I am using Ubuntu 11.04 on a Dell 1510 laptop. Something happened and I was not able to install software using sudo or access my other partitions (that required a root password). Hence, I went into the recovery mode and edited the /etc/sudoers file adding the following :Thereafter, sudo started working but I am still unable to access my partitions that require me to enter the root password. Also, I am unable to install any software through Ubuntu S/W Centre as it also requires the root password.

There is an Oracle account also that got created after I installed Oracle 10g, but I always use my own account that was created during installation to log in
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Try booting into single user. This will bring you to a root prompt. Run 'passwd root' to reset the root password. (Recovery mode *may* do the same thing but I don't remember.)

Here are specific instructions for the method I am suggesting:

http://www.debuntu.org/recover-root-...-mode-and-grub