chmod & chown

chmod — symbolic mode

Add or remove permissions with +/- on u (user), g (group), o (other), a (all).

chmod u+x deploy.sh    # owner can execute
chmod go-w notes.txt    # group & other lose write

chmod — numeric mode

r=4, w=2, x=1 — sum them per triplet. 755 = rwxr-xr-x, 644 = rw-r--r--.

chmod 755 deploy.sh     # owner: rwx, group/other: r-x
chmod 644 notes.txt     # owner: rw-, group/other: r--

chown — change ownership

chown changes a file's owner and/or group; usually needs sudo.

sudo chown alice deploy.sh
sudo chown alice:devs deploy.sh

Quick check: What does `chmod 644 file` set?

• rwxrwxrwx
• rw-r--r--
• r--r--r--