ubuntu-image 0.7ubuntu1

[Steve Langasek]

On Tue, Oct 11, 2016 at 06:12:06PM +0200, Oliver Grawert wrote:

> Am Dienstag, den 11.10.2016, 11:55 -0400 schrieb Barry Warsaw:
> > On Oct 11, 2016, at 05:01 PM, Oliver Grawert wrote:

> > > defining it in the gadget would be rather awful since that means if we
> > > use an identical image for cloud, VM  and "normal PC install" we would
> > > need a gadget per image just for that one difference ...  (the pc
> > > image that you can use for all three consists of: pc (gadget,
> > > pc-kernel (obviously kernel) and core (rootfs).
> > That's the data point I was looking for, thanks!

> > Can you explain in more detail why kvm images need some extra space, but
> > other images do not?

> on VMs the img file defines the "physical VM disk" while for an actual
> install you write the img file to a pyhsical disk device ... the resize
> code will find that the partition table does not cover all of the disk
> before first boot and start the resize process so here the img size
> wont be taken into account at all.

> on a VM, all the resize code will see is the img file that pretends to
> be a harddisk and it will find there is nothing to resize to.

> > Also, if you specify a fudge factor via cli/envar, should that be
> > applied in addition to, or instead of, any built-in compensation for
> > file system overhead?

> i dont mind either, whatever is easier to implement (as long as the
> help documents the right behaviour) ;)

I don't think a 'fudge factor' option is particularly clean or intuitive.  I
think what you actually want is to be able to declare the overall size of
the image that you're building.  It's a waste of mental energy to think
about VM image sizes in increments less than 1G, especially given that these
are all still going to be sparse files.

So I would suggest:

 - a --size option to ubuntu-image to specify the full image size (needs
   some careful thought for the multiple-image case)
 - keep the 50% buffer on ext4 filesystem size as a floor (the '50%' can be
   refined over time with investigation into the actual size requirements
   for ext4 metadata, but this is not a high priority; highest priority is
   that it works reliably)
 - if --size is smaller than the minimum size needed to accommodate the
   contents, warn but build the image anyway - because all the expensive
   work of ubuntu-image happens /before/ we're able to calculate the final
   size, so throwing that all away at the end would be /very annoying/.

How does that sound?

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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