chmod Calculator — Linux File Permissions Reference and Octal Code Builder
🔐 chmod Calculator
Build Linux file permissions visually. Click the bits or type an octal code. Includes chmod commands, special bits, and a common permissions reference.
Permission Builder
Owner (u)
Group (g)
Other (o)
📖Read (r)
✏️Write (w)
▶️Execute (x)
0
Owner
·
0
Group
·
0
Other
———-
chmod 000 file
chmod -R 000 /directory
Execute as file owner. Use on binaries (sudo, passwd).
Execute as file group. On dirs: new files inherit group.
Only owner can delete files. Used on /tmp.
Octal → Permissions
Quick Presets — click to load
Bit Values
4
r
Read
2
w
Write
1
x
Execute
4
s
Setuid
2
s
Setgid
1
t
Sticky
Symbolic Examples
chmod u+x file # Add execute for owner
chmod g-w file # Remove write from group
chmod o=r file # Set other to read-only
chmod a+x script # Add execute for all (a = ugo)
chmod u=rwx,g=rx,o= # Set explicit (= replaces)
chmod g-w file # Remove write from group
chmod o=r file # Set other to read-only
chmod a+x script # Add execute for all (a = ugo)
chmod u=rwx,g=rx,o= # Set explicit (= replaces)
Common Permissions Reference
| Octal | String | Who can do what | Typical use |
|---|---|---|---|
| 777 | rwxrwxrwx | Everyone: read, write, execute | ⚠️ Avoid in prod — world-writable |
| 755 | rwxr-xr-x | Owner: full. Group+Other: read+execute | Executables, web directories |
| 750 | rwxr-x— | Owner: full. Group: read+execute. Other: none | Private scripts shared with a group |
| 700 | rwx—— | Owner: full. Group+Other: none | Private scripts, SSH config dir |
| 664 | rw-rw-r– | Owner+Group: read+write. Other: read-only | Shared files in a group project |
| 644 | rw-r–r– | Owner: read+write. Group+Other: read-only | Web files, config files, most files |
| 640 | rw-r—– | Owner: read+write. Group: read. Other: none | Config files with secrets (DB password files) |
| 600 | rw——- | Owner: read+write. Group+Other: none | SSH private keys (~/.ssh/id_rsa) |
| 400 | r——– | Owner: read-only. Group+Other: none | Read-only backups, PEM files |
| 444 | r–r–r– | Everyone: read-only | World-readable static files |
| 4755 | rwsr-xr-x | 755 + Setuid: runs as file owner | System binaries (sudo, passwd, ping) |
| 2755 | rwxr-sr-x | 755 + Setgid: runs as file group | Group-shared executables |
| 1777 | rwxrwxrwt | 777 + Sticky: users can only delete own files | /tmp, /var/tmp directories |
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