Re: Qemu binfmt on foreign distro

[Ludovic Courtès]

Hi,

Mathieu Othacehe <address@hidden> skribis:

> I ran further tests. On Ubuntu 18.04, using qemu-user-static or
> qemu-user-binfmt makes no difference, they both fail.
>
> qemu-user-static works on Ubuntu 19.04 because of the addition of the
> 'F' flag, see:
> https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1815100.
>
> Adding the 'F' flag[1] manually on Ubuntu 18.04 also fixes the issue.

Right, so there are two things you need for emulated builds to work: (1)
the qemu-xyz program must be visible in the container, and (2) the
dynamic linker and shared libraries it refers to must also be visible.

The ‘F’ flag solves #1, and using a statically-linked QEMU solves #2.

> I could maybe add an entry to the documentation explaining that, in
> order for '--system' command to work on foreign distros, it is needed
> that:
>
> * A static version of qemu-user is used by binfmt
> * The 'F' flag is enabled for all binfmt installed entries

That has to be worded carefully: it’s only for foreign distros, and only
for architectures that the CPU doesn’t support (x86_64 can do i686, and
some AArch64 CPUs can do ARMv7).

Perhaps it could be a sub-section under “Application Setup”, linked from
the ‘--system’ documentation?

Thanks,
Ludo’.