General Information

About this page/how-to/script.

Permissions tools

• chmod ⇒ Change permissions for user, group, other, or all
• chown ⇒ Change user/group ownership

Chmod Modes

• symbolic ⇒ represent permissions via u,g,o,a
• octal ⇒ represent permissions with numbers

Change file1 ownership to rjones and group to student

chown rjones:student file1

• You can leave off either the username or group name if only changing one of them, but the colon (:) must remain if only changing the group owner.

ls -l
-rw-r--r--. 2 root root          0 Jun 20 15:11 file1
-rw-r--r--. 2 root root          0 Jun 20 15:11 file2
drwxr-xr-x. 3 root root         17 Jun 20 14:50 newdir

• First column ⇒ - (file), d (directory, l (symlink)
• Columns 2-4 ⇒ User owner permissions (rwx)
• Columns 5-7 ⇒ Group permissions (rwx)
• Columns 8-10 ⇒ Other permissions (rwx)

• u ⇒ user owner
• g ⇒ group
• o ⇒ other users
• a ⇒ all users

Add write permissions to a file for the group

chmod g+w file1

Take away read permissions for others, for all of dir1 directory and its contents

chmod -R o-r dir1

• -R ⇒ recursively

Add execute permissions to directories only in a tree

chmod -R ug+X dir1

• For user owner and group ⇒ Adds execute to dir1 and all sub directories, not files.

• 4 ⇒ read
• 2 ⇒ write
• 1 ⇒ execute
• Add together to get permissions

Set file1 permissions using octal notation

chmod 740 file1

• user owner ⇒ read(4),write(2),execute(1) permissions (4+2+1=7)
• group ⇒ read(4) permissions
• others ⇒ no(0) permissions