How to Reset a Lost or Forgotten Password on Ubuntu Server

The Goal

To regain access to an Ubuntu server when the password has been lost, forgotten, or left behind by a departing sysadmin. This lab shows how to reset it using Ubuntu’s recovery mode—no installation media or ISO required.

The Lab

• Server: Ubuntu, physical or virtual
• Access: Console access—either direct or via hypervisor
• Mode: Recovery mode and root shell access

The Why

Passwords get lost. Admins move on. And sometimes a beautifully functioning home lab is rendered inaccessible by a simple case of forgetfulness. Ubuntu's recovery mode offers a built-in rescue path for just such moments—and all it takes is a few commands.

The How

1. Boot into Recovery Mode

• Reboot the server
• Hold Shift during boot to access the GRUB menu (on some systems, it’s Esc)
• Choose the kernel entry with (recovery mode)
• Press Enter to boot

2. Drop to Root Shell Prompt

• Once the recovery menu loads, select "root – Drop to root shell prompt"
• Press Enter

You’ll now be logged in as root—but in read-only mode.

3. Remount the File System

To enable write access:

mount -o remount,rw /

This remounts the root filesystem with read-write permissions so you can update passwords.

4. Reset the Password

For the root user:

passwd

For a specific user (e.g. rajinder):

passwd rajinder

You’ll be prompted to enter and confirm a new password.

5. Reboot the Server

reboot

After rebooting, use the new password to log in.

The Results

• Password successfully updated.
• You’ve regained access to the server.
• No ISO images, no reinstall, no downtime.

Whether it's a production box or your home lab, this method is quick, clean, and built right into Ubuntu.

The Conclusion

Recovery mode on Ubuntu is a lifesaver for forgotten passwords. When you've done it once, it's surprisingly straightforward. And while your manager may not throw a parade, you will have avoided a rebuild and kept the server operational.