livecd-iso-to-disk with file as target

Hi all,

Is there any way I can get livecd-iso-to-disk to do its thing with a 
target that is not a regular block-device?

I spin images regularly throughout the work day and then have to transfer 
the image to a CF or SD card using this tool, then drop said card into a 
host for each test cycle.  This is, of course, tedious.  I'd like to 
shorten the process by using a VM as the host and simply point this VM to 
a disk image file that I populate directly with livecd-iso-to-disk. 
Presently, the tool balks at my attempt complaining with the error that, 
"test.img is not a block device".

I already have used the VM to run the ISO directly, but that is 
insufficient for my use case because I absolutely need the persistent 
storage that usually is possible via the remaining space of the CF/SD 
card.  Yes, I could create a second virtual disk for the persistent 
storage, but that would require lots of retooling of my various OS hooks 
and arguably be sufficiently different to the normal deployment that it 
would be a weak test at best.

--
John Florian

> From: [e-mail]
>
> Is there any way I can get livecd-iso-to-disk to do its thing with a
> target that is not a regular block-device?
>
> I spin images regularly throughout the work day and then have to 
> transfer the image to a CF or SD card using this tool, then drop 
> said card into a host for each test cycle.  This is, of course, 
> tedious.  I'd like to shorten the process by using a VM as the host 
> and simply point this VM to a disk image file that I populate 
> directly with livecd-iso-to-disk.  Presently, the tool balks at my 
> attempt complaining with the error that, "test.img is not a block

device".
> I already have used the VM to run the ISO directly, but that is 
> insufficient for my use case because I absolutely need the 
> persistent storage that usually is possible via the remaining space 
> of the CF/SD card.  Yes, I could create a second virtual disk for 
> the persistent storage, but that would require lots of retooling of 
> my various OS hooks and arguably be sufficiently different to the 
> normal deployment that it would be a weak test at best.

After a bit of poking around in /usr/bin/livecd-iso-to-disk, I see 
getdisk() and isdevloop() which hinted at me (where the docs did not) to 
try the following:

# dd if=/dev/zero of=test.img bs=1G count=2
# losetup --find --show test.img
/dev/loop0
# livecd-iso-to-disk --reset-mbr --noverify my.iso /dev/loop0

After that completed I configured a libvirt VM with an IDE disk whose 
source path was /dev/loop0 and storage format was raw.  The VM booted and 
behaved perfectly as I'd hoped.

I'll have to play with this for a while to see if it can be made a bit 
less cumbersome.  Another option I toyed with was creating a logical 
volume to serve the same purpose as test.img here.  That was in fact how I 
wound looking at getdisk() because it chokes on logical volume type block 
devices and probably all virtual block devices from what I've seen.  If I 
put together a patch to allow this, would that be of interest to the 
livecd-tools project?

--
John Florian