The Permission Model
Read, Write, Execute
Every file has permissions for three classes: user (owner), group, other.
-rwxr-x r-- 1 alice devs 4096 file
│└┬┘└┬┘└┬┘
│ u g o
└ type (- file, d dir, l link)| Symbol | Octal | File meaning | Directory meaning |
|---|---|---|---|
| r | 4 | read contents | list entries |
| w | 2 | modify contents | create/delete entries |
| x | 1 | execute | enter (cd into) |
Common octal modes: 755 (rwxr-xr-x), 644 (rw-r--r--), 700 (rwx------), 600 (rw-------).
| Command | Action |
|---|---|
chmod 640 file | Set octal permissions |
chmod u+x,g-w file | Symbolic change |
chown alice:devs file | Change owner + group |
chgrp devs file | Change group only |
chmod -R | Recurse into directories |
$ chmod 640 report.txt && ls -l report.txt
-rw-r----- 1 alice devs 0 Jan 1 10:00 report.txt