loop-mounted ISO images

[<ian_bruce@fastmail.net>]

Is there some boot parameter that can be given to the Debian installer
initrd to make it understand that it's running from a loop-mounted ISO
image file rather than a plain block device?

This is a well established feature in some distributions; for example,
in Ubuntu, the relevant parameter is "iso-scan/filename=<FILENAME>".

However, looking through the Debian initrd doesn't find anything that
seems relevant:

    $ zcat /mnt/debian-7.1.0-amd64-i386-netinst/install.amd/initrd.gz |
        strings |
          grep -E -i \
            -e '(iso|img|image).*(scan|loop|file|path|from|boot)' \
            -e '(scan|loop|file|path|from|boot).*(iso|img|image)'

    Description: ISOFS filesystem support
    __isoc99_sscanf
                    # BOOT_IMAGE is added by syslinux
                    if [ "$var" = "BOOT_IMAGE" ]; then
    __isoc99_sscanf
    __isoc99_sscanf
    __isoc99_vsscanf
    Failed to open bios image file
    Image file size Error
    <7>ISOFS: Interleaved files not (yet) supported.
    <7>ISOFS: File unit size != 0 for ISO file (%ld).

The instructions here would seem to suggest that no such paramater is
needed, that the initrd can figure this out automatically:

http://www.debian.org/releases/stable/amd64/ch04s03.html.en#usb-copy-flexible

However, if this is the case, how does it decide which ISO file to use
if there is more than one present?

The point of all this is, of course, to create a USB flashdrive with
multiple distribution ISOs installed on it, selectable at boot time.

http://sourceforge.net/projects/multibootusb/


-- Ian Bruce