enricobuehler
f26d21125d
Rewrites the "GPU scheduling priority" section around the split: punktfunk-encode-worker carries
cap_sys_nice=ep, punktfunk-host carries nothing on any channel, ever. The KWin identification
mechanism is spelled out in plain words and the failure line is quoted verbatim
("KWin does not expose zkde_screencast_unstable_v1 to this client") so someone searching for their
symptom lands on the explanation.
The warning names all three ways an operator would reach for the capability — hand setcap, a systemd
AmbientCapabilities= line, a NixOS security.wrappers entry — because all three put it in the same
permitted set and all three cost KDE desktop streaming. That is the failure mode that made this
worth documenting: it looks exactly like a missing .desktop and survives reinstalling both ends.
configuration.md gains PUNKTFUNK_ENCODE_WORKER (path, or `off` to force the in-process encoder) and
re-describes PYROWAVE_QUEUE_PRIORITY as an intent forwarded to whichever process does the encode.
kde.md gains one line on the troubleshooting bullet someone actually lands on: getcap on the host
must print nothing.
The published 0.26.0 notes are deliberately untouched — they are the record of what shipped. The
flipped phrasing lives in v0.27.0's notes instead; v0.26.0.md:37 ("a system privilege that turns out
to stop KDE recognising the host at all") is the line that goes stale when this ships.
151 lines
7.6 KiB
Markdown
151 lines
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---
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title: KDE Plasma (KWin)
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description: Configure a Punktfunk host for KDE — host.env, quirks, and a headless KWin session.
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---
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Configure a Punktfunk host on **KDE Plasma**. The host uses KDE's KWin compositor to create a
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per-client virtual display, captured zero-copy on the GPU (NVIDIA, AMD and Intel alike). This page
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assumes the package is already installed — see [Ubuntu](/docs/ubuntu), [Fedora](/docs/fedora),
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[Arch](/docs/arch), or the
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[Bazzite](/docs/bazzite) appliance.
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> New here? Read [Security & Safe Use](/docs/security) first — a streaming host is remote control of
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> the machine, so keep it on a trusted LAN or VPN and require pairing.
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## host.env
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The host auto-detects your KWin session on every connect — including a box that switches between
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the Plasma desktop and Steam Game Mode — so the starter `~/.config/punktfunk/host.env` is one line:
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```ini
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# ~/.config/punktfunk/host.env (keys are case-sensitive)
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PUNKTFUNK_VIDEO_SOURCE=virtual
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# GPU zero-copy capture→encode (dmabuf → CUDA/NVENC on NVIDIA, dmabuf → Vulkan Video or VAAPI on
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# AMD/Intel) is ON by default; auto-falls back to CPU. Set PUNKTFUNK_ZEROCOPY=0 to force CPU.
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```
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> **Don't set `PUNKTFUNK_COMPOSITOR`, `WAYLAND_DISPLAY`, or `XDG_CURRENT_DESKTOP` here.** Pinning
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> the compositor turns auto-detection **off** — per connect *and* mid-stream — so a switch to Game
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> Mode then kills the stream instead of being followed, and stale session values point the host at
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> dead sockets. Forcing a backend is for CI and dedicated appliances (the
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> [headless session](#headless-session) below ships a `host.env.kde` that pins on purpose).
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If the box switches between the desktop and Game Mode, also enable lingering — the host is a user
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service, and without linger the logout moment of a session switch tears it (and PipeWire) down
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mid-stream:
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```sh
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sudo loginctl enable-linger "$USER"
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```
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See the [Configuration reference](/docs/configuration) for every option.
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## Use a Wayland session
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KDE must run on **Wayland**, not X11 — pick the Wayland session from the picker on the login screen.
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The virtual-display path is Wayland-only and will not come up under X11.
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On a normal Plasma login KWin drives your real hardware, and **any Plasma 6 release** can create the
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virtual output — what it needs is the screencast grant below, not a particular version. The
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[headless session](#headless-session) further down is the exception: it runs
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`kwin_wayland --virtual`, and *that* backend only learned to create virtual outputs in
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**KWin 6.5.6**, so an appliance box needs 6.5.6 or newer. Check with:
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```sh
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kwin_wayland --version
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```
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## Streaming the interactive desktop
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To stream a logged-in Plasma desktop (rather than a headless session, below), KWin has to hand the
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host its restricted screencast protocol. The host package ships an `io.unom.Punktfunk.Host.desktop`
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file whose `X-KDE-Wayland-Interfaces` grants exactly that on a normal interactive session
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(least-privilege, the same mechanism krfb/krdp use). After a **fresh install, log out and back into
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the Desktop session once** so KWin re-reads the grant.
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**Input needs no extra setup.** That same `.desktop` file also grants `org_kde_kwin_fake_input`, so
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the host injects keyboard, mouse and touch straight into KWin — no portal, and no "Allow remote
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control?" dialog for a headless box to answer, on every distro. All a fresh install needs is the log
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out and back in above, so KWin re-reads the grant.
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The old RemoteDesktop-portal grant only matters now if you force the libei input backend
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(`PUNKTFUNK_INPUT_BACKEND=libei`) — that one injects through the RemoteDesktop portal, and on KDE it
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is also what a portal capture (`PUNKTFUNK_VIDEO_SOURCE=portal`) is anchored to, so the capture
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inherits the same grant. To seed it, Fedora and Bazzite ship a one-shot helper (run once as the
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streaming user, no root); the `.deb` and Arch packages don't include that wrapper, so copy the
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shipped `kde-authorized` file into the portal store by hand instead (the share dir is
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`/usr/share/punktfunk-host` on Ubuntu, `/usr/share/punktfunk` on Arch) and log out and back
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in:
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```sh
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bash /usr/share/punktfunk/bazzite/kde-desktop-setup.sh # Fedora / Bazzite
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mkdir -p ~/.local/share/flatpak/db # Ubuntu / Arch
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cp /usr/share/punktfunk*/headless/kde-authorized ~/.local/share/flatpak/db/kde-authorized
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```
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A login-less appliance skips all of this — its headless session (below) needs none of these grants.
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## Start the host
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With `host.env` in place, start the host from **inside your Plasma session**:
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```sh
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systemctl --user enable --now punktfunk-host
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journalctl --user -u punktfunk-host -f # watch it come up and print its identity fingerprint
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```
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This unit runs `serve --gamestream`, so it serves stock [Moonlight](/docs/moonlight) clients as well
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as the native ones. For a native-only host, see
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[What the unit starts](/docs/running-as-a-service#what-the-unit-starts).
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A desktop-login host should also follow your session's lifetime, or restarting Plasma leaves the host
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wired to a compositor that is gone — it keeps answering, and every session after that fails at
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capture. Add the drop-in from
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[Restart the host with your desktop](/docs/running-as-a-service#restart-the-host-with-your-desktop).
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Skip it on the headless appliance route below.
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Then bring up [The Web Console](/docs/web-console) to arm pairing and connect a
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[client](/docs/clients). To start at boot — including fully headless — see the
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[headless session](#headless-session) below or [Running as a Service](/docs/running-as-a-service).
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## Persistent per-client scaling
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KWin round-trips per-client display scale: it names each session's virtual output per client, so a
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scale you set for one client (150 %, 125 %, …) is reapplied on that client's next connect. See
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[Virtual displays](/docs/virtual-displays).
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## Headless session
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For a login-less appliance — a box that streams at boot with no graphical login — the host brings up a
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**dedicated headless KWin session** rather than relying on an interactive one. It runs its own
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`kwin --virtual` session (shipped as the `punktfunk-kde-session.service` unit) with permission checks
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relaxed, so it needs none of the interactive grants above.
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```sh
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mkdir -p ~/.config/punktfunk
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cp /usr/share/punktfunk/host.env.kde ~/.config/punktfunk/host.env # Ubuntu: /usr/share/punktfunk-host/host.env.kde
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systemctl --user daemon-reload
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systemctl --user enable --now punktfunk-kde-session punktfunk-host
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sudo loginctl enable-linger "$USER"
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```
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The session unit brings up headless KWin; the host unit follows it and starts listening. See
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[Running as a Service](/docs/running-as-a-service) for the full headless setup.
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## Troubleshooting
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- **KWin isn't handing over the screencast protocol:** run `punktfunk-host probe-compositor` from
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inside the session. It exits 0 only when KWin is up *and* advertising the grant to the host, and
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prints the reason when it isn't — after a fresh install that is usually just the missing log out
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and back in. On the headless appliance session, also check `kwin_wayland --version` is ≥ 6.5.6.
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The other cause has nothing to do with the `.desktop` file: `getcap /usr/bin/punktfunk-host` must
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print **nothing at all**. A host binary carrying a Linux capability cannot be identified by KWin
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and is never offered the protocol, however correctly its grant is installed — see
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[GPU scheduling priority](/docs/running-as-a-service#gpu-scheduling-priority).
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- **Black screen / no picture:** confirm you're on a Wayland session (not X11) and, on NVIDIA, that
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the GL userspace is installed. More in [Troubleshooting](/docs/troubleshooting).
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To bring the console up and pair, see [The Web Console](/docs/web-console).
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