New blog post! Installing freebsd-armv7.

content/posts/freebsd-arm-qemu/index.md

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+---
+title: "Emulating *BSD on ARM, Part 2: FreeBSD"
+date: 2024-11-11T20:52:35+01:00
+---
+
+In [Part 1](/posts/bsd-arm-qemu/) of this blog post series, I explained how I recently spent some time getting various BSD OSes to run on QEMU, for 32-bit ARM (ARMv7). This part deals with FreeBSD.
+
+*Spoiler: it was easier than the others.*
+
+I started by downloading an image from
+https://download.freebsd.org/releases/arm/armv7/ISO-IMAGES/. Mine was
+called
+[FreeBSD-14.1-RELEASE-arm-armv7-GENERICSD.img.xz](https://download.freebsd.org/releases/arm/armv7/ISO-IMAGES/14.1/FreeBSD-14.1-RELEASE-arm-armv7-GENERICSD.img.xz).
+
+## Preparing UEFI {#uefi}
+
+Warner Losh has thankfully written [a blog
+post](http://bsdimp.blogspot.com/2023/12/freebsdarmv7-in-qemu.html)
+about how to get it running in QEMU, which we are going to follow.
+
+In the post, he explains that QEMU contains a version of Tianocore EDK2 for 32-bit ARM. If you don't know about Tianocore, it is a UEFI firmware -- similar to the BIOS of a PC, except it's not built in. It abstracts away the low-level hardware bits and presents a standardized interface to the user and the bootloader.
+
+So let's create two virtual flash devices -- one read-only containing EDK2, one r/w for any UEFI variables that should be saved. The read-only one can be shared across VMs, for the other one you should have a copy per VM.
+
+```shell
+#!bin/sh
+
+dd if=/dev/zero of=pflash0.img bs=1m count=64
+dd if=/dev/zero of=pflash1.img bs=1m count=64
+dd if=/opt/pkg/share/qemu/edk2-arm-code.fd of=pflash0.img conv=notrunc
+dd if=/opt/pkg/share/qemu/edk2-arm-vars.fd of=pflash1.img conv=notrunc
+```
+
+Here, QEMU is installed through [pkgsrc](https://pkgsrc.org/) in `/opt/pkg`. If your installation is in a different directory, you may have to adjust the paths.
+
+## Creating the QEMU startup script
+
+QEMU is fully configured through command-line options. Thus, the command lines are long and difficult to get just right. QEMU command lines are typically passed on from user to user, like a cargo cult. Here is mine for FreeBSD-ARM:
+
+```shell
+#!/bin/sh
+
+qemu-system-arm \
+	-M virt \
+	-m 4096 \
+	-drive file=pflash0.img,format=raw,if=pflash,readonly=on \
+	-drive file=pflash1.img,format=raw,if=pflash \
+	-drive file=FreeBSD-14.1-RELEASE-arm-armv7-GENERICSD.img,format=raw,if=virtio,cache=writethrough \
+	-device virtio-net,netdev=net0,mac="52:54:00:12:34:55" \
+	-netdev type=user,id=net0 \
+	-device virtio-gpu-pci \
+	-usb -device nec-usb-xhci \
+	-device usb-kbd -device usb-mouse \
+	-nographic
+```
+
+## EFI wrangling
+
+Upon launch, we get a UEFI shell prompt:
+
+{{< figure src="uefi-shell.png" title="Welcome to the UEFI shell! Remember DOS?" width=561 >}}
+
+The EFI shell
+([here is a primer](https://www.intel.com/content/dam/support/us/en/documents/motherboards/server/sb/efi_instructions.pdf) from Intel)
+is strangely reminiscent of a DOS prompt. First, set the current device by typing
+
+```
+fs0:
+```
+
+You can now explore the contents with `dir` and change directories with `cd`. To boot, run this command:
+
+```
+EFI\boot\bootarm
+```
+
+To get this setting to stick in future reboots, create a `startup.nsh` file -- the EFI equivalent to `autoexec.bat` -- on the running system, as root:
+
+```shell
+echo 'fs0:\efi\boot\bootarm' > /boot/efi/startup.nsh
+```
+
+## That's it!
+
+The FreeBSD/arm system from the image is immediately ready for action! No installation is needed. I was able to install some binary packages for armv7 simply by running
+
+```shell
+pkg update
+pkg install python311 go123
+```
+
+All in all, this FreeBSD experience was about as frictionless as it gets, once you have cleared the hurdle of getting QEMU to run with the right settings.
+
+You can quit the emulator and go back to the host shell by running `halt -p` as root.
+
+In the next installment, we are going to install OpenBSD/armv7.