Linux Permission Manipulation

Need a quick reference guide to linux commands for manipulating file and directory permissions?

Common Commands

To find the owner(s) of a directory:

ls -l | awk '{print $3, $4 }' | sort | uniq

To change the permissions:

chmod 600 filename

To change permissions by user type (use ‘+’ or ‘-’):

chmod a+w filename

To change ownership (only from superuser):

chown user_to_assign filename

To change group assignment:

chgrp groupname filename

Common settings

Permission definitions:

Files:  r- read                              w- write           x- execute
Dir:    r- directory can be listed if x      w- writable if x   x- directory can be entered


600 (rw-------): only owner can read/write
644 (rw-r--r--): owner- can read/write; others- read only
666 (rw-rw-rw-): all users can read/write
700 (rxw------): owner- can read/write/execute; no one else can do anything with it
755 (rwxr-xr-x): owner- can read/write/execute; everyone else- read/execute
777 (rwxrwxrwx): all users have all permissions

(Note: Numbers starting with ‘7’ enable execution and are used for program files.)


u =>    you
g =>    group
o =>    others
a =>    all (all of the above- ugo)
su =>   superuser (switches to root user)
sudo => superuser (runs single command with root privileges)