Linux Permissions

Syntax

General: _rwxrwxrwx 1 owner group

_ | rwx | rwx | rwx = Special | Owner | Group | All Users

Shorthand

• 4 | r = Read
• 2 | w = Write
• 1 | x = Execute

Detailed

• 0 = ---
• 1 = --x
• 2 = -w-
• 3 = -wx
• 4 = r-
• 5 = r-x
• 6 = rw-
• 7 = rwx

Commands

chgrp = Change group

Example: sudo chgrp -R <group> <folder>

chown = Change ownership

Example: sudo chown -R <user>:<group> <file/folder>

chmod = Change permissions

Example: sudo chmod -R 774 <file/folder>

Make new files inherit the group: sudo chmod g+s <folder>

Example

Create a shared directory for a group.1. Create a shared directory for users to access: /share

1. Assign users to a common group (staff): sudo usermod -a -G staff <user>
2. Verify user groups: groups <user>
3. Create shared directory and assign permissions:

sudo mkdir /share && \
sudo chgrp -R staff /share && \ # assign group
sudo chmod -R g+w /share && \ # permissions
sudo chmod -R +s /share # inherit permissions for newly created files/folders