Help : Unable to authenticate su

[Dreamerman]

No, that's a ******* thing. Just log-off and log back in

Hi again. I rebooted & still can't authenticate su. Result as below. Is there anything else I can try ? Thanks

master@ubuntu-server:~$ cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 ubuntu-server

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

[Dreamerman]

Hi again. I rebooted & still can't authenticate su. Result as below. Is there anything else I can try ? Thanks

master@ubuntu-server:~$ cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 ubuntu-server

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

This is another result. Still can't get into su.....sigh.....

master@ubuntu-server:~$ cat /etc/hostname
ubuntu-server

[caljohnsmith]

Did you try "sudo -i" again? Your original problem of it returning the error "sudo: unable to resolve host ubuntu-server" should be solved now that your host name is the same in /etc/hosts and /etc/hostname. That would at least give another clue about your problem.

[iaculallad]

Or maybe you're entering the wrong password when invoking the su command. Remember that using su should require you to input the root password w/c by default is disabled in Ubuntu. Try setting the password for su first:

sudo passwd root

[caljohnsmith]

Or maybe you're entering the wrong password when invoking the su command. Remember that using su should require you to input the root password w/c by default is disabled in Ubuntu. Try setting the password for su first:

sudo passwd root

That's a good point, but I think we should respect Ubuntu's philosopy about the root account not encourage Dreamerman to set the root password. If he needs to get a root shell, he really should do it with "sudo -i" and not "su".

[Dreamerman]

Did you try "sudo -i" again? Your original problem of it returning the error "sudo: unable to resolve host ubuntu-server" should be solved now that your host name is the same in /etc/hosts and /etc/hostname. That would at least give another clue about your problem.

Hi. Result as follows. Seems I can authenticate sudo but not su. Any ideas why ? Thanks

master@ubuntu-server:~$ sudo -i
[sudo] password for master:
root@ubuntu-server:~# exit
logout
master@ubuntu-server:~$ su
Password:
su: Authentication failure
master@ubuntu-server:~$

[iaculallad]

Try this to resolve your SU problem: Drop on your terminal:

sudo -i

and input your password. On your successful authentication, you should be dropped to the root terminal. Now, issue the command below:

chmod +s /bin/su

and exit on the root terminal:

exit

and test your su

su

[Dreamerman]

Try this to resolve your SU problem: Drop on your terminal:

sudo -i

and input your password. On your successful authentication, you should be dropped to the root terminal. Now, issue the command below:

chmod +s /bin/su

and exit on the root terminal:

exit

and test your su

su

Hi. Tried your approach but still the same.

master@ubuntu-server:~$ sudo -i
[sudo] password for master:
root@ubuntu-server:~# chmod +s /bin/su
root@ubuntu-server:~# exit
logout
master@ubuntu-server:~$ su
Password:
su: Authentication failure
master@ubuntu-server:~$

[iaculallad]

Try setting the root password and unset it afterwards:

sudo passwd

and input your password, then try running su

If that still fails, Unset the root password:

sudo passwd -l root

[Dreamerman]

Try setting the root password and unset it afterwards:

sudo passwd

and input your password, then try running su

If that still fails, Unset the root password:

sudo passwd -l root

*HAIL THE MASTER* Thank you so very much

master@ubuntu-server:~$ sudo passwd
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
master@ubuntu-server:~$ su
Password:
root@ubuntu-server:/home/master#