1 - Managening users and groups.md

Managening users and groups

Creating an user

$ sudo useradd -m <login>

-m option creates a home for it.

Removing an user

$ sudo userdel -r <login>

-r option removes his home.

Checking if group already exists

$ grep -PHnro '^<group_name>(?=:)' /etc/group

Listing groups of an user

$ groups <user_name>

Creating a group

$ sudo addgroup <group_name>

Removing a group

$ sudo groupdel <group_name>

Putting an user in a group

$ sudo adduser <existent_user> <existent_group>

Removing an user from a group

$ sudo deluser <user> <group>

Note: Needs restart to make effect.

2 - permissions.md

Change Permissions of File

$ sudo chmod [permission_numbers] <folder_or_file>

When you change permissions on folder, you can to use -R parameter (recursivity).

Permissions table

-----------------------
 number    permissions
-----------------------
   7           rwx (4 + 2 + 1)
   6           rw- (4 + 2)
   5           r-x (4 + 1)
   4           r--
   3           -wx (2 + 1)
   2           -w-
   1           --x
   0           ---
-----------------------

Subtitle of Numbers

• 1 and 3: not open by folder browser (-r)
• 4 and 6: open by folder browser but not by command line (-x)

Subtitle of Permissions

• r: access folder but don't list its content
• x: run file (requires access permission for all parent folder)
• w: write on file or folder (requires run permission for all parent folder)

Listing Permissions

$ ls -l <folder_name>

Obs.: May require "sudo".

Change Owner of File or Folder

$ sudo chown <user>:<group> -R <file_or_folder>