On Wed, Oct 12, 2016 at 06:04:09PM -0700, Seth Arnold wrote:
> On Wed, Oct 12, 2016 at 02:20:31PM -0700, Steve Langasek wrote:
> > Are you proposing to do away with this auto-expansion capability?  If so,
> > this implies that:

> How often does this auto-expansion fail?

I have not heard of it failing.  This is a straightforward operation
involving resize2fs and a partition table change from the initramfs before
the system has booted.  This is the existing behavior within the core snap,
and has been exercised for some time.

> How much memory does it take?  How much time does it take?  (And do either
> of these scale with the destination size?)

I haven't measured either of these, but Oliver hasn't complained (aside from
the one recent bug where ubuntu-image would sometimes create the initial
ext4 filesystem with wrong options, leading to wrong resize times).  I'm
sure he would have let us know if this was causing noticeable delays on
first boot. ;)

These should always scale very well with respect to filesystem size, just as
ext4 itself does, as in every case we're only moving around a small bit of
filesystem structure.

> What happens if the image is written to e.g. an SD card that previously
> had data on the rest of it? Is there a risk that the old "garbage" is
> available to applications?

Only if there is a bug in the kernel's ext4 driver that allows reads of
uninitialized data.

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/
slanga...@ubuntu.com                                     vor...@debian.org

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