Interrupt The Boot Process In Order To Gain Access To A System

General Information

If you cannot perform this procedure, you will fail the entire exam.

Recover the root user's password

1. Interrupt boot process at grub menu (move an arrow key up or down to stop the grub boot countdown)
2. Press “e” to edit the grub menu entry
3. Navigate to the line starting with “linux16”; this is the kernel
4. Append to the end of the kernel entry (Ctrl+e to go to the end of the line)

   rd.break enforcing=0

   1. rd.break ⇒ stops early in the boot process (when initramfs is in memory and has not mounted the root file system as rw yet)
   2. enforcing=0 ⇒ set SELinux to permissive mode
5. Ctrl+x to continue boot process, it will stop within the initramfs shell
6. Remount the sysroot file system as read/write

   mount -o remount,rw /sysroot

7. Change root to that root file system

   chroot /sysroot

8. Change root password

   passwd

9. Exit the chroot jail and initramfs shell

   sh-4.2# exit
   switch_root:/# exit

10. The system will continue to boot
11. Login as root with the new password
12. Restore SELinux file context to /etc/shadow

    restorecon -v /etc/shadow

13. Set SELinux to enforcing again

    setenforce 1