How Linux Kernel Prints Text on Screen 

- The display mechanism the kernel chooses depends on the setup, this is what it chose in the case of standard QEMU config & x86_64, but on other machines it may use something else for example a framebuffer. VGA mode 3 is a common x86/x64 choice, especially for older machines, but modern ones may not support it at all. - The reason it printed 3 "H" letters and not "Hel" is that I recycled the same command that I used to modify the first letter to red, and only changed the color so it brought over the same first letter each time.

This video is a tutorial on: - How printf works in the kernel - How to the debug the kernel with GDB - An intro into how to to use GDB - A guide on how to look up kernel documentation And several things more. Condensed in 12 minutes. This is perfect!! I've never seen a video as good as this one explaining anything!

”we’re gonna have to dive in a little bit to the assembly”. What a madlad ❤

I always wanted to know kernel that deep 🙂

You're making one of the nerdiest linux videos I've seen on windows using MS edge...saying I'm confused is an understatement

no unnecessary talking, straight to the point, extremely well explained, this is why I pay for internet, thank you brother

The rabbit hole is much deeper than I was thinking!

this feels like i'm watching paid content for free

kys_write?? how rude...

WTF, bro just said. "I don't really like AT&T *assembly* syntax, so I'm going to intel *syntax*" This man is crazy

The magic behind a standard library function-and the POSIX system calls-is what every CS student would have wondered about for once. Thank you for making this video. It brought back memories of being curious about how a computer works.

This series of videos is awesome. Just explains and explores a low-level topic quickly and without any fluff.

Excellent video as always. Love seeing well-made low level computing content that does deep dives into while keeping it just dense enough to watch in your free time. I feel like many videos on this topic are always either way too short/simplified or way too long and drawn out. You always hit it on the head.

This is like a whole subject at uni in less than 15 minutes. Subscribed!

I don’t know why but the way you say ‘config’ sounds satisfying

I love the confidence in your voice , i wana be this confidence when coding .

Really fast paced and right to the point. New sub 🎉

I like the way you explain things. I also noticed that you are very good and very at ease with programming languages. I will look into more of your videos / media when i jump into c programming. thanks again

I just discovered this channel today, and with two videos that I have seen I feel that in half an hour I have learned more than what I learned in many classes at the university. Subscribed!

Have been looking for a channel like that for a long time, thank you!

Thanks man, really useful. Keep up the great work!

That was awesome, I'd love a full series of this

This is such a good reference video for anyone wanting to dive into the kernel

Came here to learn about the kernel, but instead got an intermediate GDB tutorial. I'm thankful, I'm a lot more interested in GDB than the Linux kernel, actually. As for the video mode, yeah, I remember programming assembly as a child, I know how that mode works. I produced several full screen vomits of blinking colors.

these videos are so cool and nerdy and the best of it you learn so much

We are going to need some more of that gdb magic you are doing. Nice video!

You're a freaking wizard, Nic. Great video! 👍😊

Very interesting insight! Great content, thank you sir

Excellent job and crazy skills 🤯

What happens when you have a console window, rather than raw VGA as your tty? How does it "know" that stdout is mapped to VGA in this case? is it done during process creation?

This video is insanely good, not many like these!

Finally found this vid. I clicked on a different one when seeing this in the periphery and was searching for it ever since.

Excellent information presentation 👌

thanks for another great video!

Love your videos!

Dang breh aside from just screen printing, I learned some gdb and vim. Lots of good stuff.

Great video!

this is an insanely good video.... thanks

You back!

Thanks a lot! I'm trying to grasp system calls and standard library for my own OS. I am always shocked by the complexity of the code in Linux kernel and the amount of knowledge and talent it required to write.

Damn the knowledge I got through this video is amazing

learns a lot, thanks!

Thank you! Good stuff

You are an absolute legend 🤯

This is such a good video

I use gdb a lot but somehow didn't know about the 'advance' command, I would put a breakpoint when I wanted to advance forward (that I had to delete or disable later). So that's nice, thanks :) It might be worth adding that the vga text mode is a very legacy functionality. Qemu still supports it since its very easy to use from software but I'm not even sure if modern gpus support that. I think all modern gpus support only a normal linear pixel frame buffer where you'd have to blit your font characters manually.

Amazing video But I have a question, all those boot logs before printing the H, how are those printed.

This is so cool, thank you

wonderful explaination ,

idk why, but this is fun to watch.

Great job, Thanks bro

wow i didnt expect displaying text to be so complicated, that's interesting

Amazing video! Linux kernel + gdb + qemu = ❤ I hope you manage to build more videos like this. =D Hardware and software interaction would be great. 😃

Thanks for such an amazing video.

Awesome, thank you

some cool gdb tricks I didn't know. But I think I'll use the tui/disassembly view instead of jumping to addresses

This is fantastic

That is deeper than I thought

It’s so interesting👍

this is why I love RU-vid

Well done.

essential things, nicely done. But IMHO you missed one point, how vga works (logical level), ie what the kernel write to the vga memory in order to see an 'H' on the screen. Anyway thanks for sharing.

Nice👌

I still don't know why the random modified memory appears on the terminal, but I've learned the basics of GDB, so that's something

Oh damn, I'm coming in for another "Neat!"

Yayyy

Thats a knowledge packed video. I understood it in parts. Is there any past video i need to see to better inderstand this one?

this channel is cracked

0:56 For the record: the `-j` flag stands for "jobs", and tells `make` how many actions it may run in parallel. It can generally make a complex build faster, up to the limit of the number of CPU cores you have. At least for me, the numeric argument isn't necessary and by just passing `-j`, "make will not limit the number of jobs that can run simultaneously".

Nice 🎉

How does this change in a terminal app in a desktop environment?

Why did it print 3 "H"? I tought it would continue with the other letters...

👍👍Thanks!

Nir please I want to know what you way to learn efficiently ? can you give me our method ? some tips ? . Great video thanks

Could you make a video about how to make a simple wayland-based window manager?

great!

I guess if you wanna keep the character value but only change the color, you do bitwise AND to the value, for example $r10w=$r10w & 0x2FF (for green color) right? Did GDB support this expression?

Nice

Can yolu create 64 bit bootloader with c and asm

would be cool to show how graphical virtual terminals work in low level too.

This man is making some of the most informative and interesting Linux videos on all of youtube... using Windows 10

شكرا لك

I'm fairly new to linux.. Can someone tell me what he did on 9:17, to split the screen??

9:17 How did you do the "term" thing?

AMZ!!! love it !!! THX U U is very handsome!!!! ❤❤❤❤❤❤❤❤❤❤

Can you start a series on deeo dive into Linux kernal ? (A real detailed one)

How do you split view with the browser so easily?

How did you get the linux terminal on powershell?

Bro. Are you operative system developer ? how the hell can I learn that stuffs ?. This is a serius question. What books did you read about this ?

Driver devs can get a lot of hate sometimes, but if it weren't for them, we wouldn't get to see the hard work of printf()!

❤❤❤😊

based

interesting

int(9, "hi there" )

personally, I'm used to the convenience of a visual IDE and debugger

Why is Linux using VGA mode 3 in 2024?????

Noob arch user : nooo you can't just run both windows and linux Chad Kernel dev : anyway I just opened Qemu on Linux from ssh windows

Please Make Linux With Based-Debian

i'm not judging you but, why are you using windows when you're very interested in linux?

debugging linux kernel on windows im having a stroke