Linux Password Reset


Resetting a Root Password in Ubuntu

In some situations, you may need to access an account for which you’ve lost or forgotten a password.

Step 1: Boot to Recovery Mode

Restart your system. Once you see the splash screen for the computer manufacturer, hold down the shift key. The system should come up with a black and white GRUB, or boot menu, with different Linux kernel versions displayed.

Select the second one from the top – the highest revision, followed by (recovery mode). Press Enter.

Step 2: Drop Out to Root Shell

The system should display a menu with different boot options. Use the arrow keys to navigate to the option labeled root and press Enter.

The system should respond by giving you a command-line interface with a prompt.

Step 3: Remount the File System with Write-Permissions

Right now, your system only has read-only access to your system. That means it can look at the data, but cannot make any changes. But we need write-access to change the password, so we’ll need to remount the drive with the appropriate permissions.

At the prompt, type:

mount –o rw,remount /

Press Enter. This should allow you to make changes to the data on the hard drive.

Step 4: Change the Password

At the prompt, type:

passwd username

Substitute the name of the user for username, then press Enter. The system asks you to type a new UNIX password and then to retype it.

Once you’ve entered and confirmed the new password, reboot the system by entering the following:

shutdown –r

Hit Enter, and your system should restart. Don’t press any keys, let the system come up to the login screen, and test to make sure the new password works.

Changing the Root Password in CentOS

Changing a password in CentOS is almost identical to changing it in Ubuntu.

Step 1: Access the Command Line (Terminal)

Right-click the desktop, then left-click Open in Terminal.  Or, click Menu > Applications > Utilities > Terminal.

Step 2: Change the Password

At the prompt, type the following, then press Enter:

sudo passwd root

The system should prompt you to enter your existing password. Do so, then follow the prompts to enter and confirm a new root password.

change root password in centos

Reset Root Password in CentOS

This is a similar process as in Ubuntu, with a couple of variations.

Step 1: Access Boot Menu

Restart the system, then tap the Esc key about once per second to launch the GRUB menu.

Step 2: Edit Boot Options

Use the arrows to highlight the version of Linux you boot into, then press e.

Use the arrows to highlight the line that starts with kernel or Linux.

Press E.

At the end of the line, add a space then type single. Press Enter, then boot into single-user mode by pressing Ctrl-X or B. (The system will display the command to use.)

Step 3: Remount the Drive

You should have a command line, and you’ll have root privileges. To enable read/write access on your hard drive, type the following:

mount / -o remount,rw
Step 4: Changing the Password

Type the following:

passwd

Press Enter, and the system should prompt you to enter and confirm a new password.

Step 5: Restart

Type the following, pressing enter after each line:

mount / -o remount,ro
sync
reboot

Your system should restart. Confirm that your new password works by logging in.

https://phoenixnap.com/kb/how-to-change-root-password-linux


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