To reset a user or root password, turn on the desktop or server and begin pressing the Esc key or Shift on your keyboard as soon as turn push the power button… to display Ubuntu boot menu. If your timing is wrong and you miss the boot menu, you’ll have to restart the machine and try again until you see the screenshot below…
On the menu, select *Advanced options for Ubuntu
Next, select *Ubuntu, with Linux.x.x-generic (recovery mode) .. select the recovery mode for the same Grub version as the default… they both should have the same version number…
Next, use the scroll key and scroll down on the list and select root as shown on the screen below, then press the Enter key
Next, run the commands below to mount the shell with read / write permissions
mount -rw -o remount /
After running the above commands, the shell should be remounted with read/write permissions. Now you can run limited sets of commends, including password change commands for user and root.
To reset a user password, run the commands below, replacing username with the real account name or the user.
sudo passwd username
When you run the above commands, you’ll be prompted to create and confirm a password for the account name you mentioned. create it and you’re done.
Next, type reboot to restart the desktop or server and begin using the new password you just created.
This is how one resets a user or root password on Ubuntu servers and desktop.
