CHGRP & CHOWN

Change Group Ownership with chgrp

The chgrp command is used to change the group with which a file is associated. The first thing you will need to provide this command is the group which you want to change the file or directory to. After that you can list a single file or directory to be changed or list separate entities separated by spaces. The chgrp command will not have any affect on the access granted to the group (the rw- in the middle of the three permissions sets) but will change who can use those permissions.
Using the chgrp Command on a File
# ls -l
total 12
-rw-rw-r– 1 tclark authors 2229 Jan 13 21:35 declaration.txt
-rw-rw-r– 1 tclark authors 1310 Jan 13 17:48 gettysburg.txt
-rw-rw-r– 1 tclark authors 360 Jan 13 17:48 preamble.txt
# chgrp presidents gettysburg.txt
# ls -l
total 12
-rw-rw-r– 1 tclark authors 2229 Jan 13 21:35 declaration.txt
-rw-rw-r– 1 tclark presidents 1310 Jan 13 17:48 gettysburg.txt
-rw-rw-r– 1 tclark authors 360 Jan 13 17:48 preamble.txt
The chgrp command works the same for directories as it does for files. In the following example, the group ownership of the directory called examples will be changed. Directories are identified by the letter d in the first column of the ls –l display.
Using the chgrp Command on a Directory
# ls -l
total 4
-rw-rw-r– 1 tclark tclark 0 Jan 13 21:13 example1.fil
-rw-rw-r– 1 tclark tclark 0 Jan 13 21:13 example2.xxx
drwxrwxr-x 2 tclark tclark 4096 Jan 13 21:35 examples
# chgrp authors examples
# ls -l
total 4
-rw-rw-r– 1 tclark tclark 0 Jan 13 21:13 example1.fil
-rw-rw-r– 1 tclark tclark 0 Jan 13 21:13 example2.xxx
drwxrwxr-x 2 tclark authors 4096 Jan 13 21:35 examples
You can change the group for multiple files and/or directories by using the –R(recursive) option for the chgrp command. This is one of the few commands (we’ll see two of the others shortly) which use an upper-case R for the recursive option. When applied on a directory the –R option will apply thechgrp command to the directory and all its subdirectories and files. Care should be taken when using the –R option.
Next we’ll look at changing the ownership of files.

Change User Ownership

The chown (change owner) command can be used to change ownership of a file or directory. The syntax is very similar to chgrp.
# ls -l
total 12
-rw-rw-r– 1 tclark authors 2229 Jan 13 21:35 declaration.txt
-rw-rw-r– 1 tclark authors 1310 Jan 13 17:48 gettysburg.txt
-rw-rw-r– 1 tclark authors 360 Jan 13 17:48 preamble.txt
# chown abe gettysburg.txt
# ls -l
total 12
-rw-rw-r– 1 tclark authors 2229 Jan 13 21:35 declaration.txt
-rw-rw-r– 1 abe authors 1310 Jan 13 17:48 gettysburg.txt
-rw-rw-r– 1 tclark authors 360 Jan 13 17:48 preamble.txt
Just like with chgrp we see that chown accepts the username of the user who should get ownership and the file or directory to change. Again we could list multiple files or directories here with spaces separating them.
The chown command can be used to change the group ownership instead of the user ownership of a file or directory. If you wish to use chown to change the group ownership you can list a group preceded with either a colon (:) or a period (.). Here’s an example of how to use chown to change the group ownership of a file:
# ls -l
total 12
-rw-rw-r– 1 tclark authors 2229 Jan 13 21:35 declaration.txt
-rw-rw-r– 1 abe authors 1310 Jan 13 17:48 gettysburg.txt
-rw-rw-r– 1 tclark authors 360 Jan 13 17:48 preamble.txt
# chown :presidents gettys*
# ls -l
total 12
-rw-rw-r– 1 tclark authors 2229 Jan 13 21:35 declaration.txt
-rw-rw-r– 1 abe presidents 1310 Jan 13 17:48 gettysburg.txt
-rw-rw-r– 1 tclark authors 360 Jan 13 17:48 preamble.txt
If you wish to simultaneously change both the user and group ownership of a file you can specify the user and group in the format of user:group.
In the following example the user will be changed back to tclark and the group back to authors using a single command.
Using the chown Command to Change File Ownership
# ls -l
total 12
-rw-rw-r– 1 tclark authors 2229 Jan 13 21:35 declaration.txt
-rw-rw-r– 1 abe presidents 1310 Jan 13 17:48 gettysburg.txt
-rw-rw-r– 1 tclark authors 360 Jan 13 17:48 preamble.txt
# chown tclark:authors gettys*
# ls -l
total 12
-rw-rw-r– 1 tclark authors 2229 Jan 13 21:35 declaration.txt
-rw-rw-r– 1 tclark authors 1310 Jan 13 17:48 gettysburg.txt
-rw-rw-r– 1 tclark authors 360 Jan 13 17:48 preamble.txt
Here we see the user and group has been changed with a single command. Just like with chgrp the chown command will take the –R (recursive) option and apply the chown command to a directory and its subdirectories. This should be used with care.

reference:http://www.dba-oracle.com/linux