Bochs cdrom

[mobruan]

Hi, how do i boot in bochs from a cd-rom?
Thanks

[Troy Martin]

Well, if you're using a physical CD, put in into your CD drive and edit your bochsrc config file to have something like this in it:

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ata0: enabled=1, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
ata0-master: type=cdrom, path="x", status=inserted

Where "x" is the name of the drive that has the CD in it. Change your boot: something line to boot: cdrom and save it. It should boot now. I haven't used Bochs since 2.3.0 (mid-2006!)

[mobruan]

Hi, and if i want to boot from image?
Thanks!

[Troy Martin]

Replace the "x" with "imagename.iso" where imagename.iso is the filename of the image

[mobruan]

Hi, didnt work. I think i need a program to generate a cd-rom image. Now i´m only chance the extension of the archive to .img.
what do you think?
thanks

[Masterkiller]

Booting from CD is more complicated than booting a diskette. You should have a boot volume descriptor at sector 17 (or just somewhere between main volume descriptor in sector 16 and terminate descriptor). Boot volume descriptor points to special sector that describes LBA block from where to load, number of sectors to load and load address. Last two things are not always supported and load address is still 0x07C0:0x0000 (0x7C00) and only one sector is loaded (even only first 512 of the sector).
For more information click here: http://en.wikipedia.org/wiki/El_Torito_ ... _standard) and look somewhere in the external links.
.ISO file can be created manually (even using assembler). First 2048 bytes from the file are the first sector, secont 2048 are the second and so on.

[egos]

The standard provides boot block with size of 65535 512-byted sectors (usually just 4 sectors).

[mobruan]

Hi, if diskete is more easie i´ll try it. What i have to write in the config file to boot from a diskete image?
Thanks

[samueldotj]

Creating a grub bootable ISO is easy - see http://wiki.osdev.org/Mkisofs

[Walling]

I use a .iso image myself in my "reseach" OS. All virtual machines support booting it. I do that because I won't develop a file system driver soon (ISO9660 format is complicated I hear); instead I ask GRUB to load the modules I need. In that sense .iso images are really easy.

You need to get GRUB Legacy compiled for El Torito boot. It is a file called stage2_eltorito. If you're using Linux and have GRUB installed, just find it in /usr/lib/grub/i386-pc/stage2_eltorito. If you're using Windows, google the file. Create a directory for your .iso image content. I'll call it "iso". Then create the directory structure needed for GRUB:

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iso/
  boot/
    you-can-put-your-kernel-here
    grub/
      stage2_eltorito
      menu.lst

In menu.lst you write something like this:

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default 0
timeout 10

title My kernel
kernel /boot/you-can-put-your-kernel-here
module /foo/bar/module ...

You don't have to use the "root" command. When GRUB boots in El Torito mode, the root is already set to "(cd)". Now create the .iso image using mkisofs / genisoimage, like this:

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mkisofs -R -b boot/grub/stage2_eltorito -no-emul-boot -boot-load-size 4 -boot-info-table -o my_kernel.iso iso

That's it (beside adding the tasks to your Makefile). Boot it and enjoy.