Chmod 000 Explained
Chmod 000 removes all permissions from a file. No user can read, write, or execute. Learn when this extreme permission makes sense.
Permission
000
---------
chmod 000 filename
Permission Breakdown
| Role | Read (4) | Write (2) | Execute (1) | Octal | Meaning |
|---|---|---|---|---|---|
| Owner | - | - | - | 0 | no permissions |
| Group | - | - | - | 0 | no permissions |
| Others | - | - | - | 0 | no permissions |
Visual Permission Grid
Detailed Explanation
The permission 000 removes all access from a file for everyone, including the owner.
Octal breakdown:
- 0 (Owner): no access
- 0 (Group): no access
- 0 (Others): no access
In symbolic notation this is ---------. No user can read, write, or execute the file through normal file operations. However, the root user (superuser) can still access the file regardless of permissions. The file owner can also change the permissions back using chmod since permission to change permissions is based on ownership, not the permission bits themselves.
This permission is rarely used in practice. It effectively locks a file away from all normal access. One use case is temporarily disabling access to a sensitive file without deleting it, or as a security measure during maintenance. Some administrators use 000 on files they want to ensure are not accidentally accessed by automated processes or cron jobs during system updates.
Use Case
Used to temporarily lock a file during maintenance, or as a placeholder permission that forces explicit permission setting before the file can be used.