On Thu, Jun 22, 2023 at 10:10:06AM +1000, Ralph Ronnquist wrote:
> On Wed, Jun 21, 2023 at 08:32:00PM +0100, Adam Sampson via Dng wrote:
> > Didier Kryn <kryn@???> writes:
> >
> > >> # chroot /mnt /bin/bash
> > >
> > > Maybe I'm going crazy but this is absolutely impossible. You must not
> > > only enter the new filesystem, you must also change the cpu. You need
> > > qemu for this, certainly not a bare chroot.
> >
> > It's not impossible, but it does require some setup first. There's a
> > userspace-only version of qemu that translates target-machine system
> > calls into native system calls, and you can set up Linux's support for
> > custom binary formats so qemu-user gets invoked automatically when you
> > try to run a non-native executable. The emulation's not as good as
> > qemu's full-machine emulation (in particular, it tends to have limited
> > support for recently-added system calls), but it usually works well
> > enough for bootstrapping.
> >
> > The Debian wiki has some notes on how to set it up:
> > https://wiki.debian.org/QemuUserEmulation
>
> Using plain multiarch setup did indeed come into play fairly recently;
> might have been 2017 or so when I "discovered" it. Before that one
> needed a complete filesystem with a qemu-static setup, or, as Didier
> suggests, a separate VM already in the target architecture.
>
> We, toddlers of today, use multiarch; it's two simple commands:
>
> # dpkg --add-architecture armhf
> # apt-get update
Sorry; it of course needs a third command, to install libraries in
armhf as well:
# apt-get upgrade
Ralph.
>
> and then the (amd64) system is all setup to run armhf binaries via the
> automatic emulation (using binfmt I believe). You do not need an armhf
> kernel to run armhf binaries.
>
> Obviously those binaries are executed with respect to the host machine
> hardware which very likely is different from the target machine
> hardware. But it's generally good enough for both spinning up a target
> filesystem, and for building a kernel for a target filesystem. (The
> latter is partly made possible with how target hardware nowadays is
> separated out with DTB declarations, which provide hardeware ABI
> descriptions for kernel software).
>
> Thus, following those two commands, you may spin up a target
> filesystem, e.g., the way I did it:
>
> # debootstrap --variant=minbase --no-merge-usr --arch armhf \
> chimaera /mnt http://deb.devuan.org
>
> That was they way I set up the two armhf build hosts I'm providing for
> devuan package building.
>
> Some hardware modules I got from a near-miss Armbian version; this was
> a year ago but afair my hosts are 805 cpus that needed something
> special for networking.
>
> You might have similar success with getting a working Armbian
> boot+filesystem for your hardware and then just replace the filesystem
> with a Devuan debootstrapped filesystem. It's easier if you don't need
> to compile the kernel yourself.
>
> Ralph.
>
> >
> > --
> > Adam Sampson <ats@???> <http://offog.org/>
> > _______________________________________________
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Re: [DNG] [rrq@mail.rrq.id.au: Re: …
