Restarting the Linux system in a single user mode for diagnostics

About this task

This task must be done on the head of the server since it is executed prior to network services being available.

	Note:
	Restarting the Linux system in a single user mode requires a password.

Reboot the system or power on the system.
As soon as BIOS ends, start typing ESC. The screen is blank at this time and the window is only a few seconds long.
If the grub screen shows up, proceed with the next step. Otherwise wait till the system boots and then reboot again.
Type p to enter the boot loader password.
Type in the boot loader password that you have set in first root login.
Type a to append the line.
Scroll down to the linux... line.

This line tells GRUB 2 which kernel to boot.
Go to the end of the line, enter a space by pressing the space bar and then type single .
Press Enter to exit edit mode.

The system will then boot into single user mode.
Type the root password when the system prompts.
Type the command runlevel. It should respond NS, where the S stands for single user.
Perform diagnostics.
Press Ctrl-D to return to normal operation.