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.
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.
