su root authentication failure
 

as a user added to the wheel group in gentoo linux I try 'su root' it asks me for a password I enter the correct password (I can doa root login fine, su is only problem) it gives me the error:

su: Authentication failue
sorry


the user in question has been added to the wheel group

I had a similar problem, the difference being that I tried to assign the /bin/su file to the group wheel after creating the group.
Check and see if /bin/su has the suid bit set.
Hope this will solve your problem.

thanx, chmod +s /bin/su fixed it.

Apparently `su' didn't have setuid bit set.

Run as root:

chmod +s /bin/su

and su should work better.

authentication failure for su
 

When I run su I get an error message "authentication failure". I then run
"chmod +s /bin/su" and I get an error message saying that

chmod: changing permissions of 'bin/su': Operation not permitted

Apparently su like most of my files are locked because of the system crash that I am trying to repair. Any suggestions how to unlock or find password for su?

have u tried to "sudo -i" first, then enter "chmod +s /bin/su"

Thanks Man Very Much .... sudo -i command save my day ......thanks again...

I have the same problem, but then when I run sudo -i I get "sudo: must be setuid root". How can I go around it. I can't get too the root to change sudo ^^

you have to login as root and set chmod +s /bin/su and /bin/sudo

Hey thanks. I wish I could log as root, but I can't. I even tried this http://www.psychocats.net/ubuntu/fixsudo but did not work. I will backup and reinstall. If I try sudo -i, then I get "sudo: must be setuid root", if I run su, then I get "su: Authentication failue". I logged in the repair mode (as root) and run chmod +s /bin/su, did not work either. Somehow I messed up sudoers/sudo badly.