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Bug#534887: live-initramfs: Loop mounting .iso for booting from multi-purpose USB stick?

On Sun, Jun 28, 2009 at 11:27:30AM +0200, Michael Prokop wrote:
> * Philip Hands <phil@hands.com> [20090628 01:25]:
> > I've been trying to build a versatile USB stick, with the imntent that
> > it be able to choose between various images at a grub prompt.  Some
> > .iso images (i.e. http://partedmagic.com/) are happy with this setup,
> > becasue once booted (via grub4dos's ability to map a .iso and boot it)
> > they look around for the image they came from and loop mount it, in much
> > the same way as debian-live looks for its .squashfs
> > debian-live does not appear to have this ability at present, although
> > given that it can find the .squashfs I'd guess it's not going to be
> > too hard to add, but I'm afraid my cursory glance over the code did not
> > reveal the place where it should be added.
> http://git.grml.org/?p=live-initramfs-grml.git;a=blob;f=debian/patches/06_support_fromiso_isofrom.dpatch;hb=HEAD
> http://git.grml.org/?p=live-initramfs-grml.git;a=blob;f=debian/patches/07_support_findiso.dpatch;hb=HEAD
> should basically do what you want.

Yup, I've tried applying them to the live-initramfs from debian's git,
and as long as I specify fromiso=/debian-live.iso (and call the image
that, of course) it works.

BTW would it not be a good idea to insert a / in front of the $FINDISO's
in the script, so that people don't have to remember it on the kernel
command line?

> Do I understand it right that the partedmagic live system doesn't
> require *any* additional bootoptions at all to boot the ISO directly
> from USB (running losetup & CO on it's own)?

Yes.  Again you need to name the image as it expects (which in the case
of PartedMagic 4.2 turns out to be "pmagic-4.1.iso", amusingly)

> [...]
> > There is at least one gotcha though -- grub will often fail to map an
> > image if it's fragmented, so you're liable to have to copy all the images
> > off the stick, delete them and then write them back to make it happy.
> > The --mem option to grub's map command is supposed to handle that case,
> > by copying the image to ram, but I've not had a lot of luck with that.
> > Note that when I say grub here I'm talking about grub4dos which is pretty
> > much the same as grub2, but seems to deal with the vagaries of USB-ZIP
> > rather better than grub2 at the moment.
> You mention it in your blog article
> http://wiki.hands.com//howto/ultimate-usb-stick/#gettingdebian-livetorun
> already, but JFTR: grub2 with loopback option doesn't have the
> fragmentation problem (though grub2 was/is kind of broken in current
> Debian/unstable).
> What systems do you have that support USB-ZIP only?

The one that prompted me to go to the effort was a recently purchased
Jetway JNC91-330-LF 1.6GHz Dual Core ATOM Mainboard, which came with
Pheonix AwardBIOS 6.00PG Copyright --2008

Oh, damn ... /me btters his head against the desk for a little while...

Right, prompted by your question, and the fact that the system in
question really ought to know how to boot USB-HDD, I had another rumage
through the boot options.

The menu for booting mentions USB-FDD USB-ZIP and USB-CD, but no USB-HDD.

Of course, the thing that I'd failed to spot was the little arrow next
to the "Hard Disk" option, indicating the presence of a sub-menu.

If one selects that sub-menu, it reveals an option for the built-in HDD,
and a "Bootable Add-in Cards" option -- which is what I was after all
along, it seems.

Ho hum -- I suppose I can make my usb-stick setup considerably less
complicated now :-)

Cheers, Phil.

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