Understanding the Linux startup process
Boot Camp
If you want to troubleshoot startup issues, you need a clear understanding of how Linux boots.
This article explains the process through which the Linux kernel loads. In a more technical sense, it explains how the kernel gets into memory and what it actually does until the first user process begins its execution.
Boot Processes
At a very high level, the Linux boot processes pass through the five steps described below. Some texts can describe it in four or six steps; however, the basic mechanism remains the same. The boot process starts at the moment either when you start a shutdown system or restart an already running system.
Irrespective of the computer or OS standard ("IBM-compatible"), computer systems use either the classic BIOS/MBR [1] boot process or the modern UEFI/GPT boot process. UEFI firmware and conventional BIOS both manage system boot, but the boot method and settings differ for each.
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