The first step to reset the root password is boot the CentOS machine in emergency mode,
and for this process, we’ll use rd.break.
Start the system and, on the GRUB 2 boot screen,
=> press the ‘e’ key for edit:
Remove the rhgb and quiet parameters from the end, or near the end, of the linux16 line, or linuxefi on UEFI systems.
=> linux16 bah bah bah...
Add the following parameters at the end of the linux16 line on x86-64 BIOS-based systems,
or the linuxefi line on UEFI systems: rd.break enforcing=0
add this end of line=> rd.break enforcing=0
When you finish, press ctrl + x to load the system. Finally you’ll boot in emergency mode.
#mount -o remount,rw /sysroot
#chroot /sysroot
#passwd
If the system is not writable, the passwd tool fails with the following error:
Authentication token manipulation error
#touch /.autorelabel
#mount -o remount,ro /
and type exit 2times
#exit
#exit
If you omitted to relabel files enter the following command to restore the /etc/shadow file's SELinux security context:
#restorecon /etc/shadow
Enter the following commands to turn SELinux policy enforcement back on and verify that it is on:
#setenforce 1
#getenforce
show "Enforcing"
Done
