Pi:dev build environment

Working draft. Procedure re-validated 2026-05-05 on Pi OS Bookworm / Pi 5.

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Reproducible procedure for setting up a build host that produces stretch-armhf binaries (compatible with the Raspbian-9 base used by NextPi) on any modern aarch64 Raspberry Pi running Pi OS Bookworm.

Why

NextPi releases ship as Raspbian 9 (stretch) armhf binaries. This procedure builds those binaries inside a stretch-armhf chroot hosted on a modern aarch64 Pi. aarch64 hardware can execute armhf userspace natively via aarch32 compat, so the build runs at host CPU speed without QEMU emulation, while the toolchain and libraries remain pinned to stretch for ABI compatibility with the deployment target. Apt sources point at the project's stretch mirror at http://zx.xalior.com/nextpi_dev, which keeps package versions deterministic across build hosts.

Measured speedup, libspectrum 1.6.0 build:

Build host	Time	Ratio
Pi 3, 4× Cortex-A53 armv7l, SD card (native stretch)	65 s	1.0×
Pi 5, 4× Cortex-A76 aarch64, NVMe (chroot)	11 s	5.9×

Prerequisites

• Vanilla Pi OS Bookworm on a Pi 4 or Pi 5 with ~5 GB free disk.
• SSH access as a sudo-capable user.
• Network reach to zx.xalior.com.

Procedure

1. Install host tooling

sudo apt-get update
sudo apt-get install -y debootstrap qemu-user-static binfmt-support

Verify:

dpkg --print-foreign-architectures   # should list: armhf
ls /proc/sys/fs/binfmt_misc/ | grep qemu-arm

2. Add the apt signing key

curl -sL https://zx.xalior.com/nextpi_dev/debian_nextpi.key \
  | sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/debian_nextpi.gpg

Confirm:

sudo gpg --no-default-keyring --keyring /etc/apt/trusted.gpg.d/debian_nextpi.gpg --list-keys
# pub rsa2048 2012-04-01 [SC] A0DA38D0D76E8B5D638872819165938D90FDDD2E
# uid Mike Thompson (Raspberry Pi Debian armhf ARMv6+VFP)

3. Debootstrap the chroot

sudo debootstrap --arch=armhf --variant=buildd \
    --keyring=/etc/apt/trusted.gpg.d/debian_nextpi.gpg \
    stretch /srv/nextpi-buildroot/ \
    http://zx.xalior.com/nextpi_dev

Ends with W: Failure while configuring required packages. Continue.

4. Neutralise segfaulting postinsts and force-install

for pkg in systemd plymouth mountall; do
  printf '#!/bin/sh\nexit 0\n' \
    | sudo tee /srv/nextpi-buildroot/var/lib/dpkg/info/${pkg}.postinst > /dev/null
  sudo chmod +x /srv/nextpi-buildroot/var/lib/dpkg/info/${pkg}.postinst
done

sudo chroot /srv/nextpi-buildroot \
    /usr/bin/env -i PATH=/usr/sbin:/usr/bin:/sbin:/bin LANG=C \
    /bin/bash -c "dpkg --install --force-depends --force-confdef --force-confold --force-overwrite --force-bad-version --recursive /var/cache/apt/archives/"

Errors on systemd, plymouth, mountall are expected. Verify:

sudo chroot /srv/nextpi-buildroot \
    /usr/bin/env -i PATH=/usr/sbin:/usr/bin:/sbin:/bin LANG=C \
    /bin/bash -c "type apt-get && type gcc"

5. Bind-mount runtime filesystems

for m in proc sys dev dev/pts; do
  sudo mkdir -p /srv/nextpi-buildroot/$m
  sudo mount --bind /$m /srv/nextpi-buildroot/$m
done
sudo cp /etc/resolv.conf /srv/nextpi-buildroot/etc/

Session-only; see Persistent mounts for fstab.

6. Hold systemd, plymouth, mountall

sudo chroot /srv/nextpi-buildroot \
    /usr/bin/env -i PATH=/usr/sbin:/usr/bin:/sbin:/bin LANG=C \
    /bin/bash -c "apt-mark hold systemd plymouth mountall"

7. Install the NextPi 1.92D package set + dev variants

sudo chroot /srv/nextpi-buildroot \
    /usr/bin/env -i PATH=/usr/sbin:/usr/bin:/sbin:/bin LANG=C HOME=/root \
    /bin/bash -c "
        apt-get update -qq && \
        wget -q -O /tmp/buildroot.packages https://zx.xalior.com/nextpi_dev/buildroot.packages && \
        DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
            \$(cat /tmp/buildroot.packages)
    "

~50 s on Pi 5 / NVMe; chroot grows to ~2.0 GB. Toolchain check:

sudo chroot /srv/nextpi-buildroot /usr/bin/env -i PATH=/usr/sbin:/usr/bin:/sbin:/bin /bin/bash -c \
    "gcc --version | head -1; automake --version | head -1; libtool --version | head -1; pkg-config --version"

Expect: gcc 6.3.0, automake 1.15, libtool 2.4.6, pkg-config 0.29.

8. Smoke test: build libspectrum 1.6.0

sudo chroot /srv/nextpi-buildroot \
    /usr/bin/env -i PATH=/usr/sbin:/usr/bin:/sbin:/bin LANG=C HOME=/root \
    /bin/bash -c '
        cd /tmp && \
        wget -q https://sourceforge.net/projects/fuse-emulator/files/libspectrum/1.6.0/libspectrum-1.6.0.tar.gz/download -O libspectrum-1.6.0.tar.gz && \
        tar xzf libspectrum-1.6.0.tar.gz && \
        cd libspectrum-1.6.0 && \
        ./configure --with-fake-glib --quiet && \
        time make -s
    '

~10–15 s on Pi 5 / NVMe. Verify:

file /srv/nextpi-buildroot/tmp/libspectrum-1.6.0/.libs/libspectrum.so.8.10.0
# ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked

Persistent mounts

Add to /etc/fstab:

/proc        /srv/nextpi-buildroot/proc      none  bind  0 0
/sys         /srv/nextpi-buildroot/sys       none  bind  0 0
/dev         /srv/nextpi-buildroot/dev       none  bind  0 0
/dev/pts     /srv/nextpi-buildroot/dev/pts   none  bind  0 0

/etc/resolv.conf needs re-copying after host reboot.

Sources

• Apt mirror: http://zx.xalior.com/nextpi_dev stretch main contrib non-free rpi firmware.
• Signing key: https://zx.xalior.com/nextpi_dev/debian_nextpi.key — sha256 ca59cd4f2bcbc3a1d41ba6815a02a8dc5c175467a59bd87edeac458f4a5345de. Byte-identical to https://archive.raspbian.org/raspbian.public.key.
• Package list: https://zx.xalior.com/nextpi_dev/buildroot.packages — 369 entries (NextPi 1.92D installed set, less firmware/kernel/Pi-hardware, plus available -dev variants).
• Smoke-test source: libspectrum 1.6.0 from https://sourceforge.net/projects/fuse-emulator/files/libspectrum/.