User & Group Management : Commands and Concepts

Linux user in short

• Root User: The admin with full control over the system.

• Regular Users: Everyday users with limited permissions.

• System Users: Special users for running background services.

Commands for User Creation and Management

1. Create a User:

• • Command: sudo adduser username

    • Example: sudo adduser devops_user

    • What it does: Creates a new user named "devops_user" and sets up their home directory

2. Add User to a Group:

• Command: sudo usermod -aG groupname username

• Example: sudo usermod -aG devops_team devops_user

• What it does: Adds the user "devops_user" to the "devops_team" group.

  3. Set Password and grant sudo access

• command: sudo passwd devops_user or passwd -e devops_user

• sudo usermod -aG sudo devops_user

Command to create a group in Linux:

• command: sudo groupadd groupname

• example sudo groupadd devops_teams

Restricting SSH login for certain users in /etc/ssh/sshd_config

To Perform this operation in Linux you need to first install sshd using command

• After installation is complete you can use command to restrict the specific user for SSH login

/# This command is used to open the sshd_config file using sudo access in vim editor to modify user permission in a SSH

Once you edit the vim editor reach to the end of lines in editor and use command

example: DenyUsers devops_user1.

You can also restrict multiple users by adding their username following space.