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From: "Ludovic Courtès" <ludo@gnu.org>
To: Vagrant Cascadian <vagrant@debian.org>
Cc: 36117@debbugs.gnu.org
Subject: bug#36117: qemu-binfmt with non-native chroot
Date: Fri, 07 Jun 2019 15:00:32 +0200	[thread overview]
Message-ID: <87blz9ft3j.fsf@gnu.org> (raw)
In-Reply-To: <87r286zjhu.fsf@yucca> (Vagrant Cascadian's message of "Thu, 06 Jun 2019 10:55:25 -0700")

Hi!

Vagrant Cascadian <vagrant@debian.org> skribis:

> On Guix there are no flags set, and the binary used is a dynamically
> linked executable:
>
>   $ cat /proc/sys/fs/binfmt_misc/qemu-aarch64
>   enabled
>   interpreter
>   /gnu/store/sw2rrqmjij73wcy3ajd47ypvmzh12yz6-qemu-3.1.0/bin/qemu-aarch64
>   flags:
>   offset 0
>   magic 7f454c460201010000000000000000000200b700
>   mask ffffffffffffff00fffffffffffffffffeffffff
>
>
> So there are (at least) two things needed to make this work on Guix:
>
> * A way to set the flags on qemu-binfmt-service-type.
>
> * A static build of qemu-user targets
>
> * A way to set which qemu to use for qemu-binfmt-service-type.
>
> The *three* things are...
>
>
> With this working correctly foreign-architecture chroots would become
> trivial:
>
>   # on an amd64 host:
>   $ debootstrap --arch=arm64 buster buster-chroot http://deb.debian.org/debian
>   ...
>   $ chroot buster-chroot /bin/bash
>
>
> Enabling qemu-binfmt-service-type to operate in this way would obviate
> the need for the "guix-support?" qemu-binfmt-configuration option, as
> you could simply assemble the build environment without having to
> include all of qemu's dependencies in the container.
>
> It's a pretty magical feature.

True!  Though adding all the dependencies of QEMU in the chroot the way
‘guix-support?’ does it turns out to be pretty magical too ;-), because
we can precisely list those dependencies and include nothing but these
dependencies in the chroot—something that cannot be done on an FHS
system.

As an quick workaround, perhaps you could bind-mount all the entries of:

  guix gc -R $(guix build qemu)

in your Debian chroot?

(Speaking of which… it would be great to have a Debian API in Guix, where
you could write, say:

  (debian-build #~(system (string-append "/bin/uname > "
                                         #$output)))

Food for thought…)

Thanks,
Ludo’.

  reply	other threads:[~2019-06-07 13:01 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-06 17:55 bug#36117: qemu-binfmt with non-native chroot Vagrant Cascadian
2019-06-07 13:00 ` Ludovic Courtès [this message]
2019-06-08  6:03   ` Vagrant Cascadian
2019-06-24 12:25     ` Ludovic Courtès
2021-02-22 19:50       ` bug#36117: [PATCH 1/4] gnu: qemu: Fix indentation and remove trailing #t Maxim Cournoyer
2021-02-22 19:50         ` bug#36117: [PATCH 2/4] gnu: Add glib-static Maxim Cournoyer
2021-02-22 19:50         ` bug#36117: [PATCH 3/4] gnu: qemu: Add a static output Maxim Cournoyer
2021-02-23  8:38           ` Ludovic Courtès
2021-02-25 13:57             ` Maxim Cournoyer
2021-02-25 14:50               ` Ludovic Courtès
2021-02-22 19:50         ` bug#36117: [PATCH 4/4] services/qemu-binfmt: Use the F flag and the static output of QEMU Maxim Cournoyer
2021-02-23  8:37           ` Ludovic Courtès
2021-02-25 21:47             ` Maxim Cournoyer
2021-03-15 22:07               ` bug#36117: qemu-binfmt with non-native chroot Maxim Cournoyer

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