How Does Linux Boot Process Work? 

This is a good summary, but it seems like there's a lot going on behind the scenes in all of these process, especially systemD. Would be nice to cover that in a future video :)

There's a bit of a misconception about BIOS. MBR is limited to 2TB, but a BIOS doesn't need to be restricted to MBR, it could've moved to a different (likely proprietary) format... it's just that GPT and EFI were more flexible and the groundwork was already completed

Bravo si multumesc.E simplu,frumos pe intelesul tuturor...fara explicatii savante.CHIAR UN TUTORIAL...GENIAL DE SIMPLU!!!La mai multe inainte !!!

Good overview, but missing a discussion of ACPI, initramfs/initrd.

One of the best boot process summary's on RU-vid. Thanks for all the work and graphics.

Great content, always helpful and always impressive. Thank you very much for taking the time to make these.

Great summary and visualization of the entire boot process. Very well done mate!!!!

I was expecting that you would really be talking about the kernal boot process and not everything around. But in the end, I never saw an exhaustive explanation about the boot process in the first place so I am that to know that I did not miss out anything.

As has already been said, there is a lot going on in each of these steps. My major criticism is that step 5 simplifies away the usual mechanism of running some code from an initial ramdisk: this is done so that the kernel does not have to contain all the device drivers needed to load whatever modules it needs before the final root partition becomes readable. That also means that an earlier step needed to load the initial ram disk into memory and tell the kernel where to find it. Grub (or some other boot program like Lilo) will have done this already, so the Grub step should mention that it loads a filesystem containing drivers as well as libraries into ram before passing control to the kernel. And then, in my opinion, you need an extra step between 4 and 5 for the initial ram stage, that is used to get the system able to actually read the code it needs off the disks. While it does that the kernel only needs to know how to read the initial ramdisk. More detail follows... There are two exceptions to what i just said 1. If you compile your own kernel you can arrange that the kernel has all the drivers it needs built in (Gentoo users might do this, knowing in advance exactly what filesystem and hardware will hold the operating system) 2. Puppy (and most Live Disk systems) boot into the ramdisk and never leave it. For different reasons, both these exceptions slow down system loading (because either the kernel or the ramdisk is huge) but often speeds up running once the boot is complete because the kernel has what it needs in memory at all times, one way or another.

Great visualization of the entire boot process, Thank you.

That’s beautiful and enormous work! Great thanks.

Have never such a visually stunning explanation of a boot process. Amazing video Thankyou so so much for sharing. Piece of art with tons of knowledge

Very nicely explained and beautifully visualized presentation. I have to ask tho, would you like to make that same presentation again but for a Secured and TPM measured bootgraph ? If so, please do it, people and especially the linux community would need this in order to understand why the TPM makes booting so much more secure. I would even offer my help understanding a measured boot process (which I am pretty sure you would have no trouble understanding on your own).

I was looking for something like this. This is great thank you!

This is incredibly well explained and illustrated! Thank you so much!

Wow, I just loved it - I am recomending to my felow IT guys who ignore those initial steps. Regards from Brazil and keep posting!

Best Summary of the Boot process

KUDOS! I've never seen such nicer explanation for this.

Excellent presentation. Thank you for posting it.

This channel is absolutely brilliant. I am blown away! 0__0 wow

Very lovely & professional made

Nicely done! Good visual aids too

I was looking something like this and kind of explanation thanks man😊

Awsome, great job. thanks a lot for your time. excellent explanation!

Great overview. I think is good background info for any OS.

Sir, thank you for such creative tutorials please make one on Spark

I sept yesterday learning all this by myself and today, youtube recommended me this. If I had found this video, maybe I would have learned all that in 5 minutes.

One of the best channels in last few years

Thanks! Loud and clear

Thanks, it's a very good summary video with a good global presentation

This was excellent, well done.

thanks for the explanation! this helps!

I love your presentations! Which tool do you use to create or generate them with such a beautiful animation?

More detail please. A series would be good describing each and every nook and cranny.

thank your for this helpful explanation!

Great presentation! Thanks!

Nice explanation and great graphics.

Thank you sir. Nice diagrams too.

Great job! It looks clean, straightforward, and easy to understand. Could you tell me what software you used to create this video? I'm interested in making my own technical videos in the same manner.

Excellent presentation and narration; whats' used for your animations?

Great descriptions... 😊

very very nice. excellent animation. forcing us to view compulsorily immediately though we have plenty of pending works. it is like movie attracts us. go ahead.

Great video.. I could not have done this better like you Though I am a Linux user for the last 15 years.. Thank you

nice explanation best so far :)

this is awesome, the same core idea when develop embedded firmware as well

Nice video good explanation and presentation 👍

This is my favourite new channel.

wow amazing, which tool you use for graphical representation in your explanations? ill try for my students too. please tell me if you can

Nice and simple ! But you're missing the loading of initrd. I admit I can't remember from the top of my head when exactly it occurs. Would be a nice addition to your explanation.

The information density here is very high

Thank you for the information, as a follow-up will be great to take a step back and have instructions on how to identify if our system (desktop, laptop, mini PC, or server) supports UEFI for a faster boot, better functionality, and security. Thank you again!

Thank you, well done. :-)

It is possible to use gpt partitions without needing UEFI. Even old motherboards with intel 775 socket will boot using gpt partitions without UEFI: "Yes, it is possible to use GPT (GUID Partition Table) partitions without UEFI (Unified Extensible Firmware Interface). GPT is a partitioning scheme for formatting and partitioning hard drives, and it's independent of the firmware interface being used (UEFI or BIOS). However, the ability to boot from a GPT-partitioned disk depends on the firmware of your system. Most modern systems use UEFI firmware to boot, and UEFI is compatible with both GPT and the older MBR (Master Boot Record) partitioning scheme. If your system uses the older BIOS (Basic Input/Output System) firmware instead of UEFI, it may have limitations when it comes to booting from GPT disks. Some BIOS systems can boot from GPT disks using a compatibility support module (CSM), while others may not support GPT booting at all. So, in summary, while you can use GPT partitions without UEFI, the ability to boot from a GPT disk depends on the firmware capabilities of your system."

When Linux chooses to support initramfs boot, and selects the rootfs path to be packaged in the initramfs source file, it will try to boot in initramfs mode. In this way, the rootfs will be compressed and packaged in the same image file as the Linux kernel. Then uboot will load the whole image file into memory when the system is loaded. In this way, the rootfs cannot be modified in flash, and will be lost when the power is lost.

systemd-boot is great. No fuss just straight to the point !

What about the SPI flash? Coreboot/DepthCharge or uBoot and TowBoot? What about the details of gdm3 and starting the graphical shell?

I anticipate to implement a service daemon manager in my operating system soon! Currently it just handles the transferred ownership from my kernel and does nothing but outputting in tty mode

Missing initrd or initramfs part?

Excellent demo

awww I thought you're gonna go into more detail about primary and secondary boot loader

very nice video... loved it...

Спасибо, добрый человек.

Thanks for sharing

how do do you do these animations? its nice and clean!

Linux newbie here 🤓 Very nice video.

I bought your books 📚, but haven't had time to read, by I hope I will do soon.

Great !!! more please !!

Doesn't grub also load an initrd image as well as the kernel? Where does squashfs fit in?

Today I read chapter 5 on How Linux Works by press starch. You took about 30 pages and summarized them in 4:43 minutes, except the book of course went in more detail at each step. Plus it had all the different boot loaders listed, even ones that are dead and gone. Do you have a System D VS Wayland video yet?

High quality animation. Thank you for the effort. Can you make a video about Windows booting ?

I would have appreciated more time being given to the transition between the boot loader and systemd (the kernel initialization).

Great thanks

Well done!

Hey, can you do the same for Windows?

Where is initrd or initramfs? It is present in most if not all Linux system? Seems like you missed something.

2TiB drives was NOT a limitation of the BIOS firmware. If you had a very late version of a BIOS with the proper hardware, you could easily support sizes > 2TiB.

Although a thing to point out is that you don't need a boot loader now, you can just expose the kernel to UEFI and write flags directly into boot record.

Prior to boot loader what is the software that controls all these? Also how does a boot loader identify all the available kernals? like how does it know? is there already a software that reads this?

excellent!

Always impressive.

This seems more like a brief description of how *any* OS boots on a PC, just using the linux names for the later steps where it'll differ. Up to the boot loader step, there's not even an OS involved. And Windows uses a boot loader as well, it's just not called that and tends to be hidden from view for most people. Still, the same process. Code the hardwired system can find that loads the actual operating system. And whatever OS it is, the first step will usually be getting the kernel of the system going, drivers, etc. Same basic flow for any OS. Aside from the names used in those last steps, nothing here specific to linux. An actual OS specific discussion of the boot process would start with the kernel loading. It's from that point that OS's diverge. The boot loader itself can be setup to point to different kernels and/or different OSs itself, which is how a dual boot works.

I think this video could have extended itself to include the graphical boot process. The display manager which boots up the desktop environment.

thank you!

If initramfs also coved in this video then this could be the best one...

This question might not get answered but I’ll try anyway. What program do you use to generate those cool animations for your videos?

No way. I just guessed it right. I told exact same on my interview 😂.

thanks

How does this relate to hibernate and suspend? I.e. I assume some of the steps involved in boot would also have to happen after a wakeup from suspend/hibernate, but other things do not. What are the differences and similarities between a boot from scratch, and waking up from suspend/hibernate?

How to run two kernel at the same time. Can you ever switch processor type. Two clocks.

Very nice.

and loading the filesystem image?

Wonder why there is a stage 1 (initrd) and stage 2 in the Linux boot process

Nice, U can activate Dubbing to PT-BR ? Thanks !

GRUB2 can be replaced by SystemD-boot too...

Can you do s video like that but about templeOS?

Anyone.. Which software is used to make this video (animations)?

Have you got a full list how Linux boots because mine changes randomly over boots. The last boot event it decided to turn off my GUI, another time it decided to turn off the internet, another time is stopped using my drive sub-directories. How did Linux build that random booting sequence in and why?

Hey, thanks for the video lol

My linux mint struggles to start on its own despite having only one ssd and it's the main bootable device, it works well when I start it in safety mode but won't boot straight after I power my pc.

Graet video!