Chmod 400 Linux Permissions (r--------)
chmod 400 sets permissions to r--------: Owner: Read only (4), Group: No access (0), Others: No access (0). File is protected against accidental modifications by anyone, including the owner. Read access is exclusive to owner.
Read only
No access
No access
Security Notice
Recommended for cloud certificates (.pem files), SSL private certs, and immutable read-only keys.
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Linux Permissions Breakdown
| Octal | Symbolic | Purpose |
|---|---|---|
| 755 | rwxr-xr-x | Standard for directories and scripts |
| 644 | rw-r--r-- | Standard for regular files |
| 777 | rwxrwxrwx | Full permissions for everyone (insecure) |
| 700 | rwx------ | Private owner directory |
| 600 | rw------- | Private secret file |
| 666 | rw-rw-rw- | Read and write for all |
| 400 | r-------- | Read-only for owner |
FAQ
How do I set permissions to 400 in Linux?
Run the command: chmod 400 <filename>. For directories and their contents recursively, run: chmod -R 400 <directory>.
Is chmod 400 secure?
Recommended for cloud certificates (.pem files), SSL private certs, and immutable read-only keys.
What does the symbolic code r-------- represent?
The 9 characters represent 3 triplets: Owner (r--), Group (---), and Others (---). 'r' is read (4), 'w' is write (2), 'x' is execute (1), and '-' is disabled (0).