User and User Group

 

Below are the default UID and shell for users in RHEL-7

User	UID	Shell
Admin	0	/bin/bash
System	1-999	/bin/nologin
Regular	1000 +	/bin/bash

 

• Whenever a user is created be default it belongs to its own group.
• At creation, new user gets its default directories and files from /etc/skel
• Default password length, expiry, GID, UID range etc. is stored in /etc/login.defs
• /etc/passwd (user information, UID etc)
• /etc/group (group information, GID, associated user etc.)
• /etc/shadow (User password, expiry etc.)

 

• To add/edit new user & group

# adduser <user>

# useradd <user>

# useradd -g <group> <user>                    //force use GROUP as new primary group

# useradd -u <UID> <user>                       //Add user with specific unique UID

# groupadd <group>

# usermod -aG <group1>,<group2>,<group3> <user>         //to assign multiple group to user

# usermod -G ‘ ’ <user>                  //remove all group

# usermod -s <shell> <user>                     //to change shell

# gpasswd -a <user> <group>                   //add user in new group without removing from other.

# chage -l                                          //view user details from /etc/shadow

# chage -m                                        //modify user days etc.