In this video, I want to explain the different phases that are happening when you are booting
Linux. It all starts on the top with the firmware. The firmware is your hardware. And from your
hardware, you get to either the UEFI or BIOS. And then the part that is interesting for
Linux is going to start. And that will be where on disk, the GRUB2 bootloader is loaded.
The GRUB2 bootloader is loading the kernel. And the kernel is coming together with the
init RAMFS, the initial RAM file system. Then kernel is loading PID1. And PID1 is going
to add systemd. And systemd is the manager of everything. And in systemd, there are two
phases that can be distinguished. There is the phase of what I will call early boot.
Early boot is about all the essentials in the systemd environment. Next, there is also
the part where the services are loaded. And once the services are loaded, you are going
to load your shell. And the shell is where the user is going to log in.