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.
- 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.
- Next the BIOS launches the first stage boot loader on the MBR of the primary hard disk and loads itself into memory
- 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.
- The second stage boot loader (grub) loads the kernel into memory, which in loads the kernel modules and mounts the root partition read-only.
- 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.
- 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.