Moving Gentoo to another arch.

lekto · Posted: Mon Oct 03, 2022 1:22 pm Post subject: Moving Gentoo to another arch.

This is a theoretical question. I had a machine that worked as nas+router, I moved router part to separate machine and now I have the machine that works just as nas. Today, I realized that I could use my Raspberry Pi 4 8GB as nas (similar performance, lower power consumption and noise), but since this is different architecture I would need to reinstall whole system. Is there a way to move Gentoo from amd64 to arm64?
I think, I could run Gentoo on the Raspberry Pi, put Gentoo amd64 into /mnt/gentoo, fix CLAGS in make.conf and run something like this:
ROOT=”/mnt/gentoo” emerge -e @world

NeddySeagoon · Posted: Mon Oct 03, 2022 2:36 pm Post subject:

lekto,

Like this.

Before you build anything copy over bits of /etc/portage and copy over the world file.
The Pi 4 is quite capable of building for itself but cross distcc can move the heavy lifting to a build farm. The helper arches don't matter.

The mainline kernel is supposed to mostly work on the Pi4 but I've not tried it yet.

When you get to using emerge to update things run

pingtoo · Posted: Mon Oct 03, 2022 4:02 pm Post subject:

I am curious what Gentoo-amd64 binary provide that Gentoo-arm64 cannot do?

I would imagine copy NAS data portion to pi4 with same path and copy your NAS function's configurations to pi4 that will close enough to begin.

lekto · Posted: Mon Oct 03, 2022 4:07 pm Post subject:

tI know how to install Gentoo on Raspberry Pi 4, I did it once using Debian live and chroot like in amd64, I even installed UEFI so I can use grub. This question was about how to do specifically this, I don't want to do this*, but I'm curious how to do this.
I'm talking about changing arch in fully working and configured system so I don't have to configure everything (except kernel and bootloader) from scratch.

PS. I think that method from my post would messed up permissions, if system was installed before acct-group and acct-user.

* I tried 3 different USB to SATA adapters for 2.5" SSDs and all of them after a while started throwing errors about current on USB and system froze. I even modded my RP to allow USB to draw more current, but same result. I could power SSDs from separate PSU and add separate 12V PSU for 3.5" HDD, but this would make it over complicated and more error prone and I don't like to risking my data.

pingtoo · Posted: Mon Oct 03, 2022 4:25 pm Post subject:

I suppose it is possible, (I didn't do it myself) you have build a RPI4 like Neddy suggested first. Once you have a it build and working then add QEMU package to your RPI4. Then you can do as your first post copy everything amd64 to /mnt/gentoo (exclude kernel/initrd) then copy your QEMU's x86_64 user binary in to /mnt/gentoo/usr/bin/ that might do what you asking. Please see more detail in Gentoo/Qemu

NeddySeagoon · Posted: Mon Oct 03, 2022 4:33 pm Post subject:

lekto,

You could cross compile almost eveything.
The target root would be in

logrusx · Veteran Joined: 22 Feb 2018 Posts: 1532

While you can salvage a lot of your configuration, you can't salvage any of your binaries. In essence this is going to be a new installation. If you're familiar with the process of installation and portage, you're going to be able to figure out almost everything on the go. For example you can grab your existing world file and edit out some arch dependent packages right away. Having both systems side by side is going to be a huge convenience for you. Expect it to take more time than you think it will, should you decide to attempt it.

Regards,
Georgi

NeddySeagoon · Posted: Mon Oct 03, 2022 5:53 pm Post subject:

logrusx,

Portage should catch the arch dependent binaries as they won't be keyworded.
Some -bins will be fine as they support multiple arches.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

logrusx · Veteran Joined: 22 Feb 2018 Posts: 1532