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Re: Xen boot strangeness (Was: Re: [SOLVED] Re: Xen 4.18.5_20250521nb0 not ELF binary (Was: Re: EFI and Xen))



At Sun, 01 Jun 2025 07:16:18 +0700, Robert Elz <kre%munnari.OZ.AU@localhost> wrote:
Subject: Re: Xen boot strangeness (Was: Re: [SOLVED] Re: Xen 4.18.5_20250521nb0 not ELF binary (Was: Re: EFI and Xen))
>
>     Date:        Sat, 31 May 2025 13:24:33 -0700
>     From:        "Greg A. Woods" <woods%planix.ca@localhost>
>     Message-ID:  <m1uLSkr-00Mo5fC@more.local>
>
>
>   | though that would be secondary if there were support to configure a dump
>   | device after boot.  FreeBSD has had a dumpon(8) utility since 2.0.5.
>
> Of course NetBSD can do that, see swapctl(8) -D  and more commonly, the "dp"
> flag (like "sw" for swap, either one, or both, can be used in a "swap" type
> entry) in fstab.

Ah yes, sorry I meant to check if swapctl had a way to set dumpdev, and
I had a niggling thought it could but my sleep-deprived brain just
wanted to hit "send"....

> The only conceivable reason I can imagine for wanting to pass dumpdev
> via the boot loader would be if the kernel were crashing before getting
> init started (no chance to process fstab at all).

Indeed, but even that could be done, with about the same effectiveness,
with a "dump=" parameter on the kernel command line, and that works even
for a Xen dom0 where the boot loader can only pass such info to the
NetBSD kernel via the command line configured in /boot.cfg anyway....

While the window between where the kernel actually has enough stuff
configured to actually write a dump and where init is started is rather
small, there's considerably more going on with many user processes
starting and running between when init starts /etc/rc and when
/etc/rc.d/swap1 finally gets run where an interesting crash might be
more likely to occur.

--
					Greg A. Woods <gwoods%acm.org@localhost>

Kelowna, BC     +1 250 762-7675           RoboHack <woods%robohack.ca@localhost>
Planix, Inc. <woods%planix.com@localhost>     Avoncote Farms <woods%avoncote.ca@localhost>

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