### Types of user:

  1. Root User - It is the super user which can run any command generally used for administration.
  2. System User - Users needed for system specific operation/components, like mysql user to run mysql.
  3. Normal User - Other users which are created by root and have limited access given to them.

### Atributes:

  1. User Type: Super user
  2. User Name: root
  3. User ID: 0
  4. Group ID: 0
  5. Home Directory: /root
  6. Shell: /bin/bash

### Important Files:

  1. /etc/passwd - Keeps user account and password information.
  2. /etc/shadow - Keeps the encrypted password of the corresponding account

### Creating a User:

	1. Add a user:
		 # usesradd ajeet
	2. Assign a password:
		 # passwd ajeet
	3. Create user with account expiry date:
		 # useradd -e 2018-04-01 xyz
	4. Create a user with specific user id
		 # useradd -u 5111 pqr
	5. Create a user with specific user id and group id
		 # useradd -u 6111 -g 711 foo
	6. Add user to Multiple groups
		 # user add -G dev,qa,prod
	7. Add user with comments:
		 # user add -c”Deverloper” bar
		 # tail -1 /etc/passwd
	8. Add user with home directory
		 # user add -d /home/myhome appychip
		 # tail -1 /etc/passwd

### Deleting a User:

	1. Deleting existing user:
		 # userdel ajeet
	2. Delete user forcefully, even if the user is logged in
		 # userdel -f xyz
	3. Delete user with home directory
		 # user del -r appychip

### Modify User Property:

	1. Changing home directory of a user:
		 # usermod -d /home/appychip
	2. Changing Primary group of a user:
		 # usermod -g dev ford
	3. Lock(-L) and Unlock(-U) users
		 # usermod -L  pqr
		 # usermod -U pqr
		 Verify in /etc/shadow if an ! mark is present in front of user name. If present then user is locked.
		 After unlock it will disappear
	4. Changing login name and password
		 # usermod -I xyz pqr
		 # usermod -p p@ssWord xyz
	5. View Account raging information:
		 # chage -I xyz
	6. Changing password parameters:
		 # chage xyz
		 Enter a new value