CODEWITHSUNDEEP
ubuntuassemblyvirtualboxosdevgrub
user9643348
user9643348

Reputation:

How to make a "Hello world" kernel

I followed this article on how to make a very simple kernel which prints "Hello, World". The files to my project are available on Github.

I built my cross compiler from this project. I use these command to cross compile, assemble, and build my ISO (CD-ROM image):

i686-elf-as boot.s -o boot.o
i686-elf-gcc -c kernel.c -o kernel.o -std=gnu99 -ffreestanding -O2 -Wall -Wextra
i686-elf-gcc -T linker.ld -o myos.bin -ffreestanding -O2 -nostdlib boot.o kernel.o -lgcc
mkdir -p isodir/boot/grub
cp myos.bin isodir/boot/myos.bin
cp grub.cfg isodir/boot/grub/grub.cfg
grub-mkrescue -o myos.iso isodir

When I tried to execute it on VirtualBox, it gives the following message:

FATAL: No bootable medium found! System halted.

Why am I getting this error, and how can I fix it?

P.S. I use Ubuntu subsystem for Windows 10

Upvotes: 1

Views: 1512

Answers (1)

Michael Petch
Michael Petch

Reputation: 47573

Likely there is a GRUB component missing or an incorrect version of Xorriso. In the Bare Bones article you linked to it says this:

You can easily create a bootable CD-ROM image containing the GRUB bootloader and your kernel using the program grub-mkrescue. You may need to install the GRUB utility programs and the program xorriso (version 0.5.6 or higher).

When using grub-mkrescue to make ISO images, more often than not unbootable ISOs is a result of Xorisso installation missing. If grub-mkrescue runs but doesn't produce ISOs at all then likely a GRUB component is missing. To ensure that you have all the GRUB and Xorriso components installed install the components on modern Ubuntu releases with:

sudo apt-get install grub2-common grub-pc xorriso

Then attempt to rebuild and rerun your ISO image in VirtualBox.

Upvotes: 1

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