Interview Questions on Linux User Management with Answers

1. How can you create a user without useradd command

Follow the below link
How to create a user without useradd command?

 

2. What is the default permission on user’s home directory?

700

 

3. What is the difference between .bash_profile and .bashrc?

Every time you login to a Linux (Red Hat) machine .bash_profile file is executed but In case you are already logged in and you open a new terminal then .bashrc file is executed

 

4. What is the command to create a user with a pre defined uid, shell and home directory?

useradd -m -d /path/to/home -s /bin/bash -u 550 <USER>

 

5. Explain each field of /etc/passwd

deepak:x:512:512:User:/home/deepak:/bin/bash
  • 1st field: username
  • 2nd field: x tells that an encrypted password is stored in /etc/shadow
  • 3rd field: uid
  • 4th field: gid
  • 5th field: Description
  • 6th field: home directory
  • 7th field: default login shell

 

6. How to change primary group for any user?

usermod -g <groupname>  <username>

 

7. If I delete a user, does it’s home directory gets deleted? If not then what is the command to delete the home directory of user along with the user

No.

# userdel -r <username>

 

8. Name any 3 files which are automatically created inside any user’s home directory when a user is added

.bashrc
.bash_profile
.bash_history

 

9. What is the command to view all the currently logged in users?

w

 

10. What is the command to change and view the expiry date for any user?

chage

 

11. What are the details you get with finger command?

Login Details
Mail
Home directory
Last login

 

12. How can you give a normal user all the root level privileges?

Add the user to wheel group and uncomment the wheel group line in sudoers file
Give the user all command permission in sudoers
How to give normal user root privileges using sudo in Linux/Unix

 

13. Name any 3 groups of which root is a member by default

root
bin
daemon
sys
adm
disk
wheel

 

14. How can you give sudo access to any user without asking him to provide passord every time he runs a command?

Add an extra parameter NOPASSWD in sudoers file while giving the user permission to run root level commands

 

15. Why do we use visudo rather than editing the file with vi or any other editor?

Follow this link
A guide on visudo and its usage

11 thoughts on “Interview Questions on Linux User Management with Answers”

  1. Default umask for the Root is 0022 hence file – 644 and dir – 755 whereas default umask for non-root user is 0002 hence file- 664 and dir -775 permissions.

    Reply
  2. Default Umask of Root is 0022 hence file – 644 and dir – 755 whereas default umask for non-root is 0002 hence file – 664 and dir – 775 .

    Reply
  3. Hi Shubham
    you can lock and unlock if you had two users have with same uid and gid also by using below commands .
    ex: i have two users test and test1

    usermod -L test –>it will lock to test user
    usermod -L test1 –> it will lock to test1 user

    u can verify in /etc/shadow file
    cat /etc/shadow |grep -i test
    cat /etc/shadow |grep -i test1

    o/p : u can observer below 2 lines after test: ! is there its indicates user is currently locked.
    test:!$6$mC7ZaS/G$4qD3TYhqujmS628mlYG1XcL3TxYYiWBeCMs9TM/.EfJ31RzedqOMQ0SCk3A3NPM7/rmHvNRdU5KmIkWwlZ96J1:17347:0:99999:7:::
    test1:!$6$2Z1S8yPW$dnLx0qwxBQOI9c9vjzJsD2IxXB7s2zuy3u4RhrJwjPWMCf7.rHIRBjZ9JgmsLx/VyPs3Rb7zKTQZoAHpoBgAO0:17347::::::

    Reply
  4. I have written this article to understand login process
    golinuxhub.com/2014/09/how-does-successful-or-failed-login.html

    but to troubleshoot login issues there are various things which can be done

    Like execute ssh with verbose and check the stage where it fails
    monitor the client node's sshd logs and see the error message you get (this will give you the best hint)
    Disable firewall on server and client side and see if that is the problem
    Minimize sshd hardening if any of your recent sshd hardening changes led to the problem
    check password of the usr, if it is blocked

    and many more..

    Reply

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