How to boot a Oracle linux 6/RHEL 6/CentOS6 server to Single user mode

 In this article we will cover How to boot a Oracle linux 6/RHEL 6/CentOS6 server to single user mode.

Run Levels

The run level determines the mode of operation of the server. The "/etc/inittab" contains an explanation of the run levels (0-6).

#   0 - halt (Do NOT set initdefault to this)
#   1 - Single user mode
#   2 - Multiuser, without NFS (The same as 3, if you do not have networking)
#   3 - Full multiuser mode
#   4 - unused
#   5 - X11
#   6 - reboot (Do NOT set initdefault to this)

Single User Mode

Single user mode is important because it gives you root access without needing the root password. This is very useful if you've forgotten,, the root password and need root access. 

Step 1:

Boot the server and press a key at the "Press any key to enter the menu" option.

Step 2: 

At the GRUB screen, press the "e" key to edit the boot parameters.

Use the arrow keys to move the highlight down to the "kernel ..." line and press the "e" key to edit it.

Add " 1" onto the end of the line, then press the return/enter key to return to the previous screen with the amended values.

Step 3: 

Press the "b" key to boot using the amended boot options. The server will now boot into single user mode.

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