reset redhat 5 password +boot
When you lost your root password in a RedHat Linux Based systems you should first have access to the console, (the machine itself).
Power on, or reboot as needed.
and as soon as you get the GRUB GUI screen (if you do not you may need to press CTRL-X )
1.Now you should press ‘e’ and you will get this screen.
2.Select the image you would like to boot, and press ‘e’ again, and as soon as you get the nex screen
3.Insert an space and the number one ‘1’ as shown in the image.
4.After that press ENTER and ‘b’ and ENTER again.
Finaly you should see the bash prompt booted as a single user and you will have no need to enter a password.
Now you can change the password like this
If you need to change other users password do # cat /etc/passwd (check users) then # passswd
And you will have againg your system working.