Linux Permissions Calculator

Interactive Permission Grid

Read (r/4)

Write (w/2)

Execute (x/1)

Owner

Group

Others

Permission Display

Octal Notation

644

Symbolic Notation

rw-r--r--

Full ls -l Style

-rw-r--r--

Owner rw-

6/7

Group r--

4/7

Others r--

4/7

Reverse Calculator

Enter Octal (e.g., 755)

Symbolic Breakdown

Enter octal above

Explanation

Enter a 3-digit octal number to see the symbolic breakdown.

chmod Command Generator

Filename (optional)

Numeric Format

chmod 644 filename

Symbolic Format

chmod u=rw,g=r,o=r filename

Common Permission Presets

Special Permissions

Special permissions are added as a fourth digit before the standard permission octal. They provide advanced functionality for executable files and directories.

SUID (Set User ID)

4000

When set on an executable file, the file runs with the permissions of the file owner rather than the user executing it. Commonly used for programs like passwd that need elevated privileges. Displayed as s in owner execute position (e.g., rwsr-xr-x).

Enable SUID

SGID (Set Group ID)

2000

On executables: runs with the group permissions of the file's group. On directories: files created inherit the directory's group rather than the creator's primary group. Displayed as s in group execute position (e.g., rwxr-sr-x).

Enable SGID

Sticky Bit

1000

When set on a directory, only the file owner, directory owner, or root can delete or rename files within that directory. Commonly used on /tmp to prevent users from deleting others' files. Displayed as t in others execute position (e.g., rwxr-xr-t).

Enable Sticky Bit

Combined Special Permission Value

Combined with Standard Permissions

Full 4-Digit Octal (Special + Standard)

0644

chmod Command with Special Permissions

chmod 0644 filename

Security Warning

Special permissions, particularly SUID and SGID on executables, can create security vulnerabilities if misused. Only set these on trusted executables from reliable sources. A compromised SUID binary can lead to privilege escalation attacks.