This is a chown help file to give you a quick help on how to use the chown
command.  If you've read my chmod help file this one could be 
considered a follow up.

As before we'll work with the somefile file and somedir directory

~# ls -l 
total 456 
drwx------    7 root     root         4096 Feb 24 05:50 somedir
-rw-rw-rw-    4 root     root          323 Feb 18 09:10 somefile

As in the file chmod we are only interested in part of this output,
however since it's easier to follow in this format I'll keep it as such

Now this time all we are looking at is the two words in the middle
namely root and root.  These are the owner or user and group respectivly

The ownership and groups in combination with the permissions give
us the access permissions that is so important in a file system.

chown is a pretty simple tool with a really easy task, so there is really
only a few options and they are quite easy to explain.  chown stands for
CHange Ownership, ownership can be applied to user or groups so it can
change both.  There is also a util called chgrp which changes groups,
however since it does basicly only this and is no faster then chown
I can't see why anyone would use it myself.

To change users ownership it's chown username file or directory
chown bob somedir gives us:

drwx------    7 bob      root         4096 Feb 24 05:50 somedir

To change group ownership it's chown .group file or directory
chown users somefile gives us:

-rw-rw-rw-    4 root     users         323 Feb 18 09:10 somefile

Pretty simple huh?

Want to combine them, chown bob.users somedir produces, you guessed it

drwx------    7 bob      users        4096 Feb 24 05:50 somedir

The most common addon to this would be -R (recursive) so if you told
it you change somedir it wouid change the ownership of every file and
directory under somedir like so
chown -R bob.users somedir also produces

drwx------    7 bob      users        4096 Feb 24 05:50 somedir

But in addition a ls -l somedir we see:

total 36
-rwxr-xr-x   1 bob      users       30361 Apr  7 08:50 somefile
-rwxr-xr-x   1 bob      users         104 Mar 25 04:29 somefile2

Not a really hard tool to use is it?

As with chmod however there is also some limits.  You can't change
the user ownership of a file unless you are root and you can't change
the group to a group that you aren't a part of unless you are root.