Octal Numbers in Linux Filesystem Permissions

• octal numbers - 0-7

• adding up 4, 2 or 1 (always a unique combination)

• set user ID (setuid) - 4
• set group ID (setgid) - 2
• sticky - 1
• owner user read - 4
• owner user write - 2
• owner user execute - 1
• users in group read - 4
• users in group write - 2
• users in group execute - 1
• other users read - 4
• other users write - 2
• other users execute - 1