Ubuntu users

[lapfog_1]

1. boot to single user and then use passwd to modify password for any account

To boot into single user mode you edit the boot instructions for the GRUB menu entry you wish to boot and add the kernel parameter/option single. Brief instructions for how to do this are below.

Hold down the left Shift key while rebooting to bring up GRUB menu
Select (highlight) the GRUB boot menu entry you wish to use.
Press e to edit the GRUB boot commands for the selected boot menu entry.
Look near the bottom of the list of commands for lines similar to

linux /boot/vmlinuz-3.2.0-24-generic root=UUID=bc6f8146-1523-46a6-8b
6a-64b819ccf2b7 ro quiet splash
initrd /boot/initrd.img-3.2.0-24-generic
Change the middle line in (4) by adding the kernel boot parameter single to the end of the line (i.e. after ro quiet splash).

For this example you would change:

6a-64b819ccf2b7 ro quiet splash
to

6a-64b819ccf2b7 ro quiet splash single
Press either Ctrl+X or F10 to boot using these kernel options.

Note: These changes are not persistent. Any change to the kernel boot options made this way will only affect the next boot and only if you start that boot by pressing either Ctrl+X or F10 while still in GRUB edit mode.