grub-mkrescue not producing correctly bootable image

[Overv]

Hi,

I have some simple kernel code that just writes hello world to the VGA memory in text mode right now.
I'm not interested in writing my own bootloader, so I decided to use GRUB.

I compile and link my kernel like this (it's only x86 assembly, no C):

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nasm -felf hellokernel.asm -o hellokernel.o
ld -T link.ld -o hellokernel.bin hellokernel.o

I followed the bare bones guide to make the binary bootable. I created the following file structure:

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iso
---boot
------grub
---------grub.cfg
------hellokernel.bin

The configuration looks like this:

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menuentry "hellokernel" {
    multiboot /boot/hellokernel.bin
}

I used the following command to produce my .iso file:

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grub-mkrescue -o hellokernel.iso iso

I then created a new VirtualBox virtual machine without a hard drive and mounted the .iso file as CD/DVD drive. Unfortunately I get the following output:

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FATAL: Could not read from the boot medium! System halted.

So I inspected the contents of the file by extracting it and only found the file structure shown above. It seems that GRUB is not even included in the output file! What could be causing this?

[Overv]

Turns out it's because 'grub-mkrescue' silently fails when there is no /boot/grub directory. This problem occured on the Debian VPS I was compiling on, but when running it on a normal Ubuntu install, it works fine.

It's not really a problem, but is there a way to manually install these required files or is there an equivalent command that isn't specifically designed to produce a rescue file for the local OS?

[xenos]

Instead of using grub-mkrescue you could also try this:

http://wiki.osdev.org/Bootable_El-Torit ... RUB_Legacy

It also works with GRUB 2 - in that case replace the stage2_eltorito with a GRUB image built with grub-mkimage, as shown in the floppy (!) section here:

http://wiki.osdev.org/GRUB_2

[sortie]

I recommend that you simple download the latest GRUB release and build it from source and install it somewhere convenient (such as --prefix=/usr/local/grub) and add that location to PATH. The needed boot files should be installed there so you can grub-mkrescue as far a I know. Otherwise check the command line options to grub-mkrescue as it allows you to use boot files from another location.

[darkinsanity]

Turns out it's because 'grub-mkrescue' silently fails when there is no /boot/grub directory. This problem occured on the Debian VPS I was compiling on, but when running it on a normal Ubuntu install, it works fine.
or is there an equivalent command that isn't specifically designed to produce a rescue file for the local OS?

I'm using this script to create an ISO-image with GRUB 2 on it and it worked fine on all systems I tried (Ubuntu, Debian 7, Arch). I don't know if it works when /boot/grub is missing, though.

[xenos]

I'm using this script to create an ISO-image with GRUB 2 on it and it worked fine on all systems I tried (Ubuntu, Debian 7, Arch). I don't know if it works when /boot/grub is missing, though.

Well, this part of the script relies on /boot/grub (or in this case actually /grub, because of the -p switch) to exist, because it looks for the GRUB2 modules in that directory, from which it builds the GRUB2 image:

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grub-mkimage -p /grub -o core.img -O i386-pc biosdisk iso9660 multiboot configfile

[darkinsanity]

Well, this part of the script relies on /boot/grub (or in this case actually /grub, because of the -p switch) to exist, because it looks for the GRUB2 modules in that directory, from which it builds the GRUB2 image:

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grub-mkimage -p /grub -o core.img -O i386-pc biosdisk iso9660 multiboot configfile

The -p doesn't tell grub to search for the modules in that directory (that would be -d), it sets the prefix for the ISO-Image because boot.img and grub.cfg will be located in the grub-directory of the image. Also I have tried out the script a few minutes ago while there was no /boot/grub and it still worked, so I guess that grub-mkimage takes the modules from /usr/lib/grub/i386-pc (just like it says when you execute "grub-mkimage --help").

[xenos]

Yes, indeed - I was confusing the -d and -p switches... Actually I'm using a quite similar script to create a bootable CD image.