NixBSD Image

NB-01 // DECLARATIVE BUILD

omfreebdy normally installs the imperative way — pkg install, copy configs, enable services in rc.conf. The NixBSD image is the same desktop expressed declaratively: one Nix flake that pins every package, config file, script, and service, then cross-compiles the whole thing from a Linux box and boots it as a NixBSD virtual machine — a real FreeBSD 15 kernel and userland, managed NixOS-style.

No FreeBSD machine is touched to build it. nix build on Linux produces a bootable x86_64-unknown-freebsd image with the i3 desktop, the omfreebdy theme set, every user script, and a full CLI/dev toolchain baked in.

The Nix-built omfreebdy i3 desktop, rendered live on a FreeBSD 15 NixBSD VM — gruvbox wallpaper, i3 + status bar, and fastfetch reporting the FreeBSD kernel, all cross-built from a single declarative flake on Linux. Theme switched live with theme-set gruvbox.

TL;DR

# cross-build the image from Linux (uses the cppnix evaluator + nixbsd cache)

$ nix build .#omfreebdy-x11-vm

# boot it under QEMU

$ ./result/bin/run-omfreebdy-vm

What This Is

Kernel	NB-K	FreeBSD 15.0-RELEASE	Real BSD kernel + userland, not Linux
Management	NB-M	NixBSD	NixOS-style declarative config on the BSD kernel
Desktop	NB-D	i3 / X11	i3 + i3status + picom + rofi, all 18 themes
Build host	NB-B	Linux → FreeBSD	Cross-compiled; no FreeBSD machine needed
Render path	NB-R	Xvfb (software)	Headless X server — no GPU or DRM required
Output	NB-O	QEMU VM image	Boots straight to the desktop over VNC

The imperative pkg-based install is still the primary way to run omfreebdy on real hardware. The NixBSD image is a parallel, reproducible build target — handy for VMs, CI, and proving the whole stack assembles from a single source of truth.

What Works

The image isn’t a stripped-down demo — it reproduces omfreebdy’s actual install: every script in bin/, the full config tree, the user shell, services, and a real toolchain.

Layer	Included
Window manager	i3, i3status, picom, rofi, xterm + st
Wallpaper	xwallpaper paints the catppuccin background on the Xvfb root
Themes	All 18 omfreebdy themes (catppuccin, gruvbox, everforest, kanagawa, …)
Scripts	The complete bin/ set — theme-set, theme-list, every helper
Configs	Seeded verbatim from config/ into ~/.config on first boot
CLI tools	btop, fastfetch, starship, tmux, zoxide, fzf, eza, bat, fd, jq, ripgrep, lazygit, gh, dust, …
Dev toolchain	Go, Python 3.11, Node 22, Ruby, GNU Make, ImageMagick
Login	Autologin getty → user shell → X session

How To Change Themes

Identical to the rest of omfreebdy — the theme scripts ship in the image:

# list available themes

$ theme-list

# switch the whole desktop instantly

$ theme-set gruvbox

theme-set rewrites the i3, i3status, picom, and rofi colors and reloads them — exactly as on a pkg-installed system. See the Themes guide for authoring your own.

Building It

The build runs entirely on Linux. Two non-obvious pieces make the FreeBSD cross-compile work:

Evaluator	CPP	cppnix	The rhelmot/nix fork — stock Nix infinite-recurses on the FreeBSD stdenv bootstrap
Cache	SUB	nixbsd attic	Pre-built FreeBSD bootstrap from the NixBSD project’s binary cache

# the flake exposes the VM as a Linux package output

$ nix build .#packages.x86_64-linux.omfreebdy-x11-vm

# run it — QEMU boots the FreeBSD VM, X session comes up over VNC

$ ./result/bin/run-omfreebdy-vm

# connect a VNC viewer to the forwarded port to see the desktop

$ vncviewer 127.0.0.1:5900

The flake also exposes .#omfreebdy-wayland-vm (the Hyprland profile). It builds and boots, but Hyprland needs a real GPU to render — see the journey below.

The Cross-Compile Journey

Getting omfreebdy onto a FreeBSD kernel from a Linux builder meant teaching nixpkgs a handful of FreeBSD facts. None of these are omfreebdy bugs — the same software builds cleanly on real FreeBSD via pkg. The gap is purely nixpkgs’ Linux-centric cross-packaging.

Wayland first — and the GPU wall

The first target was the real Hyprland desktop. It cross-compiled completely — mesa/llvmpipe, aquamarine, Hyprland 0.53.1, foot, fuzzel, swaybg, polkit, seatd — and booted, reading its activation-seeded hyprland.conf and bringing up its full manager stack.

Hyprland booting on the FreeBSD-kernel VM — it builds every manager, then dies at GPU init.

Then it hit a hard wall: aquamarine’s only buffer allocator is GBM, which requires a DRM render node (/dev/dri/renderD*). FreeBSD 15 in QEMU has no virtio-gpu KMS driver, so there’s no /dev/dri at all — Cannot open backend: no allocator available. This isn’t a packaging bug; it needs real GPU hardware with drm-kmod. So for the VM we pivoted to omfreebdy’s i3/X11 profile, which software-renders under Xvfb with no GPU.

The versionless triple

nixpkgs targets FreeBSD with the versionless triple x86_64-unknown-freebsd — the clang-standard NixBSD identity. That’s the platform’s identity; changing it would rebuild the entire package set. Most things accept it; the GNU toolchain’s config.gcc doesn’t (it extracts FBSD_MAJOR from the triple and aborts when there’s no version). A one-line patch defaults it to 15.

Trimming Linux-only dependencies

A scattering of packages pull deps that exist only on Linux (or are glibc-compat shims). Each is a peripheral feature, not a core component — so the fix is to drop the dep, not the package:

• i3status — drop the libnl (network) and pulseaudio (volume) modules; time/cpu/disk/load stay.
• i3 — drop the Perl X11::XCB/Inline::C helper-script stack; the WM binary doesn’t need it.
• scrot — drop libbsd (a glibc strlcpy shim; FreeBSD libc already has it).
• plocate — drop systemd (only used to place a .timer unit).
• feh — use plain imlib2, supply a strverscmp implementation, re-expose BSD extensions with -D__BSD_VISIBLE=1.
• fftw (via ImageMagick) — drop its optional Fortran interface; the C FFT library needs no Fortran.
• btop / dust / bat — add FreeBSD’s libproc / libgeom.
• gh — disable cgo. ripgrep — skip the install-check that runs the target binary on the Linux builder.

Three NixBSD fixes so the unmodified omfreebdy config just works

The goal was to run omfreebdy’s actual config unchanged — fix NixBSD, don’t fork the desktop:

1. /bin/sh must be ash — NixBSD points /bin/sh at bash, but FreeBSD’s wordexp(3) (used by i3’s include, exec, and status_command) needs the real ash shell. Set environment.binsh to freebsd.bin’s sh.
2. Locale data — NixBSD defaults LANG=en_US.UTF-8 but ships no /usr/share/locale, so setlocale() fails → i3status exits and rofi segfaults. Point PATH_LOCALE at freebsd.locales.
3. ~/.cache — rofi segfaults writing its run/drun history to a missing cache dir; create it and set XDG_CACHE_HOME.

Deferred

A few things build on FreeBSD via pkg but aren’t cross-packaged in nixpkgs yet. They’re tracked, not abandoned — the genuine frontier is cross-compiling compilers.

Item	Why deferred
gfortran / OpenBLAS	The cross-GCC nixpkgs builds is glibc-wired — no FreeBSD libc. The config.gcc triple patch is a correct starting point but not sufficient on its own.
flang	LLVM Fortran cascades into MLIR cross-build scope surgery (cross mlir-tblgen).
rustc	Bootstrap stage runs a target binary on the Linux builder.
neovim	Runs the freshly-built nvim during its own build.

None of these block the desktop or the CLI/dev toolchain. They’re follow-ups in nixpkgs’ FreeBSD cross-compilation support — the software itself runs fine on FreeBSD today.