RHEL 7 / CentOS 7 : Single User Mode / Recovering / Reset Root Password

Hello,

Setting up the root password is a mandatory part of the Red Hat Enterprise Linux 7 / CentOS 7installation.

If you forget or lose your password, it is possible to reset it. Now it is known as Rescue Mode / Emergency mode in CentOS / RHEL 7, Previously in RHEL / CentOS 5/6 It was “Single User Mode”.

Note: In GRUB 2, resetting the password is no longer performed in single-user mode as it was in GRUB included in Red Hat Enterprise Linux 6. The root password is now required to operate in single-user mode as well as in emergency mode.

systemd_recover_root_password

Process: Resetting the Root Password

1. Please follow this procedure carefully, any mistake can make your system / Linux unstable, Perform this own your on risk.
   q
2. Start the system and, on the GRUB 2 boot screen, press the e key for edit.
3. Add the following parameter at the end of the linux line, or linuxefi on UEFI systems (In case of  VMWare like KVM or VirtualBox use rb.break instead of init=/bin/sh):

init=/bin/sh

The Linux kernel will run the /bin/sh shell rather than the system init daemon. Therefore, some functions may be limited or missing.

Important

The rhgb and quiet parameters must be disables in order to enable system messages.

4. Press Ctrl+x to boot the system with the parameter.

The shell prompt appears.

5. The file system is mounted read-only. You will not be allowed to change the password if the file system is not writable.

To remount the file system as writable, run the mount -o remount, rw / command.

6. Run the passwd command and follow the instructions displayed on the command line to change the root password.

Note that if the system is not writable, the passwd tool fails with the following error:

Authentication token manipulation error

7. To make sure that SELinux context of the files that were modified is restored properly after boot, run

touch /.autorelabel

8. Run the exec /sbin/init command to resume the initialization and finish the system boot.

Running the exec command with another command specified replaces the shell and creates a new process; init in this case.

Alternatively, if you wish to reboot the system, run the exec /sbin/reboot command instead.