Linux Startup process

Here's a quick no nonsense guide to how linux boots up.

  • When a linux system is started, Linux Loader (GRUB or LILO usually) loads the kernel.
  • Initially, when LILO or GRUB calls kernel, the kernel is uncompressed and kernel starts checking hardware attached, loads the required modules.
  • When all hardware modules or drivers are appropriately loaded, Kernel opens root volume (/) in read only mode.
  • Kernel checks if root volume has any problems. If no problems are detected, the root volume is mounted as read-write.
  • Once the above step is done, kernel executes a process called init.
  • When init is done, the linux is up and running.
  • init is highly configurable with various customizations.