Re: Kernel selection in Lua loader

On Wed, Feb 21, 2018 at 6:11 AM, Kyle Evans <kevans_at_freebsd.org> wrote:
> On Wed, Feb 21, 2018 at 6:36 AM, David Wolfskill <david_at_catwhisker.org> wrote:
>>
>> ...
>> kernels="kernel kernel.old kernel.save"
>>
>> and the Forth loader presented (precisely) those kernels as the
>> available options for selecting a kernel to load and boot.
>>
>
> Right, so, we (and by we I mean cem_at_) actually implemented a form of
> auto-detection for kernels. Any directory in in /boot with a file
> named 'kernel' inside will be automatically listed, and that
> supplemented(*) 'kernels' and 'kernel' specified in loader.conf(5).
>
> (*) I use "supplemented" because I changed that in r329709, just a
> little bit ago, to not do the autodetection if a 'kernels' is
> explicitly set in loader.conf(5) My reasoning here is that there's
> probably a reason one has set it explicitly, whether it be to hide
> bogus kernels or just to slim down the list of kernels they need to
> cycle through.

Yep.  And to add a little more detail, because I like this behavior,
I've convinced Kyle to add a knob to re-enable the autodetection
behavior even in the presence of kernels="", by adding a
kernels_autodetect="yes" knob to loader.conf (r329733).

Note that any kernels in kernels="" are offered first in the list, in
the same order as configured; any additional autodetected kernels
follow at the end (as you observed earlier):

>> with the Lua loader, I was being offered a choice among 4 kernels
>> (rather than the expected 3).  Cycling through them (twice; I wanted
>> to be sure the behavior was reproducible), I noted that the presented
>> options were:
>>
>> * default/kernel
>> * kernel.old
>> * kernel.save
>> * kernel.panic
>>
>> (in that sequence).

Best,
Conrad