The Linux Boot Process

The first step in understanding the many daemons used for VoIP is to understand the Linux boot process. This page walks you through the boot process.

  1. The computer turns on and boots to the Basic Input Output System (BIOS) which performs a Power On Self Test (POST). This checks the hardware and specifically for a video card, RAM, keyboard, floppy drives, hard-drives, CD ROM drives and checks for any cards in the PCI slots.
  2. Next the BIOS launches the first stage boot loader on the MBR of the primary hard disk and loads itself into memory
  3. The second stage boot loader (grub) boots from the /boot/grub partition. Grub allows you to boot to different versions of the kernel and even to different operating systems.
  4. The second stage boot loader (grub) loads the kernel into memory, which in loads the kernel modules and mounts the root partition read-only.
  5. Then the kernel reads the /sbin/init program which loads all services and user-space tools then mounts all the partitions listed in /etc/fstab.
  6. Finally depending on which running mode mode the init program is set to , the user is presented with a command line or an X Windows login screen for the freshly booted Linux system.

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Copyright July 2013 Eugene Blanchard