Reboot your Server, at the bootloader screen select the kernel you would like to boot it with (usually the latest one) and hit ‘e’

In the next screen, find the line that refers to the kernel

• For RHEL/CentOS 7, the line starts with ‘linux16’.
• For RHEL/Centos 8x, and Fedora the line starts with ‘linux’.

Add ‘rd.break‘ at the end of kernel line and press Ctrl-x

Now the server will boot into OS rescue mode

switch_root:/#.

Now, remount root partition in read/write mode

#mount -o remount rw /sysroot

Next, switch to root directory

#chroot /sysroot

At this point you can change the root password

#passwd <enter>
*<new password>*
*<repeat new password>*

Next step is for SELinux to allow new file changes – such as password reset in our case.

#touch /.autorelabel

This step will take some time to relabel, as it depends on filesystem size

Once complete, Exit Server

#exit

then, Restart server

#reboot

Validate new password has been set on Server after reboot by logging in with root account.