I using Redhat linux. I am trying to run the following command and would like to know why it is not prompting for password?

Here is what I am doing. I open the terminal window and enter my username and password. After that I run the following command

sudo su - anotherusername

The command runs successfully without prompting for password of anotherusername. I want to know why I don't get password prompt?

Are there any circumstances where I will get password prompt for anotherusername?

Or Is there a different command that will prompt me for anotherusername password?

I mistakenly posted this question in StackOverflow https://stackoverflow.com/questions/46632690/sudo-su-username-not-prompting-for-password and I was told that if my username is part of sudoers group then I will not get password prompt.

Just want to confirm if that is the only reason or there are other reasons as well for not receiving password prompt.


sudo su runs su as root; thus there is no need for su to ask a password.

The question might be why sudo does not ask for a password (the invoking user's or root's). The output of sudo -l may explain that. Or sudo has been invoked before and considers the formerly entered password still valid.


Try searching for the username of the user running the sudo command in /etc/sudoers:

$ sudo grep yourusername /etc/sudoers
yourusername    ALL=(ALL)       NOPASSWD: ALL

If the output of that grep command contains NOPASSWD:, then use the visudo command to edit and remove the NOPASSWD: from that line.

Also, you'll be prompted for the password of the user running the sudo command, not the password of the account that you're trying to login to.

  • sudo -iu anotherusername would be somewhat easier, though
    – roaima
    Oct 8 '17 at 20:56

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