Explain the Linux boot process from power on to login prompt

  • System goes through POST ( Reads BIOS settings and initializes hardware ).
  • System determines the primary boot device.
  • System reads Master Boot Record of device.
  • Depending on boot loader installed with either start Grub or LILO.
  • Boot Loader determines default kernel image.
  • Boot loader decompresses kernel image.
  • Kernel loads modules for all the hardware and initializes it.
  • Kernel starts the init process.
  • Init reads its configuration file ( /etc/inittab ) to determine the default runlevel.
  • Init starts processes located in the default runlevel’s rc directory.
  • Init starts processes in rc.local.
  • Init start TTY sessions and user is presented with a login prompt.