[gentoo-alt] 'Continuous Integration' for Gentoo Prefix?

[Sam Pfeiffer]

Hello,

First, let me apologise if I have any wrong preexisting ideas/guesses about
Gentoo Prefix and how it is developed. Secondly, sorry if this email is a
bit too long.

I'll present myself, explain my use-case and my troubles and tricks, and
then ask for feedback.

Hello, I'm Sammy Pfeiffer. I am a PhD student at University of Technology
Sydney. I'm a (software) robotics engineer pursuing my PhD in a lab with a
bunch of different robots and machine learning setups. I'm using Gentoo
Prefix for deploying a big bunch of software into robots where the OS is
old and frozen (and also to deploy in computation farms experiments... once
again with no option to touch the OS). (The bunch of software is ROS, the
'Robotics Operating System' which has a ton of dependencies, and there is
an existing overlay which I'm helping on maintaining and improving (
https://github.com/ros/ros-overlay)).

I'd like to share the trick I found to overcome a few annoying bits of my
platforms:
* I have no root access in the machines I need to deploy.
* The machines don't have Docker installed (too old kernel anyways).
* I have 32 bit and 64 bit machines (the OS running in them is).
* I have a different username (and home folder) on each machine.
* Each machine has a different disk(s)/partition(s) structure (main issue
here is that I may need to use a different disk to store my data, cause of
size constrains).

The trick to be able to use Gentoo Prefix with all these constraints
bootstrapping it only once is to set the EPREFIX to /tmp/gentoo.
Then you can deploy the full bootstrapped system in any folder/disk and
just do a softlink to /tmp/gentoo. This works nicely (I was scared of the
softlink breaking stuff somewhere, but it was alright).
The other trick is to bootstrap a 32bit Gentoo Prefix, which can be run in
any 32b or 64b box (it's not ideal but simplifies my deployment currently).

Also, having all these machines use the same Gentoo Prefix in the same
place, with the same 32bit compilation, I can setup a binary package
server, which all the deployments can point to and just get all the
packages skipping the long compilation times (specially in very old and low
powered machines).

The final trick I'm experimenting with is to use a set of Docker images
(and soon in a continuous integration environment) to bootstrap all the
system. With that I can save snapshot of successfully built systems &
packages to serve as an easy deployment (and easy installation of extra
packages thru the binary package server).

Given my particular annoyance of the 32bit system (and noting that my hosts
are 64bits, as is the standard nowadays) I found that I can use either:
* https://github.com/docker-32bit/ubuntu a 32bit Ubuntu Docker image
* https://github.com/gentoo/gentoo-docker-images stage3-x86 32bit Gentoo
Docker image

And then execute the build step of Docker with:

setarch i686 docker build -t my_bootstrapping_gentoo_prefix_32b_image .

Which will trick any program trying to do uname -m to assume 32bit machine.
(Previously I used the variable CHOST=i686-pc-linux-gnu for bootstrapping,
but I found some problems, which didn't appear with this method).

Once I have all this setup working nicely, I'd like to trigger rebuilds
every X time, and on changes on main players (or all dependencies actually)
of my setup, like the bootstrapping of Gentoo Prefix (Ideally, on every
change of a part of the system just trigger a rebuild from that point on,
Docker layers make this possible).

With Azure announcing unlimited minutes on CI/CD for open source projects:
https://azure.microsoft.com/en-us/blog/announcing-azure-pipelines-with-unlimited-ci-cd-minutes-for-open-source/

Even bootstrapping Gentoo prefix, with pieces of software like gcc taking
very long to compile, is possible.

The point is: I have been trying to build Gentoo Prefix during the last
days after a few months of break since the last time I touched the system.
And it's failing. I haven't managed yet to bootstrap it completely. I feel
there is no CI/CD setup to catch these issues and be able to offer a
working version of Gentoo Prefix at any time.

I was going to build it for myself (cause I need it), but instead, I'd like
to offer my help to build it for the community. At least offer as an option
ready-to-use /tmp/gentoo EPREFIX'ed built Gentoo Prefix from a Docker
image, just copy the full folder structure, do the softlink, and you are
ready to play with Gentoo. If you mess up anything, just re-deploy.

To do this I'd need a bit of help as I'm quite new to Gentoo and I tend to
get blocked on little issues that take a while to google or debug
(specially with the long compilation times of the bootstrap and some big
packages).

I've posted a short issue in the Docker repo of Gentoo images about this (
https://github.com/gentoo/gentoo-docker-images/issues/62) but I think the
maintainers probably don't usually work with Gentoo Prefix.

Thank you very much for your time, and for your open source efforts.

-- 

*Sammy Pfeiffer*
PhD Candidate at The Magic Lab within UTS.