Hi,
Could you Help me for the following issue happened.

plenty of docs out there... https://www.google.co.uk/search?q=re...password+reset

but in brief, at the grub screen hit e, add a "1" to the kernel options line. Hit esc and then b to boot. when logged in run "passwd" and give a new password

Answer = boot into single user mode.

When you reboot your machine and you see the Red Hat splash screen, hit the esc key. Then select the kernel option at the grub menu and hit "e" for edit. Then hit the space bar once, and then type "single" or "1" and then the enter key. Hit "b" to boot into that option you just edited and the machine will boot into the root user and all you have to do is type "passwd" and you'll be changing the root password. Hopefully your system is not setup to password protect single user mode. Goodluck.

helpful!!!!