Here are some notes on the various ways to check disk space usage on linux:

Disk usage of all (non-hidden) files and folders

Using the du command (disk use) with the -s (summarize) and -h (human-readable) options.

du -sh *

Prints a list of all files and folders in the current directory. Folder/directory sizes given includes all the subdirectories and any files they contain.

BONUS: You can add the -c option to get the total size of all the files that this command lists. (I.e. du -sch *)

Total disk usage including hidden files

This is useful, particularly if you are trying to get comparable outputs from the quota command (see below). Hidden files are not included by default, so we have to use wildcard matching like so:

du -sch .[!.]* *

The first . matches files beginning with a dot, but we want to exclude .., since this would match the directory above (as in when you do cd .. etc.) and we don’t want to include that. To exclude that pattern we add [!.], in other words, match a single dot but not two in a row. The final asterisk is to match all the non-hidden files as before.

Another way to do this is to specify the -ahd1 set of options:

du -ahd1

However, this also includes the file ., which refers to the current directory. If you add the -c option to this

Sorted disk usage

The easiest way to do this is to just pipe the results into the sort command. To sort them numerically, we can just add the -n flag to sort.

du -sch * | sort -n

This will sort them numerically in ascending order. Have a look at the sort manual pages for more sorting opttions.

Disk usage by file system

df is a slightly different unix command which lists disk free space by file system. Typing it with no options will give a list of all mounted file systems, their total size available, how much space has been used, and their linux mount points. The -h option gives a more human-readable form.

df -h

Disk quota information

On systems where you have an allocated disk quota, the quota utility tells you how much of your quota has been used and how much you have available. The -s option gives a nice summary of disk quota:

quota -s

Outputs:

Disk quotas for user bob (uid 123456): 
     Filesystem   space   quota   limit   grace   files   quota   limit   grace
mydomain:/disk/someserver/u1234//dvalters
                  2000M  15000M  15000M           12000       0       0

The space output is sometimes replaced with blocks, which is a slightly less helpful measure. On POSIX systems, 1 block is befined as 512 bytes. space (or blocks tells you how much you have used, quota is your total quota allowance. If you are over the quota, an asterisk appears next to the number for space/blocks.

Other utilities

I have only covered the most common GNU/Linux utilities for monitoring/measuring disk usage. There are othe utilities available that have nicer outputs by default, such as: ncdu, freespace etc.