No support for mixed architectures (32-bit on 64-bit)

[mcassaniti]

mkosi commit the issue has been seen with

main

Used host distribution

Ubuntu 24.04 (noble)

Used target distribution

Ubuntu 24.04 (noble)

Linux kernel version used

6.8.0-31-generic

CPU architectures issue was seen on

x86_64

Unexpected behaviour you saw

I added the file apt-extra/var/lib/dpkg/arch with the contents below. This is the equivalent of running dpkg --add-architecture i386 on an amd64 machine. I could not install any i386 based packages.

amd64
i386

Used mkosi config

# Only relevant content shown

[Distribution]
PackageManagerTrees = apt-extra

[Content]
Packages = libc6:i386

mkosi output

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package libc6:i386
‣ "apt-get -o APT::Architecture=amd64 -o APT::Architectures=amd64 -o APT::Install-Recommends=false -o APT::Immediate-Configure=off -o APT::Get::Assume-Yes=true -o APT::Get::AutomaticRemove=true -o APT::Get::Allow-Change-Held-Packages=true -o APT::Get::Allow-Remove-Essential=true -o APT::Sandbox::User=root -o Acquire::AllowReleaseInfoChange=true -o Dir::Cache=/var/cache/apt -o Dir::State=/var/lib/apt -o Dir::Log=/var/log/apt -o Dir::State::Status=/buildroot/var/lib/dpkg/status -o Dir::Bin::DPkg=/usr/bin/dpkg -o Debug::NoLocking=true -o DPkg::Options::=--root=/buildroot -o DPkg::Options::=--force-unsafe-io -o DPkg::Options::=--force-architecture -o DPkg::Options::=--force-depends -o DPkg::Options::=--no-debsig -o DPkg::Use-Pty=false -o DPkg::Install::Recursive::Minimum=1000 -o pkgCacheGen::ForceEssential=, install libc6:i386" returned non-zero exit code 100.

[mcassaniti]

The underlying issue is setting -o APT::Architectures=amd64 which overrides the additional file. Is this a case that the project wishes to support?

[behrmann]

That's an edge case. I think only Debian does multilib the way Debian does it.

I don't think we want to set up sources.list for multiple architectures—users needing that can use package manager trees or skeletons. If dropping the -o APT::Architectures= line is enough to fix it or if changing it to only defaulting to debarch and reading the arches from /var/lib/dpkg/arch in the package manager tree or root is enough to fix it and this doesn't interfere with the single arch case, than I think changing that would be fine.

[mcassaniti]

Dropping the option is sufficient with the basic testing I've done but let me do a more thorough test and get back to you.

[DaanDeMeyer]

systemd has a concept of secondary architectures so that i386 is a secondary architecture for x86-64. We could add that as well by adding a secondary() method to he Architecture enum which returns the secondary architecture if there is one and then set APT::Architectures to both the main and secondary architectures.

[behrmann]

I'm not sure we should do this in all cases. I'm not entirely sure how to understand the man page there

The initial default is always the system's native architecture (APT::Architecture), and foreign architectures are added to the default list when they are registered via dpkg --add-architecture.

i.e. whether setting this is equivalent to having done the dpkg --add-architecture. I for one am quite happy to finally getting rid of having multilib systems, so if this would were equivalent to running to dpkg --add-architecture, I'd rather have this be opt in.

[mcassaniti]

After poking and prodding I've given up and opted to use a post-install script. This one really should be marked as wont-fix unless you want to test all the bits.