage & free space by filesystem block and not the actual size of the file, but the actual space that it uses on the disk.
The du & df commands are generally used by system administrators to monitor & alert storage's volumes to prevent program crashes due to disk space issues.
All following examples are based on this directory:
Now, we'll see the most basic usage of du, we'll use the -a option to report usage on a per-file basis, instead of just displaying the total size of a directory.
The size is displayed in bytes, but we might want to display the sizes in human readable format.
There are 2 more important options, s (summarize or suppress) & c options. See the examples below.
The s only shows the total size, and the c option show the total in the end.
We might at times want to exclude some files, or some types of files from the calculation.
The most common use of df is to display summary of all partitions in the system.
You may also also use df checking free space on individual partitions, either by specifying the device or the directory.
At times it might happen that df & du might report data that is not matching, this usually occurs due to open file descriptors, you can check these using the lsof command.
These two commands report space usage & free space by filesystem block and not the actual size of the file, but the actual space that it uses on the disk.
The du & df commands are generally used by system administrators to monitor & alert storage's volumes to prevent program crashes due to disk space issues.
Disk Usage
All following examples are based on this directory:
Code: bash
[pradeep@castellano]$ ls -l
total 56
-rw-r--r-- 1 pradeep pg1555168 3355 2011-07-22 05:19 1311337262_info.png
-rwxr-xr-x 1 pradeep pg1555168 1227 2011-07-30 01:54 android.pl
-rw-rw-r-- 1 pradeep pg1555168 5076 2011-07-22 07:00 android_apps.html
-rw-r--r-- 1 pradeep pg1555168 3430 2011-07-29 06:34 apps.dat
drwxrwxr-x 2 pradeep pg1555168 4096 2012-07-09 04:58 images
-rw-r--r-- 1 pradeep pg1555168 4599 2011-07-22 04:54 info_icon.png
-rw-r--r-- 1 pradeep pg1555168 3374 2011-07-29 05:14 jquery.lightbox_me.js
-rw-rw-r-- 1 pradeep pg1555168 101 2009-06-25 02:03 llsh.gif
-rw-r--r-- 1 pradeep pg1555168 1742 2011-07-30 01:57 main.tpl.html
-rwxrwxr-x 1 pradeep pg1555168 3741 2012-04-30 03:31 ssearch.pl
-rw-rw-r-- 1 pradeep pg1555168 1830 2011-07-29 07:03 style.css
-rw-rw-r-- 1 pradeep pg1555168 117 2009-06-25 02:03 teaser.gif
Now, we'll see the most basic usage of du, we'll use the -a option to report usage on a per-file basis, instead of just displaying the total size of a directory.
Code: bash
[pradeep@castellano]$ du
16 ./images
76 .
[pradeep@castellano]$ du -a
4 ./1311337262_info.png
4 ./android.pl
8 ./android_apps.html
4 ./ssearch.pl
4 ./teaser.gif
4 ./main.tpl.html
4 ./style.css
4 ./llsh.gif
8 ./info_icon.png
4 ./.htaccess
4 ./apps.dat
4 ./images/1311337262_info.png
4 ./images/teaser.gif
4 ./images/llsh.gif
16 ./images
4 ./jquery.lightbox_me.js
76 .
The size is displayed in bytes, but we might want to display the sizes in human readable format.
Code: bash
[pradeep@castellano]$ du -ah
4.0K ./1311337262_info.png
4.0K ./android.pl
8.0K ./android_apps.html
4.0K ./ssearch.pl
4.0K ./teaser.gif
4.0K ./main.tpl.html
4.0K ./style.css
4.0K ./llsh.gif
8.0K ./info_icon.png
4.0K ./.htaccess
4.0K ./apps.dat
4.0K ./images/1311337262_info.png
4.0K ./images/teaser.gif
4.0K ./images/llsh.gif
16K ./images
4.0K ./jquery.lightbox_me.js
76K .
There are 2 more important options, s (summarize or suppress) & c options. See the examples below.
Code: bash
[pradeep@castellano]$ du -hs
76K .
[pradeep@castellano]$ du -ahc *.png
4.0K 1311337262_info.png
8.0K info_icon.png
12K total
The s only shows the total size, and the c option show the total in the end.
We might at times want to exclude some files, or some types of files from the calculation.
Code: bash
[pradeep@castellano]$ du -ahc --exclude='*.png'
4.0K ./android.pl
8.0K ./android_apps.html
4.0K ./ssearch.pl
4.0K ./teaser.gif
4.0K ./main.tpl.html
4.0K ./style.css
4.0K ./llsh.gif
4.0K ./.htaccess
4.0K ./apps.dat
4.0K ./images/teaser.gif
4.0K ./images/llsh.gif
12K ./images
4.0K ./jquery.lightbox_me.js
60K .
60K total
Disk Free
The most common use of df is to display summary of all partitions in the system.
Code: bash
[pradeep@castellano]$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 60G 43G 14G 76% /
tmpfs 7.9G 0 7.9G 0% /lib/init/rw
tmpfs 7.9G 5.6M 7.9G 1% /dev/shm
/dev/sda2 3.8G 168M 3.6G 5% /tmp
/dev/sda6 92M 5.7M 81M 7% /var/spool/cron/crontabs
/dev/sdb1 3.6T 3.5T 92G 98% /home
You may also also use df checking free space on individual partitions, either by specifying the device or the directory.
Code: bash
[pradeep@castellano]$ df /
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 62009668 44463052 14396676 76% /
[pradeep@castellano]$ df /tmp/
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda2 3937252 171544 3765708 5% /tmp
[pradeep@castellano]$ df /dev/sdb1
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sdb1 3758537404 3664210776 94326628 98% /home
Caveats
At times it might happen that df & du might report data that is not matching, this usually occurs due to open file descriptors, you can check these using the lsof command.
