add myself back to sudo'ers list

Question

i've got a computer running Ubuntu 9.10 Server, and i added myself to a new group using the following command:

sudo usermod -G my_group me

i learned that command removes me from all the groups i was in (like the sudo group), and adds me to only my_group.

the problem:

• i was the only one in the sudo group, there is now no one
• i never enabled/created a root
• i don't remember setting one up when i installed the OS
• when i type su and try the same password as my account (the account i set up when i installed the OS), it is not accepted

did i screw up my computer? do i need to spend an hour re-doing everything? or is there a way to recover?

Answer 1

There is a root account already installed, since you don't know the password you can access is from single user mode then change your accounts groups.

to boot into single user mode:

• At the GRUB menu, use the arrows to select the boot entry you want to modify.
• press e to edit the entry
• use the arrows to go to kernel line
• press e to edit this entry
• at the end of the line add the word single
• press ESC to go back to the parent menu
• press b to boot this kernel

You will be presented with a shell prompt and you'll be logged in as root without providing a password, you can test this by running whoami. You may also need to mount certain partitions depending on your setup and where the binaries you'll need are located.

Answer 2

try passwd root it might work if you never set up root

Answer 3

here's what i got to work:

• reboot the computer by holding ctrl+alt+del at the initial log in screen after boot (physically at the machine, not ssh)
• hold the esc key while booting
• the computer entered some weird state where it has both a root shell and a login prompt. i was able to enter a command in between the pauses while the login prompt was checking my username/password
• i added my username to the sudo line in /etc/group

i don't know what i was in, but i don't think it was the grub bootloader. any information on why it just gave me a root shell when i held esc during boot instead of grub would be appreciated, thanks.