Summary

We have reviewed the boot sequence in this chapter. As you have seen, it is not long, but it is complex and it is also very important as no system can run if it cannot boot. We have learned the main differences between a BIOS-enabled system and a UEFI one, which enables some capabilities but also has its own requirements. We have also learned about GRUB and its important role in the boot sequence, how to modify entries permanently with grubby, and how to make a one-time modification. We now know the main files to boot, such as the kernel, vmlinuz, and the initial RAM disk, initrd.

This chapter also showed us how to start in emergency and rescue modes, as well as how to intervene in a system to reset the root password.

We are now more prepared to handle any difficult situation in our systems with these tools and procedures. It's time to dive deeper and learn about kernel tuning and performance profiles in the next chapter.