Chmod Calculator
Calculate Linux chmod permissions visually. Convert between rwx and octal formats with our free chmod calculator.
Advertisement
Advertisement
Linux File Permissions
Linux file permissions control who can read, write, or execute files. Every file and directory has three permission sets: owner (user), group, and others — each with three bits for read (r), write (w), and execute (x).
Permission Bits
- r (read) = 4 — view file contents or list directory
- w (write) = 2 — modify file contents or create/delete in directory
- x (execute) = 1 — run file as program or enter directory
- Sum the values: rwx = 4+2+1 = 7, r-x = 4+0+1 = 5
Common Permission Codes
755(rwxr-xr-x) — web files and scripts: owner full, others read+execute644(rw-r--r--) — static files: owner read+write, others read only600(rw-------) — private files: owner only (SSH keys)777(rwxrwxrwx) — everyone full access (avoid in production)
What does chmod 755 mean?
chmod 755 sets: owner = rwx (7), group = r-x (5), others = r-x (5). The owner can read, write, and execute; everyone else can read and execute but not write. This is the standard permission for web server scripts and executable files.
What are special permission bits (setuid, setgid, sticky)?
A 4th octal digit controls special bits: setuid (4) runs the file as the owner's user, setgid (2) runs it as the group, and sticky bit (1) prevents deletion by non-owners (used on /tmp). Example: chmod 4755 sets setuid + normal 755.
How do I apply permissions recursively?
Use chmod -R 755 /path/to/dir to apply permissions recursively to all files and subdirectories. Be careful — applying 755 recursively to a directory with files may give execute permission to files that don't need it; use find to apply different permissions to files vs directories.