I was using Ubuntu 11.10 for a long time and once i lost my password. I have gone through various searches and here i am present with the solution of it through which you can reset your password manually.
you can set it with two methods the first is by booting it in recovery mode and the second is by using any live OS.
I will talk about the first method..
first step is to boot up Ubuntu, press and hold “shift” key while the machine is booting..you will get the GRUB menu.
select the second option which is recovery mode and press enter. After pressing enter the system will start booting and you will get a list of options. We will have to make file system writable so that we can change our password. To make it writable select the 3rd option which is remount and press enter. You will get a picture once press enter you will get recovery menu with a list of options.
Select the last option root and press enter. if the root account password is not set then you will get a shell prompt and you can enter the command to reset the password of any account #passwd enter the new password and confirm it by entering again. Now enter command ‘sync’ and press enter.After that a prompt will come with written password updated successfully.Now enter the command ‘reboot-f’ to reboot.
You have successfully reset your password now you can enjoy working with your Ubuntu OS once again.