Symptoms
- Password rejected at login screen
- No password reset option offered
- Can't remember password after time away from the machine
- Locked out after a system change
Likely causes
- CommonSimply forgotten passwordThis is the most common reason and is fully recoverable with physical access.
- PossibleKeyboard layout mismatch causing wrong charactersA changed keyboard layout can make a correct password appear wrong.
- PossibleCaps Lock or Num Lock toggled unexpectedlyThis changes what characters are actually typed.
What to do
- First check Caps Lock and keyboard layout, and retry carefully in case of a simple mistyping issue.
- Reboot and access the GRUB boot menu (hold Shift or Esc during boot depending on setup).
- Select 'Advanced options' then boot into recovery mode.
- From the recovery menu, choose 'root' to get a root shell, or 'passwd' if listed.
- Run 'mount -o remount,rw /' if needed, then 'passwd [username]' to set a new password.
- Reboot normally and log in with the new password.
- If GRUB or recovery mode is unavailable, boot from a Linux live USB to reset the password via a chroot process instead.
Tools and parts
- Physical access to the machine
- Linux live USB (backup method)
When to call a pro
If full-disk encryption is enabled and you don't have the recovery key, a data recovery specialist may be needed, and full recovery may not be possible.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.