Message-ID: <8f1653ba-e803-4b1d-9403-4284e647c3df@pobox.com>
Date: Sun, 10 Nov 2024 13:38:11 +0000
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From: rptb1+alpine@pobox.com
Subject: A "diskless" Xen dom0 entirely in the ESP
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Hello.

I'm hoping for a bit of advice on how to proceed.

I'm interested in creating an Alpine Xen dom0 that runs entirely from 
the ESP partition (a.k.a. the EFI partition).  I believe this should be 
possible by combining a clean "diskless" installation with apkovl to 
provide configuration.  It doesn't really matter about the bootloader -- 
I can make Grub or xen.efi or EFISTUB work.  I'm wondering about the 
best way to achieve my goal.

It seems to me that I should be able to install the entire "diskless" 
Alpine in the initramfs.

The instructions at 
https://wiki.alpinelinux.org/wiki/Create_a_Bootable_Device seem to get 
*quite* close to what I want, but of course they are creating a bootable 
MBR partition, not an initramfs.

The boot sequence would be:

1. UEFI bios
2. bootloader (optional)
3. xen.efi
4. kernel
5. initramfs
6. init script
7. apkovl etc.

It seems to me that I might need to make a custom initramfs init script 
that *does not* pivot to another root filesystem, since the initramfs 
will *be* the diskless filesystem.

I'm writing to the mailing list to see if anyone else has achieved a 
similar result, even if in a different way.  Or if anyone has a 
different suggestion for how I might achieve my result.  Or any short 
cuts for this work.

It would be nice if the final system is able to upgrade itself without a 
lot of work, too.

The initramfs init script seems quite flexible, but I haven't found a 
way to convince it that it's living in a finished diskless installation.

Thanks!