tool::chmod-detail
chmod 444
r--r--r--
Read-Only for Everyone
Permission Structure
Owner (User)
✓Read (r)
✗Write (w)
✗Execute (x)
Group
✓Read (r)
✗Write (w)
✗Execute (x)
Others
✓Read (r)
✗Write (w)
✗Execute (x)
Octal
444Symbolic
r--r--r--Explanation
chmod 444 grants read-only access to owner, group, and others while blocking all writes and executions. Used for shared reference files that must not change, immutable configuration, or legal documents. Even root cannot modify the file without first running chmod, providing strong integrity guarantees.
Common Use Cases
- ▸Immutable shared license and legal documents
- ▸Release checksum/hash files (SHA256SUMS, etc.)
- ▸Immutable shared reference data files
- ▸Checksum files for deployed binaries
- ▸Read-only public configuration templates
Security Considerations
444 effectively protects file integrity, but root can still override it via chmod. For true immutability, add the immutable attribute with chattr +i. Applying 444 to web server configuration files prevents a web shell from overwriting them, even if one is uploaded.
Command Examples
$ chmod 444 LICENSE SHA256SUMS$ chmod 444 /etc/hosts # prevent modification$ chattr +i /etc/hosts # fully immutable (root cannot modify)$ find /opt/releases -type f -exec chmod 444 {} \;Related Permissions
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