04.1 (Conspect) SystemBoot

Pre-system loading consists of 4 parts (actually 5).

1. What the computer does without looking at any external devices at all.
2. Loading from the device we selected, a small loader (primary loader).
3. A large loader (secondary boot loader). The secondary loader loads the kernel, and in the case of Linux, also the starting virtual disk, because it is easier to do this from Linux itself than from some external program.
4. Init is the father of all processes, whose task is to start all the other processes that make up the operating system. The entire system will stop if the Init stops.

Starter kits

Starter kits- automatic kits that are practically not checked for usability. They are checked for performance and what packages they consist of, but they are not full-fledged distributions. Any script wraps around the corresponding service and supports several standard parameters:

1. Start
2. Stop
3. Restart
4. Status.

Different services start and end in completely different ways. Since we want to start them all in turn, they are cut off by the shell script "start-stop", and instead of specifying special parameters for starting the service, they are the same. The order of loading services is lexicographic. The idea is that all links are correctly named. Systemd- the system that should solve all the tasks of starting the operating system. Systemd solves problems such as startup time and large expenses for executing shell scripts, as well as some things related to the insufficiency of the shell script alone to run the operating system. We have a loading graph, that is, something starts first, then a few more pieces are started to choose from in any order, then something else, some of them must be started before others are started. There is a dependency on what runs before what. This dependency is described by unit. The service section describes how to launch it. Systemd still suffers from the fact that it was developed not as an Operating System management system, but as a system to speed up its loading. It has a lot of tools for checking who was loaded the longest, etc. But there is no tool for optimizing and working with the graph.