chmod 440
chmod 440 gives r--r-----. Read-only for the owner and group. The standard mode for /etc/sudoers.
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Owner
Group
Others
Permissions
r--r-----
Command
chmod 440 file
Chmod Calculator
chmod 440 explained
Octal440
Symbolicr--r-----
Ownerread
Groupread
Othersno access
ls -l Shows-r--r-----
Commandchmod 440 file
Symbolic Commandchmod u=r,g=r,o= file
Each digit of 440 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; 0 for the others is no access.
Read-only for the owner and group. The standard mode for /etc/sudoers.
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 440 mean?
Owner: read. Group: read. Others: no access. In letters: r--r-----.
Is chmod 440 safe?
Yes, for the uses described here. Nobody outside the classes given write access can change the file.
How do I apply 440 to every directory but not files?
find /path -type d -exec chmod 440 {} + (and use -type f for files only).
How do I set 440 recursively?
chmod -R 440 /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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