super user password

heli37 · 08-21-2012, 08:06 AM

Hi

Havent used my machine in ages and have forgotten the super user password. How can I find or alter it please?

Thanks

pixellany · 08-21-2012, 08:14 AM

Boot up from a Linux Live CD, mount the internal hard drive and edit the root entry in the /etc/password file to remove the first "x". The revised entry will look something like this:
root::0:0:root:/root:/bin/bash

You will now be able to boot into single-user mode and login as root with no password----then you can create new passwords as needed.

sundialsvcs · 08-21-2012, 08:18 AM

Quote:

Originally Posted by pixellany

Boot up from a Linux Live CD, mount the internal hard drive and edit the root entry in the /etc/password file to remove the first "x". The revised entry will look something like this:
root::0:0:root:/root:/bin/bash

You will now be able to boot into single-user mode and login as root with no password----then you can create new passwords as needed.

You might find that the live-CD can actually do it just with the passwd command, executed when you have booted the DVD and are therefore logged-on as root. It depends somewhat upon exactly which DVD you are using.

nittmann · 08-21-2012, 01:20 PM

deleted

ntubski · 08-21-2012, 02:34 PM

Quote:

Originally Posted by nittmann

please disregard the previous two [MODERATED] answsers.... here is how it goes
there is a bit more to it, a couple of steps

Hmm, it seems like your answer is just a really really detailed version of pixellany's. It would be useful to say what you think is wrong with the other answers.

And please don't use orange or other light colours like yellow, they're really hard to read.

KernelJay · 08-21-2012, 02:42 PM

If you don't have a password set on the bootloader, you may be able to boot into single user mode and run 'passwd' that way without the need for a live cd. Some systems will ask for the root password to boot into single user mode in which case you would need to access the file system through a live CD (or by mounting the hard drive using another system). The last time I checked, Red Hat based systems (i.e. including CentOS and Fedora) did not have this requirement. Booting into single user mode on these systems is just a matter of editing the boot line in grub and adding 'single' to the boot argument list. Here is a link to Red Hat with some details: https://access.redhat.com/knowledge/...booting-single

nittmann · 08-21-2012, 03:12 PM

deleted

ntubski · 08-21-2012, 03:59 PM

Quote:

Originally Posted by nittmann

taking away the 'x' from /etc/passwd prevents pam/shadow from working and the result is always a wrong password

Confirmed, furthermore calling passwd at that point puts the new password in /etc/passwd instead of /etc/shadow:

Code:

~$ su -
Password: 
root@localhost:~# vi /etc/passwd
root@localhost:~# grep root /etc/passwd
root::0:0:root:/root:/bin/bash
root@localhost:~# logout
~$ su -
Password: 
su: Authentication failure
~$ sudo su -
root@localhost:~# passwd
Enter new UNIX password: 
Retype new UNIX password: 
passwd: password updated successfully
root@localhost:~# grep root /etc/passwd
root:$6$tR9JDqAL$7c8DqmIgDPY4io6R4Ypbk/PuVGdaRD6t5dCSHgICmlAIAdOO.avOfdkhfYY9w3Axbu/6Vs7Pa3mkFei6gTTbU/:0:0:root:/root:/bin/bash

When we correct wrong information EVERYBODY wins, it's not a competition.

nittmann · 08-21-2012, 04:42 PM

deleted

unSpawn · 08-21-2012, 06:33 PM

@nittmann: you may expect us to be lenient towards new LQ members allowing them time to acclimatize but personal attacks and provocations are a direct violation of the LQ Rules you agreed to adhere to when you signed up. Please do not do that again.

pixellany · 08-23-2012, 02:52 AM

Quote:

Originally Posted by ntubski

Confirmed, furthermore calling passwd at that point puts the new password in /etc/passwd instead of /etc/shadow:

When we correct wrong information EVERYBODY wins, it's not a competition.

I just ran a test....

I created a new user normally. Then I used my method (remove the x) and--as expected--I could log in to the new user account with no password. I then assigned a new password, and the account was back to normal ("x" in /etc/passwd, etc.)

I've used this method for recovering from lost passwords many times.........

The implication is that some distros are set up differently????

Quantumstate · 08-23-2012, 09:45 AM

Some RedHats boot right into root in single mode, and some don't.

There is yet much better way to get root which works on all distros, but I'm sure unSpawn wouldn't want me saying it.

szboardstretcher · 08-23-2012, 09:51 AM

Add 'single' to the kernel boot parameter. itll boot into single user mode. then 'passwd root'

Edit:

Wasn't sure which distro we were talking about.

This will work on RedHat, Centos, Scientific Linux and Fedora.

Hope that helps.

Quantumstate · 08-23-2012, 10:24 AM

Well szboardstretcher, this only works on a few distros as I said, not ones which recognize this security hole.

unSpawn · 08-23-2012, 11:26 AM

//OT comments moved here so this thread can remain on topic from here on.