The Arch fix in the previous commit was incomplete. 0.26.0-1 granted the host CAP_SYS_NICE through
every Linux channel we ship, and each one breaks KWin identification the same way:
* packaging/rpm/punktfunk.spec .......... %caps(cap_sys_nice=ep) in %files <- Fedora AND Bazzite
via rpm-ostree layering
* packaging/bazzite/build-sysext.sh ..... setcap on the staging tree, recorded by mksquashfs
* packaging/debian/build-deb.sh ......... setcap in the postinst
* packaging/nix/nixos-module.nix ........ security.wrappers with capabilities = "cap_sys_nice=ep"
* scripts/steamdeck/install.sh .......... setcap on $BIN, six lines after writing the .desktop
whose Exec= it thereby voids
Bazzite was NOT a separate fault, as first reported here — it is this one. Verified by mounting the
published punktfunk-0.26.0-1-x86-64.raw: `getcap usr/bin/punktfunk-host` reports cap_sys_nice=ep,
stored as security.capability in the squashfs. The claim in packaging/arch/build-sysext.sh that
"file capabilities don't survive this squashfs path" is false and is corrected here; mksquashfs
records them, which is exactly why the image shipped one.
NixOS deserves its own note: a security.wrappers entry does not dodge the problem. The wrapper
raises the capability into its AMBIENT set before exec'ing the store binary, precisely so it
survives — which lands CAP_SYS_NICE in the exec'd process's permitted set and fails the readlink
identically to a file capability. ExecStart now points at the store path directly, which is also the
path packages.nix substitutes into the .desktop's Exec=, so the two finally agree.
Measured blast radius of holding a capability, same-uid reader, CachyOS kernel 7.1.6:
/proc/PID/exe ....... EPERM <- KWin's identification. Desktop sessions die.
/proc/PID/root/* .... EPERM <- xdg-desktop-portal reads .flatpak-info here to resolve an
app id; the wlroots and Hyprland backends go through it
/proc/PID/environ ... EPERM
/proc/PID/cgroup .... OK
/proc/PID/status .... OK
/proc/PID/cmdline ... OK
Compositor backends, by exposure: KWin is broken outright (proven, field-confirmed). gamescope has
no identity gate and was never affected, which matches the field — only Desktop mode was reported.
Mutter drives Mutter's own D-Bus API, not the portal, and looks unaffected. wlroots and Hyprland go
through the ScreenCast portal, whose app-id resolution reads a path the capability blocks — a real
exposure, not something I reproduced end to end.
The sysext build now HARD-FAILS if a capability is staged, rather than trusting that the RPM payload
never carries one: a merged sysext's /usr is read-only squashfs, so a bad image cannot be repaired
on the box, and the spec was one %caps() away from baking one in again.
Docs corrected, because they advertised the capability as a feature:
* docs-site running-as-a-service "GPU scheduling priority" — rewritten: the host carries no
capability, why it must not, and how to clear a 0.26.0-1 install (Bazzite needs a new image)
* docs-site configuration.md — the PYROWAVE_QUEUE_PRIORITY row no longer claims the packages grant it
* packaging/bazzite/README.md — §6.5 still described the kde-desktop-setup.sh behaviour from
before it stopped writing KWIN_WAYLAND_NO_PERMISSION_CHECKS and started REMOVING it; plus a
note that 0.26.0-1 Desktop mode cannot be repaired in place
* packaging/arch/README.md — the false "capabilities don't survive the sysext" line
* CHANGELOG v0.26.0 PW1 — annotated with the 0.26.0-2 correction rather than rewritten, and the
owed PyroWave-under-load A/B now says it needs a gamescope-only box
Verified: bash -n on all five changed shell files; nix-instantiate --parse on nixos-module.nix and
packages.nix; the published 0.26.0-1 sysext mounted and its capability read; getcap on an uncapped
file exits 0 with empty output, so the new build assertion cannot false-positive.
punktfunk-host — Debian/Ubuntu package (apt)
punktfunk-host is published as a .deb to Gitea's Debian package registry in the public
unom org, so the Ubuntu hosts update with plain apt. CI (.gitea/workflows/deb.yml) builds
and publishes on every push to main (a rolling <next-minor>~ciN.g<sha> build — the base is
derived from the latest stable tag by scripts/ci/pf-version.sh — to the canary apt
distribution) and on vX.Y.Z tags (a clean X.Y.Z to the stable distribution, plus attached
to the unified Gitea Release). The two are separate apt distributions, so a stable box never jumps
to a canary build — see Release Channels. The repo line
below subscribes to stable; swap stable → canary for the latest main builds.
The same workflow also publishes punktfunk-web (the browser management console — pairing +
status) and punktfunk-client (the native GTK4/libadwaita Linux client). punktfunk-host Recommends
punktfunk-web, so a default apt install punktfunk-host pulls the console too (alongside the
udev/sysctl bits) unless you've disabled weak deps; punktfunk-client is independent — install it
on the box you stream to. (punktfunk-probe is the headless reference/test tool, not packaged
here.)
Package layout mirrors the Fedora RPM (../rpm/punktfunk.spec): the host binary, the /dev/uinput
udev rule, the systemd user unit, headless session helpers, the example config, and the OpenAPI
doc. Runtime Depends are computed by dpkg-shlibdeps from the binary itself. The NVIDIA driver
(libnvidia-encode / libEGL_nvidia / libcuda) is not a dependency — it's installed out of
band, like on the RPM side.
Ubuntu 24.04 LTS (and why it needs a special build)
punktfunk-host needs FFmpeg 8 (libavcodec62), but Ubuntu 24.04 LTS ships FFmpeg 6.1
(libavcodec60). So a host .deb built the obvious way — on the same Ubuntu 26.04 image as the
client (ci/rust-ci.Dockerfile) — declares Depends: libavcodec62, … and a glibc-2.41 floor that
24.04's apt can't satisfy ("the required packages are too recent"). To fix that, the host .deb is
instead built on an Ubuntu 24.04 image (ci/rust-ci-noble.Dockerfile) that carries a from-source
FFmpeg 8, and that FFmpeg is bundled into the package (build-deb.sh BUNDLE_FFMPEG=1 → the
libav* land in /usr/lib/punktfunk-host, the binary's rpath points there, and the libav* sonames are
dropped from Depends). The result is one host .deb that installs on Ubuntu 24.04 LTS through
26.04 (glibc floor 2.39; no distro-FFmpeg dependency). The client/web/scripting .debs still build
on 26.04 (the native client needs SDL3 / GTK4 ≥ 4.20, absent on 24.04) — install the client on the box
you stream to, which is independent of the host's distro.
Install on a host (one-time)
The registry is public, so no apt auth is needed — just trust the repo's signing key:
sudo install -d -m 0755 /etc/apt/keyrings
curl -fsSL https://git.unom.io/api/packages/unom/debian/repository.key \
| sudo tee /etc/apt/keyrings/punktfunk.asc >/dev/null
echo "deb [signed-by=/etc/apt/keyrings/punktfunk.asc] https://git.unom.io/api/packages/unom/debian stable main" \
| sudo tee /etc/apt/sources.list.d/punktfunk.list
sudo apt update
sudo apt install punktfunk-host
Then, as the desktop user:
sudo usermod -aG input "$USER" # virtual gamepads (re-login to take effect)
mkdir -p ~/.config/punktfunk
cp /usr/share/punktfunk-host/host.env.example ~/.config/punktfunk/host.env # then edit
systemctl --user enable --now punktfunk-host
# Web console — enable it and read the auto-generated login password (then open https://<host-ip>:47992):
systemctl --user enable --now punktfunk-web
journalctl --user -u punktfunk-web-init | sed -n 's/.*password generated: //p'
Firewall
Debian ships no firewall and Ubuntu's ufw is installed-but-inactive by default, so out of the
box there is nothing to open. If you turn one on, the punktfunk-host package ships a one-liner
opener for both ufw and firewalld (neither auto-enabled):
# ufw (Ubuntu) — profile at /etc/ufw/applications.d/punktfunk, read at once (no reload):
sudo ufw allow punktfunk-native # the default native host
sudo ufw allow punktfunk-gamestream # …add for Moonlight compat
# firewalld — service definitions at /usr/lib/firewalld/services/:
sudo firewall-cmd --reload # load the installed definition
sudo firewall-cmd --permanent --add-service=punktfunk-native
# --add-service=punktfunk-gamestream # …add for Moonlight compat
sudo firewall-cmd --reload
If you installed the web console (punktfunk-web) and want it reachable from another device,
open its port with the matching one-liner — sudo ufw allow punktfunk-web or sudo firewall-cmd --permanent --add-service=punktfunk-web && sudo firewall-cmd --reload — which opens TCP 47992
(HTTPS, login-gated). The mgmt API (47990) is opened for paired clients by the punktfunk-native
profile (game-library browsing over mTLS); off-loopback it serves only read-only status/library and
keeps admin loopback-only.
Prefer explicit rules? Open the ports directly. The native punktfunk/1 plane:
- QUIC control plane: UDP 9777 (
serve --native-port Nto change). - Data plane: a separate UDP port. By default it's random — the host binds
0.0.0.0:0and tells the client which port it got. Video flows host → client, but the client sends the first packet (a hole-punch), so the host learns the client's real source and streams back — this traverses NAT / inter-VLAN with no forwarded port. You normally don't open it: if a deny-inbound firewall drops the punch, the host waits ~2.5 s and falls back to the client-reported address, and a stateful firewall then admits the return (it just adds ~2.5 s to session start). To skip that delay, pin it withserve --data-port <PORT>(orPUNKTFUNK_DATA_PORT): the host binds that fixed port and streams direct (no punch-wait) — open exactly that one port. A fixed port serves one session at a time (concurrent ones fall back to random + hole-punch), and direct mode needs the client's reported address to be reachable (flat LAN / a non-remapping port-forward).
And the GameStream / Moonlight ports (fixed) — only needed if you run the host with
serve --gamestream (opt-in, trusted LAN only); bare serve is native-only and doesn't open these:
| Port | Proto | Purpose |
|---|---|---|
| 47984 | TCP | HTTPS nvhttp (paired, mutual-TLS) |
| 47989 | TCP | HTTP nvhttp (/serverinfo, /pair PIN flow) |
| 48010 | TCP | RTSP handshake |
| 47998–48010 | UDP | Video RTP (+ FEC), ENet control (47999), audio (48000) |
| 5353 | UDP | mDNS auto-discovery |
The mgmt API (TCP 47990, HTTPS + mTLS) binds all interfaces by default so paired clients can browse the
game library — the punktfunk-native profile opens it. Off-loopback it serves only read-only
status/library to a paired client cert; the admin surface stays loopback-only. Pass
--mgmt-bind 127.0.0.1:47990 to keep it loopback-only (then leave 47990 closed).
With ufw (explicit ports, instead of the shipped profile):
sudo ufw allow 9777/udp # punktfunk/1 control plane
sudo ufw allow 47990/tcp # mgmt/library API (HTTPS + mTLS; LAN = read-only, paired)
sudo ufw allow 47984/tcp && sudo ufw allow 47989/tcp && sudo ufw allow 48010/tcp
sudo ufw allow 47998,47999,48000/udp # GameStream video/control/audio
sudo ufw allow 5353/udp # mDNS discovery
# The punktfunk/1 data plane uses a random UDP port; leave it closed on a LAN — the host hole-punches
# and falls back (~2.5s at session start if firewalled). To skip that, pin it: `serve --data-port
# 9778` and `ufw allow 9778/udp`.
With raw nftables (add to your inet filter input chain):
udp dport 9777 accept # punktfunk/1 control plane
tcp dport 47990 accept # mgmt/library API (HTTPS + mTLS; LAN = read-only, paired)
tcp dport { 47984, 47989, 48010 } accept
udp dport { 47998-48010, 5353 } accept
# The punktfunk/1 data plane is a random UDP port — normally left closed (hole-punch + ~2.5s
# fallback). Pin it with `serve --data-port <PORT>` to open exactly one instead.
Updates
sudo apt update && sudo apt upgrade # picks up the newest published build
systemctl --user restart punktfunk-host # if the unit was already running
Build a .deb locally
VERSION=0.0.1 bash packaging/debian/build-deb.sh # -> dist/punktfunk-host_0.0.1_amd64.deb
Needs dpkg-dev (dpkg-shlibdeps, dpkg-deb). It builds the release binary first if missing.
Building on a GPU box is fine — the NVIDIA driver lib is filtered out either way.
That plain invocation hard-depends on the build box's system FFmpeg, so it only installs on a box with the same libav* soname. For the universal package CI ships (installs on 24.04 LTS → 26.04), build it in the noble image with FFmpeg bundled:
docker build -f ci/rust-ci-noble.Dockerfile -t pf-noble ci
docker run --rm -v "$PWD:/src" -w /src pf-noble \
bash -lc 'VERSION=0.0.1 BUNDLE_FFMPEG=1 bash packaging/debian/build-deb.sh'
BUNDLE_FFMPEG=1 needs patchelf and an FFmpeg install at FFMPEG_PREFIX (default /opt/ffmpeg,
which the noble image provides).
The arm64 client .deb
The client also ships for arm64 (punktfunk-client_<version>_arm64.deb, published to the same
apt distribution — the registry keys pool entries by architecture, so an arm64 box needs no extra
configuration). There is no arm64 host package: the Linux host encodes with NVENC/QSV/AMF, all
x86.
It is cross-compiled on an ordinary amd64 machine in ci/rust-ci-arm64cross.Dockerfile — the
rust-ci toolchain plus an Ubuntu ports arm64 multiarch sysroot. No arm64 runner is involved:
docker build -f ci/rust-ci-arm64cross.Dockerfile -t pf-arm64cross . # repo-root context
docker run --rm -v "$PWD:/w" -w /w pf-arm64cross \
bash -lc 'VERSION=0.0.1 ARCH=arm64 TARGET=aarch64-unknown-linux-gnu \
bash packaging/debian/build-client-deb.sh'
TARGET moves the binaries to target/<triple>/release; ARCH sets the package's
Architecture: field. Set both — one without the other builds an amd64 binary into a package
labelled arm64, or vice versa. dpkg-shlibdeps reads the arm64 sonames straight out of the
multiarch sysroot, so Depends: comes out right with no manual list.