chmod 400 — r--------

What chmod 400 allows, when to use it, and the calculator pre-filled with it — toggle any box to compare.

400
r--------
Owner4
r--
Group0
---
Others0
---
Special bits
chmod 400 filename
chmod -R 400 /path/to/dir

What this means

Owner can read. Group has no permissions. Others has no permissions.

What chmod 400 allows

WhoReadWriteExecute
Owner✓——
Group———
Others———

Read-only for the owner and nothing for anyone else — AWS .pem key files need this (or 600), otherwise ssh complains about an unprotected private key.

Commands

chmod 400 fileset it on one file or directory
chmod u=r,g=,o= filethe same thing in symbolic form
chmod -R 400 dir/recursively — careful: it applies to files and directories alike
ls -l filecheck the result: -r-------- (a directory shows dr--------)

On a directory, read lets you list it, write lets you create and delete entries, and execute lets you enter it and open what's inside. That's why directories usually get 755 or 750 while files get 644 or 640.

Frequently asked

What does chmod 400 mean?

Owner: read. Group: no access. Others: no access. In ls -l it shows as r--------.

What is the symbolic form of chmod 400?

chmod u=r,g=,o= file — it sets exactly the same permissions as chmod 400.

← Chmod calculator

Common chmod permissions explained

chmod 755rwxr-xr-xchmod 644rw-r--r--chmod 777rwxrwxrwxchmod 600rw-------chmod 700rwx------chmod 775rwxrwxr-xchmod 664rw-rw-r--chmod 400r--------chmod 444r--r--r--chmod 750rwxr-x---chmod 640rw-r-----chmod 660rw-rw----chmod 770rwxrwx---chmod 666rw-rw-rw-chmod 711rwx--x--xchmod 500r-x------chmod 550r-xr-x---chmod 555r-xr-xr-xchmod 440r--r-----chmod 740rwxr-----chmod 760rwxrw----chmod 1777rwxrwxrwtchmod 2755rwxr-sr-xchmod 2775rwxrwsr-xchmod 4755rwsr-xr-x
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