enricobuehler
42ee6c5628
0.26.0-1 setcap'd `cap_sys_nice=ep` on /usr/bin/punktfunk-host so the encoder could open an
elevated global-priority Vulkan queue. On every KDE box that ended desktop streaming outright:
KWin virtual output failed: KWin does not expose zkde_screencast_unstable_v1 to this client
reported from CachyOS on NVIDIA and on AMD, surviving a clean reinstall of host and client, and
worked around only by KWIN_WAYLAND_NO_PERMISSION_CHECKS=1.
The two cannot coexist. KWin hands out its restricted protocols — zkde_screencast_unstable_v1,
which mints our virtual output, and org_kde_kwin_fake_input, which injects input — only to a client
it can IDENTIFY, by resolving that client's /proc/<pid>/exe and matching it against an installed
.desktop's Exec=. The kernel refuses that readlink to any reader whose effective set is not a
superset of the target's PERMITTED set (cap_ptrace_access_check), and KWin holds no capabilities.
So the instant the binary carries one, KWin's executablePath() is empty, nothing matches, and the
global is never advertised — presenting exactly as a missing or mis-installed .desktop file.
Measured on CachyOS (kernel 7.1.6), same-uid reader, cap_sys_nice=ep on the target:
no capability .............................. readlink /proc/<pid>/exe OK
capability ................................. EPERM
capability + prctl(PR_SET_DUMPABLE, 1) ..... EPERM <- dumpable is NOT the gate
capability dropped + PR_SET_DUMPABLE(1) .... OK <- only an uncapped process works
The third row also rules out the reflex fix of moving the grant to systemd AmbientCapabilities=,
which lands CAP_SYS_NICE in the very same permitted set. Nothing short of not holding the
capability restores identification, so the host does not get one.
The cost is pacing only. pf-zerocopy's device create already walks REALTIME -> HIGH -> default when
a priority class is refused, and pf-frame's thread nice is a documented best-effort no-op without
the capability — so this is 0.25.0's behaviour exactly, which is the behaviour that worked.
* packaging/arch/punktfunk-host.install: grant -> revoke. post_upgrade strips the capability from
boxes that already ran 0.26.0-1's scriptlet. A pacman upgrade writes a new inode and file
capabilities do not survive that, so this is belt-and-braces for reinstall/downgrade paths.
* pf-vdisplay kwin.rs: all three "KWin does not expose zkde_screencast" errors now read
/proc/self/status and, if this process holds ANY capability, name it with its CapPrm mask and
the `setcap -r` that repairs it. The failure stays impossible to diagnose from the Wayland side
otherwise, and it is not unique to our own packaging — a hand-rolled setcap does it too.
Verified on 192.168.1.21 (CachyOS): the capability/dumpable matrix above; cargo check and
cargo clippy --all-targets -- -D warnings clean for pf-vdisplay; both new unit tests pass; and the
hint itself exercised end-to-end, silent uncapped and firing with CapPrm=0x0000000000800000 under
cap_sys_nice=ep. The shipped punktfunk-host-0.26.0-1-x86_64.pkg.tar.zst was unpacked to confirm its
.INSTALL carries the setcap on both post_install and post_upgrade.
Ships as 0.26.0-2 — packaging plus one crate, no version bump.
Packaging punktfunk for Fedora / Bazzite
The punktfunk host links system FFmpeg (NVENC on NVIDIA, VAAPI on AMD/Intel, with a GPU-less software-H.264 fallback), PipeWire and Opus. This page covers packaging it for the Fedora Atomic / Bazzite world (rpm-ostree + bootc), where most of those deps are already present; the NVIDIA-specific notes below apply to the NVENC path.
👉 Ubuntu/Debian hosts install via
aptfrom Gitea's package registry — seedebian/README.md(apt update && apt upgradefor new builds).
👉 End-to-end Bazzite setup walkthrough (install → udev/group →
host.env→ service → firewall → verify → troubleshooting):bazzite/README.md. This file is the higher-level packaging rationale.
packaging/
rpm/punktfunk.spec # the RPM (builds punktfunk-host from source with cargo)
bazzite/host.env # gamescope-default config for a Bazzite appliance
bazzite/README.md # step-by-step Bazzite setup guide
bazzite/*sysext*.sh # the no-layering path: build/install/publish the systemd-sysext
bootc/Containerfile # bake punktfunk into a Bazzite-based atomic image
copr/ # COPR build-from-SCM settings
The other packaging targets have their own READMEs: debian/ (apt),
arch/ (pacman binary repo + PKGBUILD + SteamOS sysext),
flatpak/ (the client), windows/ (host installer +
drivers), plus kde/ and linux/ helpers. NixOS / Nix users get a flake (flake.nix at the
repo root) with reproducible host + client packages and a services.punktfunk NixOS module —
see nix/README.md.
What's needed beyond base Fedora
| Dependency | Where it comes from |
|---|---|
ffmpeg-libs with NVENC |
RPM Fusion nonfree (ffmpeg, not ffmpeg-free) |
NVIDIA driver (libnvidia-encode, libEGL_nvidia) |
Bazzite -nvidia images ship it; plain Fedora: akmod-nvidia + xorg-x11-drv-nvidia-cuda |
| gamescope, PipeWire, wireplumber | Bazzite ships these; plain Fedora: dnf install gamescope pipewire wireplumber |
opus, libei |
Fedora base / updates |
On Bazzite the only genuinely new runtime bits are ffmpeg-libs (RPM Fusion) + opus +
libei — the rest of the stack is already there. The default backend is gamescope
(packaging/bazzite/host.env), which the host spawns headless per session — no desktop login.
Option A — systemd-sysext (recommended; no layering, no reboot)
On Bazzite / Fedora Atomic the recommended install is the systemd-sysext image — rpm-ostree
layering is a last resort per the Bazzite docs (it slows every OS update and can block upgrades),
while a sysext overlays /usr at runtime, survives OS updates, and updates in one command with
no reboot. CI wraps the same RPMs below into the image, so content and channels are identical.
curl -fsSLO https://git.unom.io/unom/punktfunk/raw/branch/main/packaging/bazzite/punktfunk-sysext.sh
sudo bash punktfunk-sysext.sh install # then: sudo punktfunk-sysext update | status | remove
Full walkthrough (incl. the F43→F44 rebase behavior and migration off layering):
bazzite/README.md.
Option B — Gitea RPM registry (per-host, rpm-ostree layering)
The host's RPM is published to unom's self-hosted Gitea RPM registry (CI builds it on every
push), mirroring the Debian/apt setup. Add one repo file, install, and track
updates with rpm-ostree upgrade — no COPR account needed. Full guide: rpm/README.md.
# GPG-signed pkgs + Gitea-signed metadata → gpgcheck=1, repo_gpgcheck=1 (see rpm/README.md)
sudo tee /etc/yum.repos.d/punktfunk.repo >/dev/null <<'REPO'
[gitea-unom-bazzite]
name=punktfunk (unom, Bazzite)
baseurl=https://git.unom.io/api/packages/unom/rpm/bazzite
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://git.unom.io/api/packages/unom/rpm/repository.key
https://git.unom.io/api/packages/unom/generic/punktfunk-keys/1/RPM-GPG-KEY-punktfunk
REPO
rpm-ostree install punktfunk && systemctl reboot
# updates: rpm-ostree upgrade && systemctl reboot
Option C — COPR (per-host, rpm-ostree install)
- Create a COPR project, enable build-from-SCM pointing at this repo, spec path
packaging/rpm/punktfunk.spec(seecopr/README.md). Under External Repositories add RPM Fusion nonfree soffmpeg-develresolves at build time. - On the Bazzite host:
# RPM Fusion (for the NVENC ffmpeg) — usually already enabled on Bazzite rpm-ostree install \ https://mirrors.rpmfusion.org/free/fedora/rpmfusion-free-release-$(rpm -E %fedora).noarch.rpm \ https://mirrors.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-$(rpm -E %fedora).noarch.rpm # enable the COPR + install punktfunk sudo wget -O /etc/yum.repos.d/_copr_punktfunk.repo \ https://copr.fedorainfracloud.org/coprs/enricobuehler/punktfunk/repo/fedora-$(rpm -E %fedora)/ rpm-ostree install punktfunk systemctl reboot
Option D — bootc (image-based, atomic)
Layer punktfunk into a Bazzite image once, then rebase any number of hosts onto it — no
per-host drift. See bootc/Containerfile:
podman build -t ghcr.io/<you>/bazzite-punktfunk -f packaging/bootc/Containerfile .
podman push ghcr.io/<you>/bazzite-punktfunk
# on the target:
sudo bootc switch ghcr.io/<you>/bazzite-punktfunk && systemctl reboot
First-run setup (all options)
ujust add-user-to-input-group # virtual gamepads need /dev/uinput (then re-login).
# On Bazzite use ujust, NOT `usermod -aG input` (atomic OS — it won't stick).
mkdir -p ~/.config/punktfunk
cp /usr/share/punktfunk/host.env.bazzite ~/.config/punktfunk/host.env # edit (gamescope app, etc.)
systemctl --user enable --now punktfunk-host
# Management web console (pairing + status) — pulled in by default (the host RPM Recommends it;
# `--no-install-recommends` / headless-only boxes can skip it). Enable it and read the login password:
systemctl --user enable --now punktfunk-web
journalctl --user -u punktfunk-web-init | sed -n 's/.*password generated: //p' # then open https://<host-ip>:47992
Pair a stock Moonlight client (mDNS-discovered), or connect the native punktfunk/1 client — via the
web console at https://<host-ip>:47992 or directly.
⚠️ COPR caveat: COPR's mock chroot has no
bun, so a COPR build produces onlypunktfunk+punktfunk-client— notpunktfunk-web. For the console on a COPR/bootc host, install from the Gitea RPM registry (Option B — it carriespunktfunk-web; the sysext image includes it too), which is also whybootc/Containerfileinstalls from there rather than COPR.
Why not Flatpak (for the HOST)?
The host needs unsandboxed access the zero-copy NVENC path, /dev/uinput, the PipeWire
graph and the compositor's privileged protocols — a Flatpak sandbox fights all of these.
An RPM (or the bootc layer) installs into the host system where those just work.
👉 The client is a different story — it IS shipped as a Flatpak (the only viable Steam Deck install path: SteamOS
/usris read-only and lackslibadwaita/libSDL3). Seeflatpak/README.md. The client sandbox only needs the GPU render node, Wayland, PipeWire audio, the network and hidraw — all expressible as finish-args.
Building the SRPM/RPM locally (Fedora only)
git archive --format=tar.gz --prefix=punktfunk-0.3.0/ -o ~/rpmbuild/SOURCES/punktfunk-0.3.0.tar.gz HEAD
rpmbuild -ba packaging/rpm/punktfunk.spec # needs the BuildRequires from the spec
# (0.3.0 = the spec's default %{pf_version}; the prefix and tarball name must match it)
(Not buildable on Debian/Ubuntu — use a Fedora toolbox/container or COPR.)