Linux is a free and open-source operating system that runs on computers, servers, smartphones, tablets, embedded systems, cloud computing platforms and more. The booting process of Linux is unique in its own way because it has many different types of boot options.
The linux booting process step by step is a detailed explanation of how the Linux booting process works.
You’ve probably noticed the time difference between pressing the power button on your computer and seeing the login screen on the display. Have you ever pondered what goes on in the background of the system at that time? During that time, your machine is booting, and the procedure is taking place in the background.
Let’s have a look at what occurs during the booting of Linux.
What is the procedure for booting?
The booting process refers to the whole process of your system starting when you click the power button, loading applications, and processing into main memory until you reach the login prompt.
The power button is turned on to supply electricity to the motherboard, allowing the computer to boot. Every operating system has its own booting procedure, regardless of which one you use or interact with.
Also see: What is Kali Undercover and how to set it up on Linux.
A Linux operating system’s booting procedure is divided into six phases.
The BIOS (Basic Input/Output System) is an acronym for Basic Input/Output System. At this point, BIOS conducts certain integrity checks before searching for the boot loader on your system’s hard drive, CD-ROM, or SSD.
The bootloader is a software that stores instructions for loading the operating system into memory. It loads the bootloader into memory when it finds the bootloader. The MBR Bootloader is controlled by the BIOS.
The first sector of a bootable disk (/dev/had or /dev/sda) contains the Master Boot Record (MBR). MBR is made up of three parts:
- Information about the primary boot loader (446 bytes) – It provides information on the operating system’s location specifics and how to load such information.
- Information about the partition table (64 bytes) – It keeps track of a disk’s partition information, such as where a partition begins and finishes.
- MBR Validity Timestamp (2 Bytes) – If the MBR becomes corrupted or incorrect, the validation timestamp is used to retire it.
These three combined make up an MBR with a size of 512 bytes or less. MBR and the GRUB bootloader load these information as soon as your system recognizes them.
Grand Unified Bootloader (GRUB) is a bootloader that includes information about several filesystems. When your system has several kernels installed, you’ll get a splash screen where you may choose the kernel you wish to work with.
It waits for you to choose your kernel image for a few seconds. If you don’t provide a kernel, it uses the default kernel and initrd image (Initial RAM Disk) from the grub.conf configuration file.
The kernel is the Linux operating system’s brain, and it manages all of the system’s processes. The kernel mounts the root file system, configures all of the hardware, and loads all of the required drivers at this point.
The kernel then unzips the initrd image, mounts it, and runs the /sbin/init command. Because the init program is always the first to execute, its process ID is always 1.
Also see: What is the Linux kernel?
In a Linux system, there are seven run levels. The system’s run level is decided at this point by looking at the initlevel file in the /etc/inittab file.
|1||Mode for a single user|
|2||Multiuser mode without the need of a network|
|3||Multi-user mode in its entirety|
|5||The GUI’s multiuser mode|
Run level 3 (Full multiuser mode) or run level 5 (Multiuser mode under GUI) are the default settings. When your system reaches the init stage, you should never utilize Run levels o or 6, since your system will shut down or reboot.
Many services begin to run as soon as your system boots up. Runlevel programs are these services and programs. There are various folders (/etc/rc.d/rc*.d/, where * may be any number from 0 to 6) for each run level, and the programs are loaded into your system based on the value of the run level that your system receives from the init stage.
These applications have names that begin with S (startup) or K (kill) and are used to turn on or turn off the computer.
These six steps take place in the background while your system is starting up. After you’ve completed all of these steps, you’ll be able to view the login screen.
Also see: How to Run Linux on Android Phones and Tablets.
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The boot process is the first part of the booting process. It is also known as the BIOS or firmware, and it starts by turning on your computer’s hardware. Reference: what is booting process.
Frequently Asked Questions
What is booting in Linux?
When a computer boots up, it starts from the beginning of the operating system.
What is the process of booting?
The process of booting is when your computer starts up. It can be initiated by pressing the power button, or by pressing the reset button on a laptop.
How does Linux boot process work?
The Linux boot process is the process that takes place when a computer boots up. It starts with the power-on self test (POST) which tests hardware and firmware components of the computer, followed by loading an operating system kernel from disk or RAM.
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