Command library / chmod

Change file permissions

Changes who may read (r), write (w) or execute (x) a file. Permissions are set for three audiences: the owner (u), the group (g) and everyone else (o). In octal mode each audience is one digit — r=4, w=2, x=1 added together — so 755 means rwx for the owner and r-x for the group and others.

Usage

Options and flags

• mode

  octal (755) or symbolic (u+x) permission change

• file

  file or directory to change

• -R

  recursive: apply to a directory and everything inside it

• -v

  verbose: print every file that is changed

Examples

• chmod 755 backup.sh

  Owner rwx, everyone else r-x — a normal executable script.

• chmod u+x deploy.sh

  Add execute for the owner only; leave other bits untouched.

• chmod 600 ~/.ssh/id_rsa

  Private keys must be readable and writable by the owner only.

• chmod -R 750 /opt/tools

  Owner rwx, group r-x, others nothing — for a whole tree.

Common mistakes

Related commands