Learn NetBSD - Embedded, ARM & Portability Deep-Dive

#Introduction

In episode 19 we optimized NetBSD's performance. Now we return to the root of its identity: portability. In this episode we'll dive into embedded, ARM, and a portability deep-dive — exploring architecture support like arm64, riscv, and evbarm, building systems cross-arch for embedded devices, and real-world application on SBCs, routers, and legacy hardware revival.

This is the episode that answers the question "why NetBSD?" — because not many operating systems can run smoothly on a Raspberry Pi, on a small router, and on old server hardware, all from the same source tree. Let's dissect how this portability magic works.

#The Architecture Port Map

NetBSD's strength lies in its broad architecture support. Each architecture has a "port" — a directory in the source tree containing CPU, platform, and device support. See for yourself:

ls /usr/src/sys/arch

amd64  arm  arm64  evbarm  evbmips  m68k  mips  powerpc  riscv  sparc64  vax  ...

evbarm and evbmips are examples of NetBSD's port design: one port for "various boards", where each board is configured via kernel configs and device trees.

#Building for Another Architecture

You don't need to own a device to build its system — that's the power of cross-building from episode 10. Let's build a kernel for the Raspberry Pi (aarch64/evbarm) from an x86 machine:

#1. Get the Source

cd /usr/src
./build.sh -m evbarm-aarch64 tools

Building tool: nbtoolchain-gcc-...

tools builds the toolchain for the target architecture — here evbarm-aarch64.

#2. Build the Kernel

./build.sh -m evbarm-aarch64 kernel=GENERIC64

...
copying netbsd to .../evbarm-aarch64/obj/release/kernels/GENERIC64/netbsd

#3. Build the World

./build.sh -m evbarm-aarch64 -u distribution

#   build.sh: Building the distribution
...
#   Creating release sets

One source set, many targets. This is the flow projects use to provide images for hundreds of devices from a handful of build servers.

#SBCs: Raspberry Pi and Pine64

#Raspberry Pi

NetBSD supports the Raspberry Pi from the early generations up to the Pi 4 and Pi 5 via the evbarm port. Once the kernel and world are ready, the SD image is prepared with a FAT partition for the firmware plus an FFS partition for root:

# FAT (boot) + FFS (root) partitions, then copy files:
cp -r evbarm/obj/distrib/evbarm/raw/ . 
# follow the instructions to copy to the /mnt boot and root partitions

Booting a Pi with NetBSD gives you a full UNIX system on a device drawing less than 5 watts — ideal for a small personal server, DNS, or gateway managed with sysctl hw.model.

#Pine64

The Pine64 — a family of 64-bit ARM boards — is also well supported by NetBSD. For devices with more RAM and storage, the Pine64 is often chosen to run home servers: use pkgsrc to install nginx, and you have an ARM web server.

#Routers and Gateways

One of NetBSD's most popular embedded use cases is the router/gateway — because everything you need is already in the base system: npf (firewall + NAT), routing, IPv6, and bridging. The concepts from episodes 8, 12, and 16 come together:

ifconfig_wm0="inet 192.168.1.1 netmask 255.255.255.0"
ifconfig_re0="inet 203.0.113.5 netmask 255.255.255.0"
defaultroute="203.0.113.1"

sysctl -w net.inet.ip.forwarding=1
npfctl start

net.inet.ip.forwarding=1

With this combination, a small board (or an old PC) becomes a full NAT router with a firewall — lightweight, stable, and securely manageable over SSH.

#Legacy Hardware Revival

NetBSD's portability also means bringing old hardware back to life. Sun workstations with sparc64, old PowerPC Macs, even VAX machines — NetBSD makes them useful again. The value is twofold:

• Cost savings: full-powered servers without buying new hardware.
• Preservation: historical devices stay alive and in use.
• Learning: understanding different architectures is a remarkable mental exercise.

sysctl hw.machine
sysctl hw.model

hw.machine = sparc64
hw.model = SUNW,UltraSPARC-IIi (1000MHz)

#Choosing the Right Device

#Closing

In this episode 20, you've dived into the soul of NetBSD: the architecture port map like arm64, riscv, and evbarm, the cross-build flow for embedded devices, and real-world use on SBCs (Raspberry Pi, Pine64), routers/gateways, and legacy hardware revival.

Key takeaways:

• NetBSD ports cover amd64, arm64, evbarm, riscv, evbmips, sparc64, vax, and many more.
• Cross-build with ./build.sh -m <platform-arch> builds a kernel/world without the physical device.
• evbarm is the port for many ARM boards at once.
• Router/gateway is the most practical case: npf + routing + IPv6 from the base system.
• NetBSD revives old hardware — savings and preservation in one.

In the next episode, episode 21, we'll look at the current state of things: NetBSD 11.0 and the roadmap — the latest release features, the modern toolchain, RISC-V/ARM improvements, and the branch support lifecycle. See you in episode 21!