[colug-432] creating sparse disk images

Chris Punches punches.chris at gmail.com
Mon Nov 12 20:32:41 EST 2018

You don't need a sparse file.  And you're telling dd to copy the whole disk
and that's what it's doing.  It's a 16GB card.  If you had partitions you
would refer to them as /dev/sdc{1..4}

To make an iso file from a directory you want to use something like

`mkisofs -o ${ISO_PATH} ${DIRECTORY}`

Keep in mind you still have no bootloader.  You'll want to install one if
you want to actually boot from that disk.  Grub2 is nice.


On Mon, Nov 12, 2018 at 5:41 PM Roberto C. Sánchez <roberto at connexer.com>

> On Mon, Nov 12, 2018 at 07:02:25PM -0300, Rick Hornsby wrote:
> >    A normal RaspberryPi image from Raspian is ~1.5GB as a zip, and as
> far as
> >    I can tell, around or about 4GB when expanded and burned to an SD
> card.
> >    I’m having a hard time taking the SD card and creating a sparse image
> from
> >    it. I think “sparse” is what I want — I burned the image to a 16GB SD
> card
> >    made some changes and then tried to use dd to create an image of the
> >    modified card, and no matter what I do I’m always ending up with a
> 16GB
> >    image file. The changes I made include installing a couple of
> packages, a
> >    couple of python modules, and setting up some python scripts to run
> as a
> >    service on boot. Nothing major.
> >    I’ve tried to run zerofree on the card (to ensure the free space is
> all
> >    0x00), and then specifying ‘conv=sparse’ to dd but it made no
> difference.
> >    I tried making the image on Linux and Mac. dd seems to be very
> similar on
> >    both.
> >    # dd if=/dev/sdc of=/tmp/sd_card.img conv=sparse
> It has been some time since I had to do something like this, but after
> creating the image with dd, you need you use something like rsync or
> qemu-img to turn the image into a proper sparse file.  I have used both
> and either one should do what you need.
> --
> Roberto C. Sánchez
> http://people.connexer.com/~roberto
> http://www.connexer.com
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