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Before I mention anything further, DO NOT give me a response saying that terminal won't show password input. I'm AWARE of that.

I'm typing my user password in (not a capslock issue), and for some reason it still says 'Authentication Failure'.

Is there some other password (one I'm not aware of) I'm supposed to be using other than my user password? I've had this ubuntu before, on another hard drive and I didn't have this problem. (And it was the same ubuntu, ubuntu 12.04 LTS)

ai@AiNekoYokai:~$ groups
ai adm cdrom sudo dip plugdev lpadmin sambashare
ai@AiNekoYokai:~$ lsb_release -rd
Description:    Ubuntu 12.04 LTS
Release:    12.04
ai@AiNekoYokai:~$ pkexec cat /etc/sudoers
# This file MUST be edited with the 'visudo' command as root.
# Please consider adding local content in /etc/sudoers.d/ instead of
# directly modifying this file.
# See the man page for details on how to write a sudoers file.
Defaults    env_reset
Defaults    secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

# Host alias specification

# User alias specification

# Cmnd alias specification

# User privilege specification
root    ALL=(ALL:ALL) ALL

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL

# See sudoers(5) for more information on "#include" directives:

#includedir /etc/sudoers.d

I can log in with my password, but it's not accepted as valid for authentication <-- That is pretty much my issue. (Although, I haven't gone into recovery mode.)

I've ran:

ai@AiNekoYokai:~$ ls /etc/sudoers.d

And also reinstalled sudo with:

pkexec apt-get update
pkexec apt-get --purge --reinstall install sudo

pkexec usermod -a -G admin $USER <- Says admin does not exist

su $USER <- worked for me, however, my password still does not do much (in sense of not working for other things)

I changed my password with pkexec passwd $USER. I was able to change it no problem.

gksudo xclock was something I was able to get into, no problem. (Clock showed)

ai@AiNekoYokai:~$ gksudo xclock
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3 Answers 3

I had this problem when I was using a special keyboard layout (Bépo). The terminal was not recognizing the special characters. Maybe this is your problem too ?

How to change the keyboard-layout in the console, with special characters?

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I appreciate you trying to help, but I don't have a special keyboard layout. But I do thank you very much for the effort! ^-^ –  Souta Jun 18 '12 at 23:56
This did it for me (Lubuntu install) when I was using "English - English(US, international with dead keys)" and switched to "English - English (US)". –  Blue Ice Aug 25 '14 at 21:02
up vote 3 down vote accepted

Run pkexec passwd $USER to change password. Then retry.

If it doesn't work, there are other troubleshooting things you can do (detailed in the question above).

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Are you saying that pkexec passwd $USER worked for you? I'd gotten the sense that it did not, and that the problem was instead because of some typo you'd been making (something like using su instead of sudo, but not necessarily that). –  Eliah Kagan Jun 21 '12 at 2:53
It was part of both. I kept typing something wrong (unsure what it was) but then on the last time I tried it, I managed to get it working. I honestly think it was mostly a password issue. I was using some special characters (not umlaut-special), and a friend of mine pointed out something to me with how my previous password started and how the terminal might have mistook said password. (That, or it was just some freaky glitch, but since it hasn't happened since password change, I'm calling user error on myself.) –  Souta Jun 21 '12 at 13:42
@mods then this really should not be the accepted answer –  don.joey Mar 8 '13 at 7:35

Why dont you add (to be more explicit)

# User privilege specification
root    ALL=(ALL:ALL) ALL  
ai      ALL=(ALL:ALL) ALL
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protected by Community Apr 11 '14 at 18:29

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