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CarpeNoctem
Asked: 2010-02-16 18:45:09 +0800 CST

Explain steps RedHat distros take to boot into Emergency mode?

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Please, I am not looking for a rehash of what's stated in RedHat's documentation regarding emergency mode. I would like to know what steps are involved from the time grub hands off to the kernel to the time you get a emergency mode login prompt.

I imagine /sbin/init is completely bypassed and therefore rc.sysinit bypassed as well. I don't however know what isn't bypassed or how emergency mode differs (intimately) with init=/bin/sh.

What sort of steps does the kernel take when given the emergency argument at boot time? Thanks!

linux startup kernel init

2 Answers

  1. Best Answer

    Normal situation:

    1. bios initialization
    2. bootloader
    3. kernel initialization
    4. init starts and enters your runlevel & execute:
      • /etc/rc.d/rc.sysinit
      • /etc/rc.d/rc and /etc/rc.d/rc?.d/
      • /etc/rc.d/rc.local
    5. X display manager

    In emergency mode you bypass 'rc.sysinit' and runs only 'sulogin' script by default. To see what is happening on your system see /etc/inittab.

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  2. No scripts are processed and you are given a root shell. Requires a password. Uses PAM if configured.

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