Visually build Unix file permissions. Toggle read, write, execute for owner, group, and others β get octal and symbolic notation instantly.
chmod 000 filename| Entity | r | w | x | Octal | Permissions |
| Owner | 0 | 0 | 0 | 0 | --- (none) |
| Group | 0 | 0 | 0 | 0 | --- (none) |
| Others | 0 | 0 | 0 | 0 | --- (none) |
| Octal | Symbolic | Binary | Description |
|---|---|---|---|
| 0 | --- | 000 | No permissions |
| 1 | --x | 001 | Execute only |
| 2 | -w- | 010 | Write only |
| 3 | -wx | 011 | Write + Execute |
| 4 | r-- | 100 | Read only |
| 5 | r-x | 101 | Read + Execute |
| 6 | rw- | 110 | Read + Write |
| 7 | rwx | 111 | Read + Write + Execute |
Ideal for web server directories: owner can write, others can only read and traverse.
chmod 755 means the owner has read (4), write (2), and execute (1) = 7; group has read and execute = 5; others have read and execute = 5. Common for web server directories.
Octal notation uses numbers (e.g., 755) where each digit encodes three permission bits. Symbolic notation uses letters (e.g., rwxr-xr-x) that are more human-readable.
Avoid chmod 777 in production β it allows any user to modify or delete the file. Use it only in development environments or for truly public temporary files.
Setuid (4xxx) makes executables run as the file owner. Setgid (2xxx) makes files inherit the group of the directory. Sticky bit (1xxx) on directories prevents users from deleting others's files (used on /tmp).