Forgot my root password and can't login

[marlonmin]

How can I reset my root password? I can't remember. I haven't used the computer for a while, and can't remember other passwords as well.

I tried to login with grub, but didn't find a way to log with grub.

Thanks for help,

[SpecialEd]

One way is to log in with a "live" version then edit your user/password.

A simple web search turns up many help pages:

http://www.linuxandubuntu.com/home/h...word-in-ubuntu

[marlonmin]

One way is to log in with a "live" version then edit your user/password.

A simple web search turns up many help pages:

http://www.linuxandubuntu.com/home/h...word-in-ubuntu

The problem is how to get into the grub mode? The 'shift' key doesn't work for Kubuntu.

[jlittle]

The problem is how to get into the grub mode?

I presume you mean the grub menu. Also, I presume you mean your user password; Kubuntu normally does not have or use a root password (it inherits this behaviour from Ubuntu). On *buntus to get root we use sudo (or a GUI equivalent) and it asks for your user password.

The 'shift' key doesn't work for Kubuntu.

It's supposed to, I think, but I couldn't get it to work. (Maybe it's a timing thing, I tried hammering away to no avail.) Note that an askUbuntu post says it has to be the left shift key, maybe try that.

To get to the grub menu I had to edit /etc/default/grub to set GRUB_TIMEOUT to some positive number, and then run sudo update-grub. But that's a catch-22 for you.

(Edit, I've now tested the following, the bind mount stuff seems not to apply any more.)

If you can boot to a Live USB or CD, you can use a chroot to set the password. Get to a bash prompt from the USB, and work out where the Kubuntu linux root is. One way to do that is to run sudo blkid. For a UEFI system it might well be /dev/sda2. (With btrfs the subvolume is needed, usually "@", so one would add -o subvol=@ to the mount command.)

sudo mount /dev/sda2 /mnt
[s]for d in dev sys run proc; do sudo mount --bind /$d /mnt/$d; done # didn't work and it's not needed[/s]
sudo chroot /mnt

Now you can follow the instruction that apply after booting in recovery mode and remounting rw, namely

passwd [I]username[/I]

substituting your user name.

[SpecialEd]

The problem is how to get into the grub mode? The 'shift' key doesn't work for Kubuntu.

Did you see the part about booting a "live" version?

[claydoh]

Use the Esc key. Newer systems now use this instead of the shift key. You may have to try it a few times, some systems seem to have a very short window.

[marlonmin]

Yes, the 'ESC' key works. and Thank you all.

[jlittle]

Yes, the 'ESC' key works. and Thank you all.

That's great. It doesn't work for me, nor does left-shift. After about 5 attempts each, holding it down and a drum roll on the key. Ah well. I know well how to boot from USB, and change the grub time out value in the simplified grub.cfg I use.