After a long time i am here with an security trick. Many occasion we need to move into single user mode , which is very simple. But this can be security risk also to overcome this either we can use password in grub boot loader or we can go with following simple solution
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open /etc/inittab file and put following line in this
~~:S:wait:/sbin/sulogin
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open /etc/inittab file and put following line in this
~~:S:wait:/sbin/sulogin