CHOWN and CHMOD Examples

Change the owner of a file

# ls -lart tmpfile [ls is used to diplay the file/directory properties]
-rw-r--r-- 1 himanshu family 0 2012-05-22 20:03 tmpfile
# chown root tmpfile
# ls -l tmpfile
-rw-r--r-- 1 root family 0 2012-05-22 20:03 tmpfile

Change the group of a file

Through the chown command, the group (that a file belongs to) can also be changed.
# ls -l tmpfile
-rw-r--r-- 1 himanshu family 0 2012-05-22 20:03 tmpfile
# chown :friends tmpfile
# ls -l tmpfile
-rw-r--r-- 1 himanshu friends 0 2012-05-22 20:03 tmpfile

Change both owner and the group

# ls -l tmpfile
-rw-r--r-- 1 root family 0 2012-05-22 20:03 tmpfile
# chown himanshu:friends tmpfile
# ls -l tmpfile
-rw-r--r-- 1 himanshu friends 0 2012-05-22 20:03 tmpfile

Change owner only if a file is owned by a particular user

Using chown “–from” flag, you can change the owner of a file, only if that file is already owned by a particular owner.

# ls -l tmpfile
-rw-r--r-- 1 root friends 0 2012-05-22 20:03 tmpfile
# chown --from=guest himanshu tmpfile
# ls -l tmpfile
-rw-r--r-- 1 root friends 0 2012-05-22 20:03 tmpfile
# chown --from=root himanshu tmpfile
# ls -l tmpfile
-rw-r--r-- 1 himanshu friends 0 2012-05-22 20:03 tmpfile

◾In the example above, we verified that the original owner/group of the file ‘tmpfile’ was root/friends. ◾Next we used the ‘–from’ flag to change the owner to ‘himanshu’ but only if the existing owner is ‘guest’. ◾Now, as the existing owner was not ‘guest’. So, the command failed to change the owner of the file. ◾Next we tried to change the owner if the existing owner is ‘root’ (which was true) and this time command was successful and the owner was changed to ‘himanshu’.