Chmod & Chown Permission Calculator
Calculate octal numbers, symbolic strings, and binary bits for Linux file permissions. Generate accurate chmod and chown terminal commands instantly.
755
-rwxr-xr-x
Regular file
111 101 101
Owner • Group • Others
Permissions Matrix
Linux Command Generator
Mastering Linux Permissions & Octal Notation
1. The 4-2-1 Octal Math
Each digit in an octal permission mode represents the sum of three distinct permission bits: Read (4), Write (2), and Execute (1). For example, 7 = 4+2+1 (rwx), and 5 = 4+1 (r-x).
2. User, Group & Others Triad
A standard 3-digit octal number assigns permissions to three discrete scopes: the file owner (User), members of the file's assigned (Group), and everyone else on the system (Others).
3. Special Bits (SUID, SGID, Sticky)
Prefixed as a fourth octal digit: SUID (4) executes with the file owner's credentials; SGID (2) inherits group ownership; and the Sticky Bit (1) prevents non-owners from deleting files in shared directories like /tmp.
Standard Linux Permissions Reference
| Octal | Symbolic | Standard Purpose | Security Note |
|---|---|---|---|
| 644 | -rw-r--r-- | Static web assets, CSS, images, docs | Safe: Owner can edit, others read-only |
| 755 | -rwxr-xr-x | Bash scripts, binaries, public folders | Standard for executables & directories |
| 600 | -rw------- | SSH private keys (~/.ssh/id_rsa), SSL certs | Restricted: Only owner can view or edit |
| 777 | -rwxrwxrwx | World-writable everything (Anti-pattern) | Dangerous: Any system user can overwrite or inject code |