Chmod 664 Explained
Chmod 664: owner and group can read and write, others can only read. Common for collaborative files on shared systems.
Permission
664
rw-rw-r--
chmod 664 filename
Permission Breakdown
| Role | Read (4) | Write (2) | Execute (1) | Octal | Meaning |
|---|---|---|---|---|---|
| Owner | r | w | - | 6 | read, write |
| Group | r | w | - | 6 | read, write |
| Others | r | - | - | 4 | read |
Visual Permission Grid
Detailed Explanation
The permission 664 allows the owner and group to read and write, while others can only read.
Octal breakdown:
- 6 (Owner): read (4) + write (2) = read and write
- 6 (Group): read (4) + write (2) = read and write
- 4 (Others): read (4) only
In symbolic notation this is rw-rw-r--. The owner and group members can view and modify the file. All other users can read but not modify it. Nobody can execute the file directly.
This permission is commonly the default for new files created on many Linux distributions (when umask is set to 002). It provides a good balance for collaborative environments: team members in the same group can edit files together, while the rest of the system can still read them. This is particularly useful for shared development projects and content management workflows.
Use Case
Default file permission on many Ubuntu and Fedora systems. Used for shared project files where team members (group) need to edit, but the file should be publicly readable.