When I run su or su root to get root privileges I get the following error message (regardless if I run su in a terminal window or directly on console):

sharon@obelix:~$ su
Password:
su: Authentication failure
Sorry.

sharon@obelix:~$ su root
Password:
su: Authentication failure
Sorry.

My root password works correctly on console. Su works correctly if I substitute to a different user from root. My Linux Distribution is Debian.

I think this might be a group problem so I also printed the group membership of the user I was when I tried to run su.


sharon@obelix:~$ groups
sharon dialout cdrom floppy sudo audio dip video users
sharon@obelix:~$

I appreciate your help.

ScS

Presuming things work the same, you probably have to have "wheel" group, as that's usually the one that controls the "su" command option(s).

regards

John

p.s. you could always see if you can get into root with suspaceminus i.e. su -

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Hi, after searching google and asking in IRC Freenode > #debian and having the same problem as you I thought that if I removed my username and my home directory after making a backup I could have a solution for "su" authentication failure. So, I created a directory called "Safe" in /home deleted my username and username directory and went to "System > administration > Users and Groups" and added me again there and recreated my home user. After that I issued "su" command again typed the passw and "voialà" it was a total success. Moved my files from Safe to my /home/me and had no more problem with "su". Perhaps, you can try this way :-)

I just came to this thread when i too faced the same problem
Now i think it's solved
i think following will help you

su passwd