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Thanks for Scott, Padraig, Juerg. I have the whole image of this feature.
But, who knows what's the implementation in AWS cloud when using RHEL OS?


On Wed, Mar 6, 2013 at 9:15 AM, Joshua Harlow <harlowja at yahoo-inc.com>wrote:

> +1 I think cloud-init can do this all in a more correct manner and in a
> manner that works across more distributions and file system types in the
> long term.
>
> On 3/5/13 5:08 PM, "Scott Moser" <smoser at ubuntu.com> wrote:
>
> >On Wed, 6 Mar 2013, Pádraig Brady wrote:
> >
> >> On 03/05/2013 02:04 PM, Scott Moser wrote:
> >> > On Tue, 5 Mar 2013, Sylvain Bauza wrote:
> >> >
> >> >> If you look at
> >> >> http://www.pixelbeat.org/docs/openstack_libvirt_images/#1361764412,
> >>you'll see
> >> >> that resize2fs is performed. But there is a caveat with RHEL6 which
> >>is Linux
> >> >> 2.6 (contrary to Ubuntu 12.04 which is Linux 3.0).
> >> >> If you look at "man resize2fs" :
> >> >
> >> > Please don't do this, or rely on this.  Having the hypervisor do this
> >>for
> >> > your guest is simply wrong.  Hypervisors should know little to nothing
> >> > about the internals of the instances they're launching.
> >>
> >> Just to point out the alternative for when the VM doesn't
> >> have the smarts to resize itself, is to use something like virt-resize:
> >> https://blueprints.launchpad.net/nova/+spec/resize-no-raw
> >
> >
> >Using libguestfs is worlds better than having the host "directly" do it.
> >But really whats happening here is *still* something with very little
> >information mucking with (and possibly breaking) the inside of a disk
> >image.  The more we consider that a "bucket of bytes" the better.
> >
> >If you are using libguestfs, chances are you're using it from your distro,
> >and patching it to deal with a new filesystem (or otherwise get the update
> >to your hostOS) is still problematic.
> >
> >Just let/expect the guest do it, and we'll avoid a whole silly game of cat
> >and mouse that doesn't even have to be played.
> >
> >When was the last time you updated your bios on your laptop so you could
> >use a new linux filesystem?  That sounds silly, doesn't it.  Having
> >openstack reach inside the contents of the disk is just as silly.
> >
> >One of the major benefits of having cloud-init direct the partition resize
> >*and* subsequent filesystem resize is that the user can (in user-data)
> >disable this!  (currently the initramfs doesn't take any instruction from
> >user-data, so disabling it isn't really a possibility).  perhaps they
> >didn't want that extra instance-store space to be part of the root
> >filesystem.
> >
> >If you put that function inside the hypervisor, you either can't do it, of
> >you have to expose some silly api-launch parameter of
> >"do_not_modify_disk".  It complicates the API and complicates the host.
>
>
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-- 
Lei Zhang

Blog: http://jeffrey4l.github.com
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