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necromancer_df

Extract cd boot image

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Does anyone know how to extract the boot image from a bootable cd in linux? I've heard it's not as easy as just DDing off the first 1440k. Any ideas? Extensive googling hasn't turned up much, just windows tools to do it and references to the el-torito spec. Maybe i'll have to read the el-torito spec and figure it out myself :S edit: neglected to mention i need to do it in linux [Edited by - necromancer_df on May 21, 2006 2:43:00 PM]

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Did you mount the cd and look for somethng called /boot/initrd-xxx.img or something like that?

I think the boot image is usually called initrd...
But I dont know how the boot process locates it though

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Quote:
Original post by pulpfist
I think the boot image is usually called initrd...
But I dont know how the boot process locates it though


The bootloader knows it. If you're using GRUB, check /boot/grub/menu.lst. I don't know what most Live CD's use but it's probabely either GRUB or LILO.

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Most bootable Linux CDs use either LILO, GRUB, or isolinux. The LILO and GRUB bootloaders actaully boot what they think is a floppy image, and it's likely found at a place on the disk starting with /boot (this is not a requirement, just a convention). It's likely a plain, readable filesystem file that's a floppy image you can mount using the loopback driver.

The isolinux bootloader boots directly off the CD (no floppy emulation, meaning it will boot bigger kernels and have more driver modules loadedable, which means better hardware support). You can google for isolinux to get more information.

It's likely that the more up-to-date distros use isolinux becuase of the latter-day kernel size and variety of drivers to load for a live CD filesystem. I know at least one commercial distro does, or at least will in their upcoming new release.

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Thanks for the replies. I'm actually trying to get the boot image off a Windows cd using linux tools. Sorry for not mentioning that before.. The reason i'm doing this is to create a customised Windows XP install CD that contains my SATA drivers (google for windows xp slipstream) so i can actually install it on my system that doesn't have a floppy drive. I could fork out £10 on a floppy drive but that would be a last resort.

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