Linux on Boot (bootstrap)

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Computer booting is a mysterious process. We just press the power button to see the progress bar on the screen or a line of output, until we reach the login interface. However, computer booting is an exceptionally fragile process, and our full expectation of the login interface may not appear, but a command line or error message. Understanding the computer boot process helps us to fix possible problems with booting up.

The initial stage

When we turn on the computer, the computer automatically reads the stored program from the BIOS of the motherboard (Basic input/output System). This procedure usually knows some hardware directly connected to the motherboard (hard disk, network interface, keyboard, serial port, and port). Most of the BIOS now allows you to start your computer by selecting one from a floppy disk, CD-ROM, or hard disk.

Next, the computer will read the starting bytes from the storage device of your choice (for example, CD-ROM is bytes, if we start from the CD-ROM). This bytes is called the Master Boot record MBR (Master boot recording). The MBR tells the computer to load the boot loader (boot loader) from one of the devices ' partitions (partition). Boot Loader stores information about the operating system (OS), such as the name of the operating system, the location of the operating system kernel (kernel), and so on. The usual boot loader are grub and Lilo.

The boot loader will then help us load the kernel. Kernel is actually a program to operate the computer, it is the kernel of the computer operating system, the main task is to manage the computer's hardware resources, as a software and hardware interface. Any operation on the operating system is communicated to the hardware via kernel. Windows and Linux each have their own kernel. The narrow-sense operating system refers to the kernel, generalized operating system including kernel and kernel above the various applications.

(Linus Torvalds is not so much the father of Linux as thefather of Linux kernel.) He is still responsible for the development and maintenance of Linux kernel. As for Ubuntu, Red Hat, which is based on the same kernel, includes a more complete version of the operating system for different applications and interfaces. )

In fact, we can install boot loader on multiple partitions, each boot loader corresponds to a different operating system, and select the boot loader we want to boot when we read the MBR. This is the principle of multiple operating systems.

Summary: BIOS, MBR, boot loader, kernel

Kernel

If we load a Linux kernel,linux kernel start working. Kernel first reserves the memory space it needs to run, and then detects the computer hardware through the driver (driver). This allows the operating system to know what hardware is available. The kernel will then start an init process. It is a 1th process in a Linux system (Linux does not have a process number No. 0). In this, kernel completed the computer start-up phase of the work, the handover to Init to manage.

Summary: Init process kernel

Linux on Boot (bootstrap)