chmod 400
chmod 400 gives r--------. Read-only for the owner. Used for private keys and secrets that should never change, such as an AWS .pem file.
- Free
- No Sign-Up
- Runs in Your Browser
Owner
Group
Others
Permissions
r--------
Command
chmod 400 file
Chmod Calculator
chmod 400 explained
Octal400
Symbolicr--------
Ownerread
Groupno access
Othersno access
ls -l Shows-r--------
Commandchmod 400 file
Symbolic Commandchmod u=r,g=,o= file
Each digit of 400 is one class of user and adds up read (4), write (2) and execute (1). 4 for the owner is read; 0 for the group is no access; 0 for the others is no access.
Read-only for the owner. Used for private keys and secrets that should never change, such as an AWS .pem file.
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 400 mean?
Owner: read. Group: no access. Others: no access. In letters: r--------.
Is chmod 400 safe?
Yes, for the uses described here. Nobody outside the classes given write access can change the file.
How do I apply 400 to every directory but not files?
find /path -type d -exec chmod 400 {} + (and use -type f for files only).
How do I set 400 recursively?
chmod -R 400 /path. Be careful: this gives files and directories the same mode, which is rarely what you want; the find command above is safer.
Free Tools
More tools
Chmod CalculatorLinux file permissions in octal and symbolic form, both ways.Cron Expression GeneratorBuild a crontab schedule and see it in plain English with next run times.Firewall Rule GeneratorGenerate iptables, nftables and UFW rules for common server set-ups.Subnet CalculatorNetwork, broadcast, usable range and mask for any IPv4 or IPv6 CIDR.
Run servers for other people?
Frabs stops the abuse their VMs send out, and keeps your network off blocklists.