chmod 444 explained (r--r--r--)

chmod 444 sets the permissions to r--r--r--.

• Owner: read
• Group: read
• Others: read

When to use it

Files that should be read-only for everyone, including the owner.

Security note

The owner can still change the mode back with chmod, so this prevents accidents, not malicious edits.

Tip: applying it to files and directories separately

Directories need the execute bit to be entered, files usually do not. Set them separately: find dir -type d -exec chmod 755 {} + and find dir -type f -exec chmod 644 {} +.

Other common modes