How To Reset Root User Password In Arch Linux, CentOS And Ubuntu

A while ago, we described how to reset root user password in Unix (FreeBSD). Today, we will see how to reset or recover root user password in Linux. Trust me, resetting root user password on Linux is very easy. Even an intermediate Linux user can easily reset the root user password by following the methods described below. Please note that you can reset the password only if you have physical access to the system. For remote systems and VPS, you might need your service provider's help.

I tested this guide on the following three distributions:

• Arch Linux,
• CentOS,
• Ubuntu.

However the steps are almost same for other distributions as well.

First, we will start from Arch Linux.

1. Reset root user password in Arch Linux

This method was tested in Arch Linux, however It may work on other Arch based Linux distros such as Antergos, Manjaro Linux etc..

At the GRUB boot menu, select the Arch Linux entry by using the arrow keys.

Arch Linux GRUB boot menu

Press e to edit the boot menu entry. Find the line that starts with word linux:

linux          /boot/vmlinuz-linux  root-UUID=d474f2-e6a2-4cc3-9899-aa98af13  rw  quiet

At the end of the above line, add the following line:

init=/bin/bash

Refer the following screenshot.

Edit GRUB boot menu in Arch Linux

After appending the above line, press CTRL-X or F10 to continue booting into the single user mode. This change will be only temporary and will not be saved in your boot menu.ist file.

Now, you reached the single user mode.

Type the following command to mount your root (/) file system in read/write mode.

mount -n -o remount,rw /

Then, change your root user password using command:

passwd

Enter the new password twice.

Reset root user password in Arch Linux

Finally, type the following command to apply the changes and start your Arch Linux in to normal mode.

exec /sbin/init

Voila! You can now log in to your Arch Linux server using the new root user password.

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2. Reset root user password in CentOS 8.x

To recover or reset Root user password in CentOS 8 and RHEL server editions, refer the following guide.

• How To Reset Root User Password In CentOS 8 / RHEL 8

3. Reset root user password in CentOS 7.x

We can do it in two methods. Both are slightly different, but easy. This method will also work on RHEL 7.x, Scientific Linux 7.x.

Method 1:

Power on your CentOS 7 server. At the boot menu, select the Kernel you want to boot up and press e to edit the selected boot entry.

CentOS Grub Boot Menu

Find the line rhgb quiet :

Edit CentOS Grub Boot Menu Entries

...and replace it with init=/bin/bash

Modify kernel parameters

Then press CTRL+X to enter into single user mode.

Type the following command to mount root (/) file system in to read/write mode.

mount -o remount,rw /

Mount root file system in to read, write mode in CentOS

Now, change the root user password with command:

passwd root

Enter the new password twice.

Reset root user password in CentOS 7

Finally, run the following command to update SELinux:

touch /.autorelabel

Then, type the following command to apply changes and restart CentOS 7:

exec /sbin/init

Enable SELinux relabeling on reboot

Now, you'll be able to log in to CentOS 7 as root user with new password.

Method 2:

At the GRUB boot menu, select the boot entry and press e to edit the selected item.

CentOS Grub menu

Find the line ro :

Find ro krnel parameter entry

Change the ro line to rw and add an extra line init=/sysroot/bin/sh

Modify kernel parameters

Press CTRL+X to enter in to single user mode.

Then type:

chroot /sysroot/

Mount root file system in read, write mode

Then change the root user password with command:

passwd root

Reset root password in centos

Update SELinux with command:

touch /.autorelabel

Reboot your system.

exit

reboot

Now, you can log in to the system with new password.

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4. Reset root user password in CentOS 6.x

If you want to reset root user password for CentOS 6.x systems and older versions, then follow these steps. This method will also work on RHEL 6.x, Scientific Linux 6.x.

At the boot menu, select the Kernel you want to boot up and press e to edit the selected item.

CentOS 6 grub boot menu

Select second line (Starts with the word Kernel) and press e to edit that line.

Edit centos 6 grub boot menu

Go to the end of the line and type S to start in to the single user mode.

Go to single user mode in centos 6

Then, press ENTER key and press b key to boot into to single user mode.

Mount the root (/) file system in read/write mode:

mount -o remount,rw /

Change the root password with command:

passwd root

Finally restart your CentOS 6 server.

sync

reboot

Reset root user password in CentOS 6

You can now able to login with new password.

5. Reset sudo user password in Ubuntu

I tested this how-to on Ubuntu 15.10 server, however it might work on other Ubuntu versions like Ubuntu 15.04/14.10/14.04 etc.

You can do it in two methods.

Method 1:

At the Grub boot loader menu, select the Kernel you use and press e to edit the entry.

Find the line that starts with word linux. Add the following line at the end.

init=/bin/bash

Edit Ubuntu grub boot menu

Then, press CTRL-X or F10 to boot in to single user mode.

Type the following command to mount root (/) file system in to read/write mode.

mount -o remount,rw /

Then, change the password of your administrative account using command:

passwd sk

Here sk is my administrative account.

Type the new password twice.

Reset sudo user password in Ubuntu

Finally, type the following command to start Ubuntu with updated password.

exec /sbin/init

Now, you'll be able to log in with new password.

This method is so easy. Still curious to know another way to reset the password? read on.

Method 2:

At the GRUB boot leader menu, select Advanced options for Ubuntu entry.

Choose advanced options in grub menu

Select the second option i.e recovery mode.

Select recovery mode

You'll see the list of recovery options. Select root Drop to root shell prompt option.

Go to root shell prompt in ubuntu

Now, you'll be reached to the single user mode.

Type the following command to mount root (/) file system in read/write mode.

mount -o remount,rw /

Then change the password of the administrative user, for example sk, using command:

passwd sk

Enter the new password twice.

Reset sudo or administrative user password in Ubuntu

Then, type exit to return back to the recovery menu. Select Resume to start your Ubuntu system.

Resume normal boot

You might see the following message that says: You are now going to exit the recovery mode. Press ENTER to continue.

Exit recovery mode

That's it. You can now able to login with new password.

All of the above methods should work on both Desktop and server editions.

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What if I don't know the user name?

I don't want to reset the root user password, but the other normal user's password. How can I do it? Or You might ask I am going to reset the password of my client system, and we both don't know the username. Is it possible to reset the password of a specific user? Yes, you can.

After entering into the single user mode, you can view the list of existing users with command:

$ cat /etc/passwd

Sample output:

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
systemd-timesync:x:100:103:systemd Time Synchronization,,,:/run/systemd:/bin/false
systemd-network:x:101:104:systemd Network Management,,,:/run/systemd/netif:/bin/false
systemd-resolve:x:102:105:systemd Resolver,,,:/run/systemd/resolve:/bin/false
systemd-bus-proxy:x:103:106:systemd Bus Proxy,,,:/run/systemd:/bin/false
syslog:x:104:109::/home/syslog:/bin/false
messagebus:x:105:110::/var/run/dbus:/bin/false
uuidd:x:106:111::/run/uuidd:/bin/false
sshd:x:107:65534::/var/run/sshd:/usr/sbin/nologin
sk:x:1000:1000:sk,,,:/home/sk:/bin/bash

Or, you can only list the usernames with command:

awk -F':' '{ print $1}' /etc/passwd

Sample output:

root
daemon
bin
sys
sync
games
man
lp
mail
news
uucp
proxy
www-data
backup
list
irc
gnats
nobody
systemd-timesync
systemd-network
systemd-resolve
systemd-bus-proxy
syslog
messagebus
uuidd
sshd
sk

The above commands are same for many Linux distributions.

Conclusion

In this tutorial, we have learned how to reset the root user password, and also the normal user's password. Do not blindly trust that you're safe after setting up a strong password for your root user account and other system accounts. As you can see in this tutorial, the passwords can be easily reset within few minutes, no matter if it's either root or normal user. We must be more careful and encrypt our data, partition and of course we should setup a strong password for GRUB boot loader in order to protect our system. Refer the following guide to know how to setup a password to the Grub boot loader.

• How To Password Protect GRUB Bootloader In Linux