Re: Any way to boot Guix with root partition elsewhere?

[Jonathan McHugh <indieterminacy@libre.brussels>]

A shot in the dark - but I know that there have been some activity with
regards to using Lua in the kernel:
=> https://github.com/luainkernel
=> lwn.net/Articles/830154/

If thats not helpful hopefully it can give you some ideas.

Has Guile done much activity interacting with the kernel?


Jonathan


Vladilen Kozin <vladilen.kozin@gmail.com> writes:

> Well, I went ahead and asked the help-grub@gnu.org but I'm thinking it
> maybe difficult or impossible to solve. There may actually be the
> "Guix" way to solve this. Here are my current thoughts.
>
> Problem (not specific to Guix):
> - we install Guix onto NVMe SSD drive that's plugged via PCIe adaptor,
> - BIOS doesn't make those available to boot,
> - so you can't boot directly off of that SSD,
> - but worse, Grub on any visible drive e.g. USB won't find that SSD either.
>
> IIUC what "solutions" I've seen, they amount to booting off e.g. USB
> stick where you have your /boot/grub with grub.cfg BUT with actual
> kernel and initrd you want to boot copied over from that SSD drive AND
> with whatever kernel parameters your installation suggested. So, I
> think roughly this amounts to copying your Guix system's current
> kernel and initrd over to USB stick as well as its /boot/grub/grub.cfg
> and maybe tweaking it a bit to point to this copied kernel. Or smth
> like that.
>
> This obviously defeats the main value proposition of Guix, cause
> suddenly no "boot into another system instance", no "roll back".
>
> IMO good solution would be to have Grub load just enough of whatever
> kernel is doing to find that drive and make its contents available. I
> doubt one can do that, but maybe one can boot into some kernel and
> initrd and then "chain" load the Grub on that SSD? I've no clue how to
> do that, but I'm sure its possible: kernel is code running in memory,
> surely it can "load" and "pass control" over to Grub or smth. If
> anyone knows, do tell.
>
> Guix way of solving this could be by coding the above step explicitly
> into your config.scm, so that your `guix system reconfigure` having
> built everything, copies new kernel and initrd over to USB drive in
> addition to earlier kernels etc along with appropriate grub.cfg
> (essentially mirroring that bit of your OS on the SSD). Brittle, but
> at least you have your earlier systems etc etc.
>
> The whole "boot" business is at the edge of my understanding of how
> systems bootstrap and OMG this whole territory is full of arcane
> sacred knowledge spread all over the interwebs and most of what you
> find is nonsense. Once people who actually know how the sausage is
> made retire or die, our civilization is doomed :(
>
> On Sat, 1 May 2021 at 04:07, Joshua Branson <jbranso@dismail.de> wrote:
>>
>> Vladilen Kozin <vladilen.kozin@gmail.com> writes:
>>
>> > Hello guix.
>> >
>> > Is there a way out of this predicament? I can see two options.
>> > (1) can some Linux distro/bootloader do the FreeBSD trick: start on
>> > USB but then chain-boot Guix off that SSD? IIUC grub's chain-boot is
>> > of no help here, cause it simply won't even see that drive;
>> > (2) install and run Guix off USB but somehow ensure that "IO heavy"
>> > bits are mounted from that SSD. There's gotta be some (file-systems
>> > ...) combined with the way I `guix system init config.scm /mnt` (or
>> > rather what else I mount under /mnt where) that would achieve this?
>>
>> Hmm. I'm way out of my depth here...
>>
>> I think number 1 is your "best" bet.  I've no idea how to do that.
>>
>> Number 2 is probably your "easiest" option.  /boot/ should be put on the
>> usb, and I suppose that the / should be on the SSD...You would install
>> this way.  That's probably how I'd do it.  Or rather that is how I would
>> try to do it.  :)
>>
>>
>> This is probably a silly idea...would linuxboot.org help?  You use linux
>> to boot?
>>
>>
>> Another silly idea...could you embed linux in your flashrom?  I think
>> that osboot.org is planning on embedding linux in the flashrom...That
>> would be pretty awesome.  My flashrom is only 8MB though...
>>
>>
>> Best of luck!
>>
>> Joshua
>>
>> --
>> Joshua Branson (joshuaBPMan in #guix)
>> Sent from Emacs and Gnus
>>   https://gnucode.me
>>   https://video.hardlimit.com/accounts/joshua_branson/video-channels
>>   https://propernaming.org
>>   "You can have whatever you want, as long as you help
>> enough other people get what they want." - Zig Ziglar


-- 
Jonathan McHugh
indieterminacy@libre.brussels