GPT boot has less features than legacy MBR-based one (Was: UEFI, loader.efi and /boot.config)

[Karl Denninger]

On 1/19/2019 10:32, Rodney W. Grimes wrote:
>> ......
> The BIOS does NOT do what our boot0 does, I have seen no BIOS that
> well allow me to select a partition on a drive, you can only select
> the drive.
>
> I think this is the feature that Lev is missing, and I am sure
> others shall miss it to.
>
> IIRC whistle used a version of this so you could install a new system
> to partion 2, keeping your current system in partion 1, and changing the
> active back and forth.  If we have lost that basic functionality with
> the growth of GPT and UEFI that is a sad day.

It is indeed, especially for embedded applications.

I really, really like the fact that NanoBSD (on an MBR boot) can have
two partitions and mark the "other one" as active; this then lets you
update the code "in place" and as long as you are paying attention to
what goes into the volatile overlays (specifically although not
exclusively don't let /etc/fstab with a hard-coded filesystem reference
get into there!) then you can "warm update" a running system and reboot
into the new code.

If something goes wrong re-marking the old partition active is not
terribly hard, so there's a *reasonable* recovery path available.

I've not found a reliable way to do that sort of thing with many of the
"newer" small-board devices and I really like it on, for example, my
apu2 firewall appliances that I and others are using all over the place
in that being able to put together a code-fix update is of material value.

-- 
Karl Denninger
karl at denninger.net
/The Market Ticker/


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