⌨️ Ubuntu basics user account commands

As working with team as software developer, we have to create multiple users in linux. By default in cloud server provide ubuntu user by default but still sometime we need more user. Here I’m noting down set of commands used for creating user and updating password of users.

Create new user account on Ubuntu Linux

• To add a new user in Ubuntu run sudo adduser <NewUserName>.
• Enter password and other needed info to create a user account on Ubuntu server.
• New username would be added to /etc/passwd file, and encrypted password stored in the /etc/shadow file.
• Once the user is added, we can add it in sudo group with usermod -aG sudo userName.

Update password of any existing user account on Ubuntu

• Run command sudo passwd <userName>.
• To change the password of root user run, above command with userName as root.
• You can directly update the password of logged in user by passwd.

Delete user account

• Run command sudo userdel <userName>.
• To delete home directory and mail spool too, run sudo userdel -r <userName>.

Delete user account password:

• Run command passwd --delete <userName>.
• To verify that password is empty run grep -w '^UserNameHere' /etc/shadow, output should something like: realchoubey::19431:0:99999:7:::.
• Recommend to set user shell to nologin to avoid security related problems:usermod -s /usr/sbin/nologin <userName>

Screen:

Many times we need to run long running commands, as ssh shell timeout after certain time the process also breaks and tasks which we were looking to complete also breaks. To avoid that we can use Screen in linux. Below are the commands that can be used:

• Install command: sudo apt install screen
• Start screen with some name of screen: screen -S realchoubey-session
• To get out of screen session or in more technical term to detach from screen press Crtl+a+d use command screen -d realchoubey-session.
• Once you are out, run screen -ls to list all the screen running
• To reattach or resume screen session, we can use -r option. Command will look like screen -r realchoubey-session.
• Once your work is done don’t leave screen session, kill it with below command screen -XS realchoubey-session quit

Everywhere I have used name for session, but if you forget to give name to session then also you can do all above operations using PID, which can be get with

~$ screen -ls
There is a screen on:
21956.pts-0.ip-172–31–35–193 (04/23/23 07:35:39) (Detached)

21956 is the PID of session we can be used in place of session name, which is realchoubey-session in examples.