create-openbsd-dev-env

Create an OpenBSD dev/test VM for ponyc

Stand up a local OpenBSD VM that matches the ponyc tier-3 CI job, so you can build and test ponyc on OpenBSD without GitHub Actions.

OpenBSD's tier-3 job exercises paths the Linux jobs never do: the static-PIE --static embedded-LLD link recipe, OpenBSD's base clang/libc++, and the per-process datasize limit that the LLVM build pushes against. It also asserts the use= build options that can't work there are rejected. So this VM is the authoritative local environment for OpenBSD-platform ponyc issues. (It is clang-based — OpenBSD's base compiler is clang, not gcc. For gcc-specific issues use the DragonFly skill instead.)

Run the repo-relative commands (rsync of the source) from your ponyc checkout root. The VM itself lives in a separate directory ($VMDIR).

Each fenced sh block below is self-contained. It re-sets VMDIR/OPENBSD_VERSION (and, where needed, the SSH command) at its top, because an agent runs each block as a fresh shell — environment variables and the working directory do NOT carry from one block to the next. Do not "optimize" by setting them once and dropping them from later blocks: an empty $SSH would make a $SSH /bin/sh <<'EOF' ... EOF heredoc run on your host (silently) instead of in the VM — and Step 5 contains newfs and Step 6 edits /etc/login.conf. Keep every block whole. Pick your VMDIR/OPENBSD_VERSION once and use the same values in every block.

Gotchas that will bite you (read first)

OpenBSD is a hybrid of the other two BSD skills: like FreeBSD it boots from a cloud-init seed and is driven entirely over ssh (no VGA-console automation), but like DragonFly the build lives on a dedicated data disk. These matter:

• Per-block fresh shells. See above: re-establish VMDIR/OPENBSD_VERSION/SSH in every block; never let $SSH be empty in front of a /bin/sh heredoc.
• You log in as openbsd, not root. The cloud-init seed creates the openbsd user in the wheel group and writes /etc/doas.conf (permit nopass keepenv :wheel). Build and test run as openbsd; the few root operations (disk setup, package install, editing login.conf) go through doas, which is configured before first login and persists on disk. There is no expect/su bootstrap — OpenBSD's cloud-init runs write_files, so doas is in place from the first boot (simpler than FreeBSD).
• doas is in the base system. Nothing to install; cloud-init just drops /etc/doas.conf. Keep its 0600 root:wheel permissions exactly — doas refuses to run with a group- or world-writable config.
• Cloud-init means no console driving. Unlike the DragonFly skill there is no QEMU sendkey/screendump/monitor dance — just boot and wait for ssh. But the first boot runs cloud-init (user + key + doas.conf), so ssh is not instant; poll for it (Step 4).
• Build on the /build data disk, not /home. OpenBSD's default disklabel confines writable space to /home (~10.8G), which the LLVM 22 build overflows. A second qcow2 is partitioned, newfs'd, and mounted at /build, and the source plus the build live there — mirroring the DragonFly job. The disklabel setup is one-time and not idempotent (newfs reformats), so run Step 5 exactly once.
• The /build mount is not persisted across reboot. disklabel/newfs/mount are manual one-time steps with no /etc/fstab entry; after a guest reboot, remount /dev/sd1a at /build. /etc/login.conf and /etc/doas.conf are on the root disk and do persist.
• Raise the datasize limit. OpenBSD caps a process's data segment in /etc/login.conf (1536M on the stock 7.9 image); the LLVM build needs more, so Step 6 raises datasize-max/-cur to at least 4096M. Without it the libs build dies with allocation failures partway through. The edit is on the root disk and persists.
• OpenBSD's base system has no bash. /bin/sh is a POSIX ksh; in-VM scripts must be POSIX sh. Don't reach for bashisms in a $SSH /bin/sh heredoc.
• Two pkg_add names look like typos but aren't: python%3 (the %3 selects the 3.x branch) and rsync-- (the trailing -- picks the no-flavor build). Copy them verbatim.
• Detach long in-VM builds. The libs build (LLVM) takes hours; run it nohup … > /build/x.log 2>&1 & and poll the log, so an ssh drop doesn't kill it.

Step 0 — verify prerequisites (do NOT assume they're installed)

This skill needs, on the host:

• an existing ponyc checkout (you run the rsync from it)
• hardware-accelerated virtualization for QEMU (KVM on Linux, HVF on macOS)
• enough free disk for the VM's two sparse qcow2 disks (the shipped root image plus a 50 GB nominal data disk; they grow only as used — the libs build plus a debug build take the data disk to several GB), network access to github.com (the image is a GitHub release asset)
• qemu-system-x86_64 and qemu-img
• genisoimage (builds the cidata seed CD-ROM; cloud-localds can also produce an equivalent cidata image)
• rsync, git, curl
• an OpenSSH client (ssh, scp, ssh-keygen)

Note this is the shortest prerequisite list of the three BSD skills: OpenBSD needs no expect (cloud-init configures doas directly), no xz (the image ships as a plain qcow2 — no decompress, no root-fs resize), and no bsdtar/PPM-converter (it is headless with no ISO header mining and no console screendumps).

Check that every required tool is present. Do not assume the environment has them, and do not install anything yourself — installing them is the user's call (it needs privilege, and the package names vary by OS). If anything is missing, stop, tell the user which tools/capabilities are missing, and ask them to install them with their platform's package manager, then re-run the check before proceeding.

missing=""
for t in qemu-system-x86_64 qemu-img rsync git ssh scp ssh-keygen curl; do
  command -v "$t" >/dev/null 2>&1 || missing="$missing $t"
done
command -v genisoimage >/dev/null 2>&1 || command -v cloud-localds >/dev/null 2>&1 \
  || missing="$missing seed-builder(genisoimage|cloud-localds)"
# Hardware acceleration is host-specific — check the right accelerator for this OS.
case "$(uname -s)" in
  Linux)  [ -w /dev/kvm ] || missing="$missing kvm(/dev/kvm-not-writable)" ;;
  Darwin) qemu-system-x86_64 -accel help 2>&1 | grep -q hvf || missing="$missing hvf-accelerator" ;;
  *)      echo "NOTE: confirm this host has a QEMU hardware accelerator and adjust the boot accel= below" ;;
esac
[ -n "$missing" ] && echo "MISSING:$missing" || echo "all prerequisites present"

If the output is anything but all prerequisites present, name the missing tools/capabilities to the user and ask them to install them however their OS does — do NOT guess a distro package name. (genisoimage ships in genisoimage or cdrkit on Debian/Ubuntu; CI uses genisoimage. If only cloud-localds is available it can build the same cidata image — attach it as the cdrom in Step 3.) A missing hardware accelerator — no writable /dev/kvm on Linux, no HVF on macOS — is a host/BIOS/virtualization fix only the user can make; the VM is unusably slow without it, so don't fall back to TCG emulation.

This flow is verified on Linux+KVM through VM bring-up, the /build disk plus doas/datasize setup, dependency install, the source rsync, and the unsupported-build rejection smoke (.ci-scripts/openbsd-reject-unsupported-builds.sh, which runs cmake … -DPONY_USES=… and so needs no LLVM). The LLVM build (cmake -P lib/build-libs.cmake), the subsequent cmake --preset debug/build — which require the built LLVM (CMake's find_package(LLVM) fails without it) — and the test suites were not run locally; those steps mirror .ci-scripts/bsd/openbsd-provision.bash and the tier-3 openbsd job, which CI exercises end-to-end and keeps green. The guest side is OS-agnostic, so macOS goes through the same steps with the HVF accelerator (accel=kvm:hvf in Step 3 selects it).

Setup

Pick a persistent VM directory and an OpenBSD version that matches ponyc CI (the tier-3 openbsd job in .github/workflows/ponyc-tier3.yml runs OpenBSD 7.9; the exact image URL, including the dated build tag, is in .ci-scripts/bsd/openbsd-provision.bash). Use the same two values in every block below.

1. Download the image + create the build disk (one time)

OpenBSD ships no official cloud image, so CI uses the community hcartiaux/openbsd-cloud-image GitHub release — a plain qcow2 that boots straight to a cloud-init-configured system. Pin the full dated release tag that openbsd-provision.bash references (a bare v7.9 is not a valid asset path). The root image is left at its shipped size; the build does not live on it.

VMDIR=~/vms/openbsd-7.9; OPENBSD_VERSION=7.9
mkdir -p "$VMDIR" && cd "$VMDIR"
curl -fL --retry 3 -o openbsd.qcow2 \
  "https://github.com/hcartiaux/openbsd-cloud-image/releases/download/v7.9_2026-06-03-20-46/openbsd-generic.qcow2"
# Build-workspace disk. OpenBSD's default disklabel confines builds to /home
# (~10.8G), which the LLVM 22 build overflows, so build on a dedicated disk.
qemu-img create -f qcow2 openbsd-data.qcow2 50G

2. Key + cloud-init seed

OpenBSD's cloud-init reads a cidata seed at boot: it creates the openbsd user (in wheel) with your ssh public key, and writes /etc/doas.conf so the openbsd user gets passwordless doas. Build the seed as an ISO and attach it as a CD-ROM (Step 3).

VMDIR=~/vms/openbsd-7.9; cd "$VMDIR"
test -f vm_key || ssh-keygen -t ed25519 -f vm_key -N "" -q
cat > user-data <<USERDATA
#cloud-config
users:
- name: openbsd
  groups: wheel
  ssh_authorized_keys:
  - $(cat vm_key.pub)
write_files:
- path: /etc/doas.conf
  content: |
    permit nopass keepenv :wheel
  owner: root:wheel
  permissions: '0600'
USERDATA
cat > meta-data <<'METADATA'
instance-id: openbsd-dev
local-hostname: openbsd-dev
METADATA
genisoimage -output seed.iso -volid cidata -joliet -rock user-data meta-data

3. Boot (daemonized, persistent)

VMDIR=~/vms/openbsd-7.9; OPENBSD_VERSION=7.9; cd "$VMDIR"
qemu-system-x86_64 \
  -name openbsd-${OPENBSD_VERSION} \
  -machine pc,accel=kvm:hvf -cpu host -smp 8 -m 8G \
  -drive file=openbsd.qcow2,format=qcow2,if=virtio \
  -drive file=openbsd-data.qcow2,format=qcow2,if=virtio \
  -drive file=seed.iso,media=cdrom \
  -netdev user,id=net0,hostfwd=tcp::2222-:22 \
  -device virtio-net-pci,netdev=net0 \
  -display none -pidfile openbsd.pid -daemonize

(accel=kvm:hvf picks KVM on Linux or HVF on macOS and errors if neither is available — it never silently falls back to slow TCG; CI uses bare accel=kvm because it always runs on Linux. -smp/-m are speed knobs; CI uses 4 CPUs / 6G. The build is capped by the 4096M datasize limit per process, not by total RAM. hostfwd 2222->22 is the ssh port — to run two OpenBSD VMs at once, give each its own $VMDIR and a distinct hostfwd port, and pass that port to every ssh/scp/rsync -p. The seed is attached as a cdrom — that is how OpenBSD's cloud-init finds the cidata volume; do not copy FreeBSD's raw-virtio-disk seed form here. This boot command is adapted from .ci-scripts/bsd/openbsd-provision.bash: it adds -pidfile/-smp 8, drops the CI host-bootstrap, and like CI uses no rng or monitor device.)

4. Wait for ssh (first boot runs cloud-init)

VMDIR=~/vms/openbsd-7.9; OPENBSD_VERSION=7.9; cd "$VMDIR"
up=""
for i in $(seq 1 150); do   # ~5 min, matching CI's timeout
  if ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -o ConnectTimeout=2 -i vm_key -p 2222 \
       openbsd@localhost true 2>/dev/null; then up=1; echo "SSH up"; break; fi
  sleep 2
done
[ -n "$up" ] || echo "SSH NEVER CAME UP — see recovery below."

If ssh never comes up, this VM has no VGA console to look at (it booted headless), so diagnose in this order:

• Is the process alive? pgrep -af "qemu-system-x86_64 -name openbsd-${OPENBSD_VERSION}". If it's gone, the boot died early (usually a bad/incomplete image from Step 1) — re-check the Step 1 download and re-boot.
• Watch the boot. The image logs to the serial console, so re-boot with a serial log added — kill "$(cat openbsd.pid)", then re-run the Step 3 boot command with -serial file:$VMDIR/console.log appended — and read console.log to see how far it got.
• ssh actively refuses the key (vs. just timing out)? That means cloud-init never applied the seed. Confirm seed.iso is attached as a cdrom drive in the boot command (Step 3) and was built in Step 2, then re-boot.

5. One-time build-disk setup (disklabel, newfs, mount)

OpenBSD sees the second virtio disk as sd1. Give it a single 4.2BSD partition spanning the disk, newfs it, mount it at /build, and chown it to openbsd so the later rsync and build run without root. The printf drives the interactive disklabel -E editor (a a add partition, then default offset/size/type, w write, q quit) — it is fiddly and copied verbatim from CI. Run this once: newfs reformats, so re-running destroys whatever is on /build.

VMDIR=~/vms/openbsd-7.9
SSH="ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -i $VMDIR/vm_key -p 2222 openbsd@localhost"
$SSH /bin/sh <<'EOF'
set -e
printf 'a a\n\n\n\nw\nq\n' | doas disklabel -E sd1
doas newfs /dev/rsd1a
doas mkdir -p /build
doas mount /dev/sd1a /build
doas chown openbsd:wheel /build
df -h /build
EOF

If the doas commands here fail (permission denied, or doas prompts for a password), cloud-init's write_files never created /etc/doas.conf — the seed didn't apply. Don't retype the disk commands; nothing here works until doas does, so work through the Step 4 recovery (is the VM up? is seed.iso attached as a cdrom?) first.

6. Install deps + raise the datasize limit

doas pkg_add installs the build tools (the python%3/rsync-- spellings are correct — see Gotchas). Then raise the per-process datasize ceiling for the openbsd user — and treat this as intent, not a fixed substitution. OpenBSD's /etc/login.conf caps each process's data segment in the default login class (the class the openbsd user falls under), and the LLVM build needs roughly 4 GB, so both datasize-cur and datasize-max must end up at least 4096M (what CI sets). On the stock OpenBSD 7.9 image both default to 1536M, so the two seds below do it. But the goal is the 4096M ceiling, not the literal 1536M: if a future image ships a different default the seds match nothing, so read the current values (the trailing grep prints them) and, if either is below 4096M, raise it to 4096M directly — adjust the sed pattern or edit /etc/login.conf. Confirm both read 4096M before continuing; too low and the libs build dies with allocation failures partway through, far from this step. The edit persists on the root disk and re-running is a no-op.

VMDIR=~/vms/openbsd-7.9
SSH="ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -i $VMDIR/vm_key -p 2222 openbsd@localhost"
$SSH /bin/sh <<'EOF'
set -e
doas pkg_add -u && doas pkg_add cmake gmake git python%3 rsync--
# Raise the openbsd user's datasize cap to 4096M. The stock 7.9 image
# defaults both to 1536M; if a future image differs, the sed matches
# nothing — read the grep below and set both to 4096M however fits.
doas sed -i 's/datasize-max=1536M/datasize-max=4096M/' /etc/login.conf
doas sed -i 's/datasize-cur=1536M/datasize-cur=4096M/' /etc/login.conf
grep -E 'datasize-(cur|max)=' /etc/login.conf   # confirm both now read 4096M
EOF

7. Rsync the ponyc checkout in (exclude the host build/)

Run from your ponyc checkout. Exclude the top-level build/ (host artifacts; the VM builds its own — this --exclude is a deliberate divergence from CI, whose fresh checkout has none to skip). Keep .git (CMake runs git rev-parse). The vendored LLVM submodule under lib/llvm/src IS transferred — the VM needs it for the libs build.

VMDIR=~/vms/openbsd-7.9
rsync -az --exclude='/build' \
  -e "ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -i $VMDIR/vm_key -p 2222" \
  "$(git rev-parse --show-toplevel)/" openbsd@localhost:/build/ponyc/

Using the VM

The build uses OpenBSD's base clang — no CC/CXX/LD_LIBRARY_PATH exports (that is the DragonFly-only gcc13 dance). cmake -P lib/build-libs.cmake builds the vendored LLVM and is the multi-hour long pole — run it detached, then poll the log until it ends with libs DONE rc=0 (a nonzero rc means it failed — read the log above the marker). Keep -DJOBS=4 (what CI uses): each parallel compile is bounded by the 4096M datasize cap, so higher parallelism is the first thing to suspect on a libs out-of-memory.

VMDIR=~/vms/openbsd-7.9
SSH="ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -i $VMDIR/vm_key -p 2222 openbsd@localhost"
$SSH /bin/sh <<'EOF'
set -e
cat > /build/run-libs.sh <<'S'
#!/bin/sh
cd /build/ponyc && cmake -DJOBS=4 -P lib/build-libs.cmake
echo "libs DONE rc=$?"
S
chmod +x /build/run-libs.sh
nohup /build/run-libs.sh > /build/libs-build.log 2>&1 &
echo "libs building pid $!"
EOF
# poll until done: $SSH /bin/sh -c 'tail -3 /build/libs-build.log'  -> wait for "libs DONE rc=0"

Once libs is built (it persists in the VM), build and test with the same shell. Do not run this block until the poll shows libs DONE rc=0 — even cmake --preset debug needs the built LLVM (CMake's find_package(LLVM) fails without it), so it cannot run before the libs build:

VMDIR=~/vms/openbsd-7.9
SSH="ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -i $VMDIR/vm_key -p 2222 openbsd@localhost"
$SSH /bin/sh <<'EOF'
set -e
cd /build/ponyc
cmake --preset debug
cmake --build --preset debug
ctest --preset debug -L ci-core
EOF

To iterate on a fix: edit on the host, re-run Step 7's rsync (it's incremental — only changed files are sent), then re-run the build block above (long rebuilds should also be detached + polled). For exact CI parity, the tier-3 openbsd job (.github/workflows/ponyc-tier3.yml) runs more than this. In order: an unsupported-build-rejection smoke that runs before the libs build (it needs no LLVM — .ci-scripts/openbsd-reject-unsupported-builds.sh asserts use=address_sanitizer, thread_sanitizer, undefined_behavior_sanitizer, coverage, valgrind, and dtrace are each rejected with "not supported on OpenBSD"); then debug configure/build; a --static embedded-LLD link smoke (OpenBSD static is static-PIE, so the binary's file output reads "shared object" — the smoke instead asserts readelf -d shows no (NEEDED) entries); the debug ci-core suite; the self-hosted tool tests (pony-doc-tests/pony-lint-tests/ pony-lsp-tests); and a release build + the ci-core suite. Consult that job when validating a CI-matching issue.

Lifecycle

VMDIR=~/vms/openbsd-7.9; OPENBSD_VERSION=7.9; cd "$VMDIR"
pgrep -af "qemu-system-x86_64 -name openbsd-${OPENBSD_VERSION}"        # status
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -i vm_key -p 2222 openbsd@localhost   # interactive shell
# stop: kill the process. Disks persist for next time. The pgrep/pkill are scoped to this
# version so a second OpenBSD VM isn't matched; the pidfile path is per-$VMDIR anyway.
kill "$(cat openbsd.pid)" 2>/dev/null || pkill -f "qemu-system-x86_64 -name openbsd-${OPENBSD_VERSION}"

To restart later, re-run the step-3 boot command (the disks and installed deps persist; you do not redo setup). On a reboot, ssh-as-openbsd works immediately and doas still works (/etc/doas.conf persisted), and the raised datasize limit is still in /etc/login.conf — but the /build data disk is not auto-mounted (there is no /etc/fstab entry), so remount it before building: doas mount /dev/sd1a /build. The source under /build/ponyc is preserved on the data disk across the remount. For a long-lived VM, add the mount to /etc/fstab so it survives reboots.

How this relates to CI (don't re-add the CI-only steps)

This mirrors .ci-scripts/bsd/openbsd-provision.bash (the source of truth — keep this skill in sync if it changes). The local setup deliberately differs from CI, and each difference is safe:

• Skips CI host-bootstrap (free disk space, apt-get qemu, make /dev/kvm writable) — your host already has qemu and a usable hardware accelerator (Step 0 verified it).
• Persistent VM instead of built-fresh-and-killed per run.
• ssh adds -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR to quiet the host-key warning: a persistent VM reused on localhost:2222 collides with the stale known_hosts entry from a prior VM. CI's ephemeral runners never reuse the port, so openbsd-provision.bash doesn't bother.
• -smp 8 / -m 8G for build speed (CI uses 4 / 6G), and a -pidfile for the lifecycle commands.
• rsync --exclude='/build' to skip the host's build artifacts (CI's fresh checkout has none).
• No GHCR libs cache (that's token-gated CI plumbing) — you just run cmake -P lib/build-libs.cmake once.

The FreeBSD and DragonFly CI VMs follow the same shape (.ci-scripts/bsd/{freebsd,dragonfly}-provision.bash) and each has its own skill: create-freebsd-dev-env (also cloud-init, but base libc++/dtrace, an expect/su root bootstrap, and the source under /home/freebsd rather than a /build disk) and create-dragonfly-dev-env (gcc-only, and it drives a VGA console). This skill is OpenBSD-only; load a sibling if you need one of those.