What are user, group, and other in Linux permissions?
Every file carries three separate permission sets — one for the owning user (u), one for the owning group (g), one for everyone else (other/o) — and you are judged by exactly ONE of them, not a combination.
The non-obvious rule is that the kernel picks the first matching class and stops: if you're the owner, only the u bits apply even if the g or o bits are more generous. This is why an owner can deliberately have less access than strangers (e.g. -rw----rw-), and why you should grant access through the group, never through other.
| Category | Symbol | Description |
|---|---|---|
| User | u | The file's owner |
| Group | g | Members of the file's group |
| Other | o | Everyone else |
Permission evaluation (first match wins):
- Are you the owner? → Use user permissions
- Are you in the group? → Use group permissions
- Neither? → Use other permissions
Example:
-rw-r----- labstudent developers file.txt
- Owner (labstudent): read + write
- Group (developers): read only
- Others: no access
Important insights:
- You only get ONE set of permissions
- If you're the owner, group permissions don't apply to you
- There is NO permission inheritance from parent directories
- Root bypasses all permission checks
Tip: Don't rely on "other" permissions for access control - use groups instead for better security.