fromiso: DE: laufwerk "loop" nicht gefunden; EN: drive loop not found

[michaa7]

DE:
Beim versuch ein siduction iso (sowohl xorg december als auch xorg indiansummer) zu starten bekomme ich nach auswählen im grub menü nur soetwas wie:

Fehler: laufwerk "loop" nicht gefunden
Fehler: sie müssen zuerst einen kernelladen
(oder so ähnlich)

update-grub findet die isos, der pfad in /etc/default/grub2-fll-fromiso ist also wohl richtig. Aber ich kann mich nicht erinnern jemals selbst ein loop laufwerk eingerichtet zu haben. Was möchte mir dieser fehler also sagen?

EN:
On my new assembled computer (siduction xorg-december installed works fine!) I can't get to boot siduction*-iso. After selecting an *.iso in the grub2 menü I get something like:

Error: "drive "loop" not found
Error: you need to first load a kernel"
(or the like)

So it seems grub2 does not find something. But the thing is "update-grub" does not complain. So I wonder how the path to the *.iso_s is right for "update-grub" but wrong for Grub2? Or do we still need an extracted kernel in folder containing the iso (manual does not mention a kernel anymore)?

grub2-fll-fromiso

# Defaults for grub2-fll-fromiso update-grub helper
...
FLL_GRUB2_ISO_LOCATION="/media/disk1part3/sidon"

...
FLL_GRUB2_ISO_PREFIX="siduction-"

...
FLL_GRUB2_LANG="de_DE"

...
FLL_GRUB2_TZ="Europe/Berlin"

...
FLL_GRUB2_CHEATCODE="quiet noeject"

grub.cfg (relevant part):

### BEGIN /etc/grub.d/60_fll-fromiso ###
menuentry "siduction-13.2.1-december-xorg-amd64-201401272217 (vmlinuz0.amd)" {
        insmod iso9660
        insmod part_msdos
        insmod ext2
        set root='hd0,msdos3'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos3 --hint-efi=hd0,msdos3 --hint-baremetal=ahci0,m
sdos3 --hint='hd0,msdos3'  3axxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxd21
        else
          search --no-floppy --fs-uuid --set=root 3axxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxd21
     fi
loopback loop /media/disk1part3/sidon/siduction-13.2.1-december-xorg-amd64-201401272217.iso
linux (loop)/boot/vmlinuz0.amd fromhd=UUID=3axxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxd21 fromiso=/media/disk1part3/sidon/siducti
on-13.2.1-december-xorg-amd64-201401272217.iso boot=fll lang=de_DE tz=Europe/Berlin quiet noeject
initrd (loop)/boot/initrd0.amd
}
menuentry "siduction-14.1.0-indiansummer-xorg-amd64-201411230441 (vmlinuz0.amd)" {
        insmod iso9660
        insmod part_msdos
        insmod ext2
        set root='hd0,msdos3'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos3 --hint-efi=hd0,msdos3 --hint-baremetal=ahci0,m
sdos3 --hint='hd0,msdos3'  3axxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxd21
        else
          search --no-floppy --fs-uuid --set=root 3axxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxd21
        fi
loopback loop /media/disk1part3/sidon/siduction-14.1.0-indiansummer-xorg-amd64-201411230441.iso
linux (loop)/boot/vmlinuz0.amd fromhd=UUID=3axxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxd21 fromiso=/media/disk1part3/sidon/siducti
on-14.1.0-indiansummer-xorg-amd64-201411230441.iso boot=fll lang=de_DE tz=Europe/Berlin quiet noeject
initrd (loop)/boot/initrd0.amd
}
### END /etc/grub.d/60_fll-fromiso ###

The error seems somewhere in the logic used by update-grub when creating these entries.
'hd0,msdos3'  3axxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxd21 and /media/disk1part3/sidon/* don't fit, because on 3axxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxd21 there is no "/media/disk1part3". But this partition contains "/sidon" (the isos are on a separate partition mounted @ /media/disk1part3 when the installed main system on 'hd0,msdos1' is booted. But this path obvioulsy does not exist outside the system partition.
There seems to be some confusion how to compose those paths grub uses. It used to work on my old computer which was set up in the same way. So I really wonder what has changed in the meantime. Did I mess up something?

[michaa7]

To me it seems there are two different problems involved:

1)
the logic used by update-grub is somehow flawed. Here on my system it fails to create the right path when I use /media/disk1part3/sidon in grub2-fll-fromiso. The partition in this case is mounted via "mount /dev/sda3  /media/disk1part3". The resulting path in grub.cfg is /media/disk1part3/sidon/*, which is wrong.

But update-grub creates the right path if I use /dtn/soft/sidon in grub2-fll-fromiso. /dtn is where I mount my labeled partitions (LABEL=soft). In this case update grub in grub.cfg creates the  path sidon/* which is right.

In both cases I activated the respective entry in /etc/fstab before issuing "update-grub" (in case it would matter).

2)
But still it won't boot. I have no clue how it is supposed to work following the instructions given in the manual, here it does not work like described there. I needed to copy a (recent random) kernel together with it's initrd to /sidon to finally get an iso to boot.
Here real problem seems to be the (in my case wrong) assumtion "root" for the kernel and "root" for the directory the isos are stored in are the same.