chmod 444
chmod 444 gives r--r--r--. Read-only for everyone. Protects a file from accidental changes (the owner can still chmod it back).
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Owner
Group
Others
Permissions
r--r--r--
Command
chmod 444 file
Chmod Calculator
chmod 444 explained
Octal444
Symbolicr--r--r--
Ownerread
Groupread
Othersread
ls -l Shows-r--r--r--
Commandchmod 444 file
Symbolic Commandchmod u=r,g=r,o=r file
Each digit of 444 is one class of user and adds up read (4), write (2) and execute (1). 4 for the owner is read; 4 for the group is read; 4 for the others is read.
Read-only for everyone. Protects a file from accidental changes (the owner can still chmod it back).
On a directory, execute means permission to enter it and reach files inside; read means permission to list it. That is why directories usually have execute wherever they have read.
Questions
What does chmod 444 mean?
Owner: read. Group: read. Others: read. In letters: r--r--r--.
Is chmod 444 safe?
Yes, for the uses described here. Nobody outside the classes given write access can change the file.
How do I apply 444 to every directory but not files?
find /path -type d -exec chmod 444 {} + (and use -type f for files only).
How do I set 444 recursively?
chmod -R 444 /path. Be careful: this gives files and directories the same mode, which is rarely what you want; the find command above is safer.
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