Re: [CFT] bsdinstall and zfsboot enhancements

From: Teske, Devin <Devin.Teske_at_fisglobal.com>
Date: Mon, 11 Nov 2013 20:40:53 +0000
On Nov 11, 2013, at 12:35 PM, Nathan Whitehorn wrote:

> On 11/11/13 14:30, Teske, Devin wrote:
>> (disabling default gpg-signing until they fix a bug with the quoting)
>> 
>> On Nov 11, 2013, at 11:46 AM, Michael Dexter wrote:
>> 
>>> Hello all,
>>> 
>>> I have been experimenting with various BSD and GNU/Linux boot media
>>> under bhyve and noticed that we may want to accommodate the "LiveCD"
>>> mode of the installer, which in turn requires the correct console.
>>> 
>>> Currently, one is prompted for VT100 for installation but this does not
>>> appear to work/stick for LiveCD mode.
>>> 
>>> Can anyone verify this?
>>> 
>> Sorry, I mistook your issue in the previous e-mail to be on-going with the
>> thread it was inline with.
>> 
>> "LiveCD" changes things a bit.
>> 
>> (thinks)
>> 
>> I would expect that a prompt could do:
>> 
>> 	1. modify /etc/ttys on the boot media
>> 	2. run "init q"
>> 
>> But there's a couple of assumptions...
>> 
>> 	3. Can we even write to /etc/ttys?
>> 	NB: We can write to /tmp because it's an md0 swap device
>> 
>> So do we have to get fancy with slipping a unionfs layer backed by another
>> md swap device above the root?
>> 
>> That would make every file on the boot media writable (writes would go to
>> the swap-backed md device and if you execute "rm -fW file" you can get back
>> files that have been previously unlinked -- unlinks are stored as whiteouts in
>> the swap backed md device). For all intents and purposes, the read-only file-
>> system becomes writable and we could then munge /etc/ttys to enable serial
>> only when a menu item is chosen.
>> 
>> If I'm off-base, let me know... sounds like a lot of trouble.
>> 
>> The alternative being that you enable serial by default but then I have to tell
>> field engineers to unplug barcode readers before they do an install??? (that's
>> a question, it may be entirely safe, but I've never tried, seems unsafe)
>> 
>> Question is, how would you disable it? Goes back to writable filesystem.
> 
> This is why I don't think we want to modify /etc/ttys. Instead we want to have init do the right thing (follow the boot console) with a single unchanged /etc/ttys.

Let me see if I've got it right...

Already-knowns:
+ The boot variables are influenced by loader.conf which is read-only media.
+ But Michael is loading the media from bhyve.

Question:
Does bhyve set kern.console irrespective of loader.conf values?

If so, then yeah... I'm all for supporting your stated Option-A in the other thread.
-- 
Devin

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Received on Mon Nov 11 2013 - 19:42:04 UTC

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