Linux permissions decide who can do what to every file. Once the rwx model clicks, the cryptic -rwxr-xr-- makes perfect sense.
Reading the bits
-rwxr-xr-- owner=rwx group=r-x other=r--
│└┬┘└┬┘└┬┘
│ │ │ └ other (everyone else)
│ │ └ group
│ └ owner (user)
└ type (- file, d dir, l link)Each of the three classes gets read, write, execute.
Changing them
chmod 640 file # owner rw, group r, other none
chmod +x script.sh # make executable
chown user:group file # change ownershipNumeric: r=4, w=2, x=1, summed per class. 640 = rw- r-- ---.
On directories, x means "enter"
| On a file | On a directory |
|---|---|
| r = read contents | r = list names |
| w = modify | w = add/remove files |
| x = run it | x = cd into / access |
A directory without
xcan't be entered even if readable — a common "permission denied" head-scratcher.
Security: keep secrets
600/640and owned tightly — exactly how the wiki's config is locked down.
Related: Secrets Management · Linux Server Hardening Baseline · Understanding systemd