Management of permissions and users

ls -l -> shows file permissions 

$ ls -l
drwxr-xr-x 1 Piotr 197609   0 Jul  9 16:43 'a.txt'

The permissions are shown in the first block of the result. In the example above it would be drwxr-xr-x.

Permissions can be separated as follows:

F/---/---/---
-: dir/link/file
---: owner (me) permissions
---: group permissions
---: everyone's permissions

Mode type

Permissions types:

• r-– -> read permission

• rw- -> read and write permission

• rwx -> read, write and execute permission

Permissions have numeric values:

• r = 4

• w = 2

• x = 1

Owner	Group	World
rwx	r-x	r-x
1 1 1	1 0 1	1 0 1

Octal mode

Octal	Binary	Permissions
0	000	---
1	001	--x
2	010	-w-
3	011	-wx
4	100	r--
5	101	r-x
6	110	rw-
7	111	rwx

Owner	Group	World
rwx	r-x	r-x
1 1 1	1 0 1	1 0 1
7	5	5

Symbolic mode

Symbol	Meaning
u	only for the user
g	only for the group
o	only for all others (it's the world)
a	applies to everyone

chmod 755 myText             -> changes file permissions to 755
chmod u-r myText             -> removes file read permission
chmod u = rwx, go = r myText -> adds read, write, and run permissions to the user and only read to the group and others
id                           -> shows user ID
whoami                       -> shows name of logged in user
your userName                -> changes user
sudo command                 -> runs a command as superuser

To grant permissions we must give it a number that is the sum of each of these three letters:

---: 0
--x: 1
-r-: 2
-wx: 3
r--: 4
r-x: 5
rw-: 6
rwx: 7

To assign the permissions, the number must be given for both the owner, the group and the public.

---/---/---
666: rw-rw-rw-
750: rwxr-x---`

Change permissions

chmod [number] <file> -> allows you to change the permissions to a file

$ chmod 750 file.txt

Run as super user

sudo [script/command] -> run a command as super user