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

Read more: RHEL 7 / CentOS 7 : Single User Mode / Recovering / Reset Root Password @ All Linux User's Blog http://www.tejasbarot.com/2014/08/06/rhel-7-centos-7-recovering-root-password/#ixzz3aO9hLnsB
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RHEL 7 / CentOS 7 : Single User Mode / Recovering / Reset Root Password

Posted in August 6, 2014 ¬ 5:42  pmh.-Post metadata unknown- 6 Comments »

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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.