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Add files to bootable Linux CD ISO image...?

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  • esuhl
    esuhl Posts: 9,409 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    edited 7 August 2018 at 10:50PM
    Have you tried in a 32bit environment ? just an idea:D

    I tried on an old 32-bit laptop, and the boot process stalled, whilst accessing the empty CD tray, with the message:
    Looking for CDROM in: /dev/hdc1
    
    I ejected the CD tray, and the PC continued "brute force" scanning for other partitions of other letters/numbers (hdc10,hdc11,hdc12,etc.) , before displaying the same message (as above) about not finding the KNOPPIX filesystem.

    The USB stick isn't even detected as being bootable (by the BIOS) on one of the PCs that I want to run it on anyway. :-/
  • psychic_teabag
    psychic_teabag Posts: 2,865 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Combo Breaker
    edited 8 August 2018 at 11:03AM
    esuhl wrote: »
    The on-screen messages end with:
    UDF-fs: No partition found (1)
    XFS: bad magic number
    XFS: SB validate failed
    Kernel panic: VFS: Unable to mount root fs on ram0
    
    But that was trying to boot the CD contents without unsquashing the rootfs. Is that barking up the wrong tree?

    Googling for that... in one case, someone fixed it by removing the initrd parameter from the boot cmd line. I'm afraid I don't know enough about how the kernel finds rootfs to be able to help much... if it's a squashfs, there must be some way to tell it that the squashfs has to be mounted loopback from within another filesystem - all that is presumably happening inside the initrd.

    Unsquashing the rootfs to a simple ext2 filesystem may remove the need for an initrd at all - the kernel can presumably find a simple partition without any assistance.
    Is it time to accept that booting this CD from hard drive just isn't possible?

    It's possible. Just depends how determined you are, and how much patience you have ;-)

    Ah - I've had another look at the image... /isolinux has a miniroot.gz which turns out to be a compressed ext2 image. Uncompressing and mounting that, it turns out that it has soft links back out to /cdrom/KNOPPIX things. Presumably this miniroot is the thing that uncompressed into ram and then mounted as the temporary rootfs.

    linuxrc is a shell script which drives all the startup - that's the thing that's presenting the message you saw about the very limited shell when it couldn't find what it was looking for.

    https://en.wikipedia.org/wiki/Linux_boot might be helpful, if you haven't seen it.
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