Re: [atomic-devel] EC2 PV/HVM AMIs

[Andy Grimm <agrimm gmail com>]

On Mon, Jul 21, 2014 at 4:25 PM, Matthew Miller <mattdm mattdm org> wrote:
> On Mon, Jul 21, 2014 at 02:33:55PM -0400, Andy Grimm wrote:
>> Fedora isn't going to stay this way for long, though  They are
>> intending to register HVM images.  Actually, I do not believe that
>> hvc0 is the correct console device for HVM images (I will double-check
>> this), and there is no issue specifying more than one console device.
>> The most recent RHEL 6 HVM image I registered specified "console=tty0
>> console=ttyS0 console=hvc0" just to cover all the bases.  I don't know
>> which of them was right, but I got console output.  :)
>
> There is, or was -- I haven't rechecked -- a bug where specifying
> non-existent console devices caused systemd to spawn a getty for them
> anyway, and possibly out of control.

ouch, that's not good.  I was not aware of that one.

> Also, when multiple consoles are listed, output goes to them all, but input
> comes from the last one. And, only last one is "/dev/console", which means
> that programs which open and write to /dev/console (cloud-init, I'm lookin'
> at you) are sensitive to the ordering here.

This is really interesting.  In the image I'm currently testing (which
is EL6, but that shouldn't matter for this particular point), I listed
"console=hvc0 console=ttyS0 console=tty0".  Everything I've found in
random blog posts suggests that the correct console device for HVM
images in EC2 is ttyS0, but tty0 is the one I have listed last, and
I'm getting cloud-init output.  I am more certain that hvc0 is *not*
the right device, since attempts to write to it under HVM return "No
such device or address".

> All of this might eventually mean that we need to eventually suck it up and
> generate tailored images for each environment -- we'd been wanting to avoid
> that, because it saves QA for us _and_ for users.
>
> In any case, consider this a big, waving "help wanted" flag. :)
>
> --
> Matthew Miller            mattdm mattdm org             <http://mattdm.org/>
> Fedora Project Leader  mattdm fedoraproject org  <http://fedoraproject.org/>