How does Linux kernel boot?
In UEFI systems, the Linux kernel can be executed directly by UEFI firmware via EFISTUB, but usually uses GRUB 2 or systemd-boot as a boot loader. The stage1 is loaded and executed either by the BIOS from the Master boot record (MBR).
What is Linux kernel What is it for and how is it used in a boot sequence?
Overview. The Linux® kernel is the main component of a Linux operating system (OS) and is the core interface between a computer’s hardware and its processes. It communicates between the 2, managing resources as efficiently as possible.
What is the order of the Linux boot process?
The boot sequence starts when the computer is turned on, and is completed when the kernel is initialized and systemd is launched. The startup process then takes over and finishes the task of getting the Linux computer into an operational state. Overall, the Linux boot and startup process is fairly simple to understand.
What is kernel initialization in Linux?
The kernel initializes hardware as well as kernel data structures. The kernel command line is saved. Hard-drive information is retrieved from the BIOS. The memory size is determined, again through the BIOS. The hardware is prepared to move to protected mode.
How many levels are there in Linux boot process?
6
An operating system (OS) is the low-level software that manages resources, controls peripherals, and provides basic services to other software. In Linux, there are 6 distinct stages in the typical booting process.
How large is the Linux kernel?
A standard compiled and compressed kernel is around 2 MB, modules like 10 MB.
What are the four steps of the Linux boot process?
The booting process takes the following 4 steps that we will discuss in greater detail: BIOS Integrity check (POST)…
- The BIOS Integrity Check (POST)
- The Bootloader (GRUB2)
- Kernel Initialization.
Is init part of kernel?
Init is the parent of all processes, executed by the kernel during the booting of a system. Its principle role is to create processes from a script stored in the file /etc/inittab. It usually has entries which cause init to spawn gettys on each line that users can log in.
Where is Linux kernel entry point?
The start_kernel is the entry of the generic and architecture independent kernel code, although we will return to the arch/ folder many times. If you look inside of the start_kernel function, you will see that this function is very big.
Which is the process number 1 on Linux startup?
Since init was the 1st program to be executed by Linux Kernel, it has the process id (PID) of 1. Do a ‘ps -ef | grep init’ and check the pid. initrd stands for Initial RAM Disk. initrd is used by kernel as temporary root file system until kernel is booted and the real root file system is mounted.
Can you boot without a bootloader?
Since version 3.3. x, and ONLY on EFI machines, it is possible to boot the Linux kernel without using a bootloader such as iELILO or GRUB. You will experience shorter boot times by using this, but a less interactive boot in case you need to make some diagnostics.