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I just installed Ubuntu on a new machine and everything seemed to be going fine. I and a coworker were having some issues with a few things and have managed to lock-out a local admin (sudo?) account after unjoining an AD domain using realm while troubleshooting some McAfee issues were were having. I'm 99.9% certain that the password has not changed for the user. I have followed ALL the steps found here for resetting the password as root in recovery. When I try to run

sudo passwd USERNAME

I get the error:

root@hostname:~# sudo passwd USERNAME passwd:Permission denied passwd:password unchanged root@hostname:~#

When I try to do the steps for the "The Drastic Measures", I notice that the shadow file does not show what would usually indicate an encrypted password for the user. Instead it looks like:

username:!:14920:0:99999:7:::

I have removed the exclamation point and still have issues. Even when I run

passwd

as root through recovery, I get a permissions denied error. As it stands right now, I can only log into the machine as root through recovery. I'm at a complete loss at this point and trying to avoid breaking down the machine and starting from scratch. Any help you guys can provide would be greatly appreciated.

  • My guess is you have to remount your root file system rw . Also you do not need to run sudo as you are already root. Last USERNAME is not the same as username and neither is likely your actual username. – Panther Nov 21 '16 at 20:08
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    Possible duplicate of How do I reset a lost administrative password? – Panther Nov 21 '16 at 20:09
  • I made sure to run the mount -o remount,rw / before going through the steps in the link I posted. I still had those issues. BTW, username is def. not a real username. I'm working on a "govt" system so changed it to protect the innocent. – ProAm500 Nov 21 '16 at 20:28
  • If it is a "govt" system, I would expect it to use some kind of non-local password management such as ldap – steeldriver Nov 22 '16 at 0:16
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Sol:

vi /etc/pam.d/common-password
password        [success=3 default=ignore]      
pam_unix.so obscure sha512

=> Change it to "success=2"

Smile!

| improve this answer | |
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    What does this change do? – PerlDuck Nov 19 '18 at 11:18
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    @PerlDuck It changes the number modules to skip if password succeeds from 3 to 2. (source) This seems like a pretty niche solution, because by default it should be 2 unless someone's gone and messed it up. – Nonny Moose Dec 20 '18 at 2:21

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