User Management

I. Important files

/etc/passwd : contain user information
structure: username:passwd:UID:GID:description:homedir:shell
shell : /sbin/nologin (users cant log in system)

/etc/group : contain group information
structure: groupname:passwd:GID:usersList(users on secondary group)

/etc/shadow : contain password information
structure: username:password::::::::

II. Group management
1. Create group:
#groupadd

2. Edit group information:
#groupmod [option]

3. Delete group:
#groupdel

III. Users management
1. Create user:
#useradd [option]
->create a password : #passwd
example: #useradd -g hocvien -G adm -c "hoc vien 2" -d /data/hv2 -s /sbin/sh -m hv2

2. Edit user information:
#usermod [option]

Lock user: #passwd -l | #usermod -L
Unclock user: #passwd -u | #usermod -U
View user information: #id
View group that user belong to: #groups
Default file for creating user:
/etc/login.defs
/etc/default/useradd

3. Delete user:
#userdel [option]