When you're trying to clean up your filesystems and reclaim some space, one of the first things you'll want to do is to confirm the largest directories and individual files you have. This can be easily done using two Unix commands: find command and du command.
Find files larger than a certain size
It's very simply to find files which are larger than a specified size. The find command accepts a size parameter, and you can specify the limits for file sizes in your command line.
This example finds all the files under /etc directory which are larger than 100k:
root@ubuntu# find /etc -size +100k /etc/ssh/moduli /etc/ssl/certs/ca-certificates.cr /etc/bash_completio
If we look at their sizes, they really are above 100k:
root@ubuntu# ls -l /etc/ssh/moduli /etc/ssl/certs/ca-certificates.crt /etc/bash_completio -rw-r--r-- 1 root root 215938 Apr 10 2007 /etc/bash_completion -rw-r--r-- 1 root root 132777 Feb 19 2007 /etc/ssh/moduli -rw-r--r-- 1 root root 149568 Sep 7 2007 /etc/ssl/certs/ca-certificates.crt
Find files within specified size limits
The real beauty of using find command is that you can specify both the lower and the upper file size limit in one command line. Working off the previous example, we can limit the search to find only files with the size of 100k-150k, quite easily:
root@ubuntu# find /etc -size +100k -size -150k /etc/ssl/certs/ca-certificates.crt /etc/bash_completion
As you can see from the syntax, the size specification can contain a sign – plus or minus indicates whether you're looking for a file with the size above or under a given figure.
Show directory sizes using du
du command takes a little while to run, depending on what directory you pass it as a parameter, but then prints you a list of all the subdirectories along with their sizes. Most common usage is shown below, -s parameter makes the command report a summary of disk usage stats for only the specified directories matching the /usr/* mask (and not their subdirectories), and -k specifies that we want to see the results in kilobytes:
root@ubuntu# du -sk /usr/* 90824 /usr/bin 4 /usr/games 23644 /usr/include 404196 /usr/lib 0 /usr/lib64 116 /usr/local 22020 /usr/sbin 309516 /usr/share 301600 /usr/src
In most Linux systems, this command had been updated to support a -h parameter, which makes sizes even easier to interpret:
root@ubuntu# du -sh /usr/* 89M /usr/bin 4.0K /usr/games 24M /usr/include 395M /usr/lib 0 /usr/lib64 116K /usr/local 22M /usr/sbin 303M /usr/share 295M /usr/src
Sorting directory sizes
Now, the previous example would get a lot more useful if you sort the directories by their size. The only problem is that sort -n (numerical sorting) would sort by numbers but ignore the human-readable element (M for megabytes, K for kilobytes, G for gigabytes) thus giving you a complete mess:
root@ubuntu# du -sh /usr/* | sort -n 0 /usr/lib 644.0K /usr/games 22M /usr/sbin 24M /usr/include 89M /usr/bin 116K /usr/local 295M /usr/src 303M /usr/share 395M /usr/lib
So what do we to? Luckily for us, Linux implementation of sort supports -h option which does exactly the kind of sorting we needed:
root@ubuntu# du -sh /usr/* | sort -h 0 /usr/lib 644.0K /usr/games 116K /usr/local 22M /usr/sbin 24M /usr/include 89M /usr/bin 295M /usr/src 303M /usr/share 395M /usr/lib