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User

Table of contents

Users

  • Logout as user: ctrl d
  • Change user: su - username
  • Change to root: su - root, or sudo -i
  • Set password for root: sudo passwd
  • Add user: adduser username, system will ask to enter password, enter x 2 for no password.
  • Get users and permission 
      usermod -aG sudo [user-name]
  users 
  ls -al

User in file

Add user www-data inside the nginx.config file is the same as running chmod -R www-data.

Password control

  1. Login as root
  2. Run vim /etc/sudoers or sudo visudo
  3. Add [user-name] ALL=(ALL) NOPASSWD:ALL to the last line of sudoers file

Change user-name 

sudo usermod -l [new-Username] [old-Username]

Permission with chown & chmod 

chown -R user:www-data /var/www/
  • chown: change Owner
  • user: the user
  • www-data: the group
  • /var/www/: the directory you want the user have the permission
chmod -R 777 /var/www
  • to give the user ALL for the directory of /var/www
  • Example folders
chmod -R 750 /var/www/example.com
chmod -R 755 /var/www/example.com/wp-content
chmod -R 777 /var/www/html/wp-content/

Delete user

  • To delete user
deluser username

List user 

cut -d: -f1 /etc/passwd
less /etc/passwd

Linux User Permission logics 

R - read - 4 bits, read it 
W - write - 2 bits, write / modify it
X - execute - file 1 bit, execute it 

u - the owner user
g - the owner group
o - others (neither u, nor g)
a - all users

Permission chart

Triplet for u (owner user): rwx => 4 + 2 + 1 = 7
Triplet for g (owner group): r-x => 4 + 0 + 1 = 5
Triplet for o (neither u, nor g): r-x => 4 + 0 + 1 = 5

Example

-rwx r-x r-x (755) => - rwx r-x r-x => - (- is file, d is directory), rwx (owner user) = 7, r-x (group) = 5, r-x (other user) = 5

Change permission chmod 

ls -l
   # output to see permission 
chmod +x [path-to/file1] 
   # all user gets `+x`  
chmod u+x [path-to/file1]
   # owner user gets `+x`
chmod g+x [path-to/file1]
   # group gets `+x`
chmod o+x [path-to/file1]
   # other gets `+x`