main-desktop/README.md

main-desktop

Custom Bazzite DX image for my desktop, built with BlueBuild, published to GHCR by GitHub Actions, and signed with cosign.

• Base: ghcr.io/ublue-os/bazzite-dx-nvidia — Bazzite DX, KDE Plasma, NVIDIA open kernel modules. There is no separate -open DX image anymore: DX NVIDIA is open-driver-only, which is exactly what the RTX 5090 (Blackwell) requires. Current stable ships driver 610.x (open).
• Pinned to Fedora 44 via image-version: stable-44 in recipes/recipe.yml. No surprise major upgrades; bump to stable-45 deliberately.
• This image layers almost nothing. The base already includes Steam and the gaming stack, Flatpak, Docker CE + CLI, Podman, VS Code, Homebrew, and nvidia-container-toolkit with automatic CDI setup (ublue-nvctk-cdi.service regenerates /etc/cdi/nvidia.yaml each boot). What this recipe adds: the cosign signature-verification policy and a declarative first-boot Flatpak set. That's it — by design.

Why BlueBuild instead of the raw Containerfile template: with the container toolkit already in-image, the whole custom layer is "install these Flatpaks on first boot + trust my signature", which the default-flatpaks and signing modules express declaratively in ~40 lines of YAML — no hand-rolled first-boot systemd unit needed.

One-time setup (before first push)

1. Create a GitHub repo and push this directory to it (main branch).

2. Generate the signing keypair in the repo root (press Enter for an empty password — the build action cannot use an encrypted key):

   cosign generate-key-pair
   

3. Store the private key as an Actions secret and commit only the public half:

   gh secret set SIGNING_SECRET < cosign.key
   git add cosign.pub && git commit -m "Add cosign public key" && git push
   

   cosign.key is git-ignored — never commit it.

4. The workflow (.github/workflows/build.yml) now builds on every push, on manual dispatch, and daily at 06:00 UTC (so base-image updates flow through automatically — this is what makes the image self-updating). Images publish to ghcr.io/<your-github-user>/main-desktop.

5. If the GHCR package ends up private, make it public in the package settings (Packages → main-desktop → Package settings → Change visibility), or rebasing will fail to pull.

Rebasing the desktop onto this image

From the existing Bazzite install, rebase in two steps — first unsigned (this installs the image, which contains the signing policy and public key), then signed:

# Step 1: unsigned rebase, then reboot
rpm-ostree rebase ostree-unverified-registry:ghcr.io/<your-github-user>/main-desktop:latest
systemctl reboot

# Step 2: switch to the signed ref, then reboot
rpm-ostree rebase ostree-image-signed:docker://ghcr.io/<your-github-user>/main-desktop:latest
systemctl reboot

After step 2, every update is signature-verified. :latest is fine here — the Fedora pin lives in the recipe, so latest never crosses a major until the recipe says so.

Roll back anytime with rpm-ostree rollback (or pick the previous deployment in the boot menu).

Install-time checklist

1. Driver sanity: nvidia-smi reports driver ≥ 580 (currently 610.x) and the RTX 5090 is listed. Confirm open kernel modules: modinfo -F license nvidia should say Dual MIT/GPL (the proprietary module says NVIDIA). Blackwell only works on the open modules.

2. Signature: verify the published image against the committed public key:

   cosign verify --key cosign.pub ghcr.io/<your-github-user>/main-desktop:latest
   

3. Deployment: rpm-ostree status shows the booted deployment is ostree-image-signed:docker://ghcr.io/<your-github-user>/main-desktop and the base version matches a recent build.

4. Flatpaks: the first-boot service installs the whole list below; give it a few minutes on first login (it notifies when done). Check with flatpak list --system.

5. Docker group: run ujust dx-group (adds you to docker and friends), then log out/in.

6. GPU in containers: see the section below — run the one-liner test.

GPU in containers (CUDA on the 5090)

nvidia-container-toolkit is already in the image and a boot service generates the CDI spec automatically. CDI is the shipped mechanism:

# Podman — works out of the box:
podman run --rm --device nvidia.com/gpu=all docker.io/nvidia/cuda:12.8.0-base-ubuntu24.04 nvidia-smi

# Docker — CDI device syntax also works on current Docker CE:
docker run --rm --device nvidia.com/gpu=all nvidia/cuda:12.8.0-base-ubuntu24.04 nvidia-smi

If you want the classic docker run --gpus all syntax, that needs a one-time runtime hookup (this writes to /etc/docker/daemon.json, which is mutable and survives updates):

sudo nvidia-ctk runtime configure --runtime=docker
sudo systemctl restart docker

First-boot Flatpaks

Installed system-wide from Flathub by the default-flatpaks module. All IDs verified against Flathub (2026-07).

Official / verified listings: Bambu Studio, Bitwarden, Discord, Firefox, Thunderbird, FreeCAD, GIMP, HandBrake, LibreOffice, Moonlight, PCSX2 (net.pcsx2.PCSX2 — the official build), Podman Desktop, Warzone 2100, XIVLauncher (dev.goats.xivlauncher).

Community / unverified listings — know what you're running:

App	ID	Note
GitHub Desktop	io.github.shiftey.Desktop	Community Linux fork; the "shiftey" spelling is the real ID
MakeMKV	com.makemkv.MakeMKV	Community packaging of the proprietary app
GeForce NOW	io.github.hmlendea.geforcenow-electron	Unofficial Electron wrapper, not an NVIDIA product
VLC	org.videolan.VLC	No verified badge on Flathub (still the VideoLAN-maintained build)
Godot	org.godotengine.Godot	No verified badge on Flathub

GeForce NOW on the 32:9 monitor: the service only streams 16:9 (and some 21:9) aspect ratios, so expect pillarboxing at 5120x1440 — that's a service limitation, not a config problem.

Post-install steps (manual by design — don't automate these)

PIA VPN — native WireGuard, not the app

The PIA desktop app installs into /usr and breaks on the read-only filesystem. Skip it:

1. Log in at PIA's OpenVPN config generator (or generate a WireGuard config via their API/support flow) and download configs for your preferred regions.
2. KDE System Settings → Network → Connections → Add (+) → Import VPN connection…, pick the downloaded file, and enter your PIA credentials.
3. This is plain NetworkManager — it lives in /etc, survives every update, and gets a connect/disconnect toggle in the system tray.

Microsoft Teams — PWA via Edge

No native Linux client. Install Microsoft Edge specifically (corporate conditional access / Intune compatibility): flatpak install flathub com.microsoft.Edge, sign in to https://teams.microsoft.com, then menu → Apps → Install this site as an app.

Claude desktop — PWA

No official Linux app. Open https://claude.ai in Edge (or any Chromium browser) and use Install this site as an app the same way.

Proton-GE

Already handled by Bazzite: use the preinstalled ProtonUp-Qt GUI (or browse ujust — run ujust with no arguments to list recipes). Don't install anything extra.

Node / toolchains — not in the image

Node, npm, etc. are deliberately not layered. Use per-project versions instead:

brew install mise         # Homebrew ships in the base image
mise use node@22          # per-project .mise.toml; `mise use -g node@22` for a global default

(Plain brew install node also works if you just want one global Node.)

Display note

The 49" 32:9 (5120x1440) ultrawide needs nothing at the image layer. Post-install: set scale and refresh rate in KDE System Settings → Display; KDE's window tiling (Meta+drag, or a tiler like Polonium) is worth setting up at this width. VMs are remote via Remmina — there is intentionally no local hypervisor tooling in this image.

Maintenance

• Change the Flatpak list / packages: edit recipes/recipe.yml, push, and the next update picks it up. (Removing an app from the list does not uninstall it from the machine; flatpak uninstall it once by hand.)
• Jump Fedora majors: change image-version: stable-44 → stable-45 in the recipe when ready, push, then update normally.
• Check build status: the Actions tab; builds also run nightly, so a broken base shows up there before it reaches the machine.