Permissions and owners

The chmod command

Changes the permissions of a file or folder. The basis of Linux security.

Syntax

chmod <modo> <archivo>

Most useful options

755Everything for the owner; read and execute for the rest
644The owner reads and writes; the rest only reads
+xAdds execute permission
u+w o-rSymbolic mode by groups: u, g, o

Copy-ready examples

$ touch run.sh && chmod 755 run.shScript executable by everyone
$ touch run.sh && chmod +x run.shThe minimum: make it executable
$ touch secreto.txt && chmod 600 secreto.txtOnly the owner can read and write it

You can try them in the browser terminal: it does not touch your computer.

Typical mistakes

  • Only the owner of the file (or root) can change its permissions.

Related commands

chownumaskls

FAQ

What does 755 mean?

4+2+1 for the owner, 4+1 for group and others: read and execute.

Why Permission denied when running my script?

It lacks execute permission: chmod +x.

Learn to actually use it

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