User Can't Login

[Qcheck]

When a linux user can't login, what is the first place to look into?

Please let me know, how to debug? This is just for an interview question.

Thank you.

[Zinky · Accepted solution]

Depending on how the Linux system is secured configured, the following are what you can as an admin check:

1.) Check if user has a login and if user is using that login
2.) Check HOW he is trying to Log in (telnet, ssh, etc)
3.) Check if he is allowed to login (restrictions to time, from where, etc)
4.) Check if his account is locked

[Qcheck]

Alzhy, Thank you for the response.

Do you mean the login of the user means, login shell? Which is in /etc/passwd?

Thank you

[Zinky]

By "login" - I mean a user account in the Linux system.

Note: a properly configured Linux System will not give the user a clue as to why it is unable to login except at times for the usual feedback like - expired password, login/user not exist, etc. (it really all depends on how the Linux system was configured/secured)

[Qcheck]

Thank you, Alzhy.

[Qcheck]

I thought more responses on this, but I don't have anymore, I would like to close the case.