CachyOS Gamescope Boot Wizard

Turn a CachyOS desktop PC into a SteamOS-style console: it boots straight into Steam's Big Picture (gamescope), and you can switch to the KDE Plasma desktop and back whenever you like - just like on a Steam Deck or Valve's Steam Machine.

Out of the box, CachyOS doesn't quite manage this: the switch to the desktop can hang, and the PC doesn't reliably boot back into gaming mode. This script fixes that and sets everything up for you.

What you get

• Boots into gaming mode automatically - you never see a login screen, just like SteamOS.
• Switch to Desktop from Steam's power menu works, and so does going back: use the Return to Gaming Mode icon on the desktop, or just log out.
• Back to gaming mode after a restart, like SteamOS.
• Steam's on-screen keyboard (Steam + X) also works on the desktop.
• Optional: the SteamOS desktop look - Valve's own Vapor theme, wallpaper, dark mode and taskbar.
• Optional, Steam Machine only: a driver for the front LED bar.

Requirements

• CachyOS with the KDE Plasma desktop (the default CachyOS Desktop edition)
• Your normal user account, with permission to use sudo

Installation

Open Konsole on your Plasma desktop and run:

git clone <this-repo-url>
cd <this-repo>
./setup-gamescope-boot.sh

Run it as yourself, not as root. It asks for your password once, then asks a few yes/no questions:

• Single user, no password, like SteamOS? Recommended for a console. You never see a login or lock screen, and there's no user switching or logging out - typing a password with a controller is no fun. This switches to SDDM, the login manager SteamOS uses. Say no to keep CachyOS's default login manager and KDE's normal lock screen; gaming mode still starts automatically.
• whether to install missing packages;
• the LED driver (Steam Machine only) and the SteamOS look.

At the end it offers to restart. The switch to SDDM takes effect from that restart.

Keep the whole folder: the script needs the files in lib/ next to it.

It's safe to run again later, for example after a CachyOS update.

Using it

• To the desktop: in gaming mode, open the Steam menu and choose Power > Switch to Desktop.
• Back to gaming mode: double-click Return to Gaming Mode on the desktop (or log out, if you didn't choose single user).
• After a restart you always start in gaming mode.

Prefer to decide yourself where your PC starts? Run one of these in Konsole:

steamos-session-select persistent  # start where you left off last time
steamos-session-select oneshot     # always start in gaming mode (default)

If something goes wrong

Gaming mode shows a black screen or keeps restarting. Press Ctrl+Alt+F3, log in with your username and password, and run:

sudo /usr/lib/steamos/steam-set-session plasma.desktop && sudo systemctl restart display-manager

That takes you back to the desktop.

The LED bar on the Steam Machine stays dark. Restart the PC once more; a freshly installed driver often needs a reboot. Still dark? See Front LED bar under technical details.

Undo the SteamOS look: pick another theme under System Settings > Colors & Themes > Global Theme.

To remove everything the script set up, see Removing everything.

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Technical details

Single user: SDDM, no locking

The wizard's first question. Answering yes switches to SDDM and turns off everything that asks for a password or another user, per user and without touching system files: action/lock_screen, switch_user and start_new_session restrictions in kdeglobals, no automatic locking (kscreenlockerrc), Meta+L and Ctrl+Alt+Del unbound, and the launcher shows only Sleep / Restart / Shut Down (kickoff primaryActions=3), which hides the Session dropdown with Log Out. (Restricting action/logout would also hide Restart and Shut Down.) Answering no restores KDE's defaults and keeps the current login manager.

SDDM is what SteamOS uses, and CachyOS's steam-set-session supports it directly: it writes /etc/sddm.conf.d/zz-steamos-autologin.conf, which SDDM honours. The script installs and enables sddm (disabling the current display manager, active from the next boot), writes User=, Session= and Relogin=true to /etc/sddm.conf.d/10-gamescope-autologin.conf, and removes any [Autologin] from /etc/sddm.conf (read last, so it would override both). No sync bridge or sudoers rule is needed; the shortcut just runs steamos-session-select gamescope, which logs out, and Relogin=true logs straight back in to gamescope. Switching an existing plasma-login-manager setup to SDDM removes the sync bridge.

Keeping plasma-login-manager (CachyOS's default since March 2026) needs the workarounds below.

Why this is needed (plasma-login-manager)

CachyOS's gamescope-session-cachyos package ships steamos-session-select, which is meant to work exactly like it does on real SteamOS. Since the March 2026 release, CachyOS uses plasma-login-manager instead of SDDM, and three things get in the way:

1. No User= written to the autologin config. steam-set-session (called by steamos-session-select) only writes a Session= key. plasma-login-manager needs both Session= and User= to autologin at all; without User= it shows the greeter every boot.

2. Missing /etc/plasmalogin.conf.d directory. Without it, steam-set-session fails, and Steam's "Switch to Desktop" hangs forever. (Fixed upstream in gamescope-session-cachyos 1.1.6; the script still creates the directory for older versions.)

3. The base /etc/plasmalogin.conf wins over conf.d, and CachyOS ships it with Session=plasma. Every tool that changes sessions (steamos-session-select, Steam's power menu, and cachyos-gamescope-autologin.service, which resets you to gamescope after a desktop session) only writes /etc/plasmalogin.conf.d/zz-steamos-autologin.conf. The base file takes priority, so none of those switches stick.

The script sets Session=, User= and Relogin=true in the base config, and installs a small systemd path watcher that copies whatever CachyOS's tools write to the conf.d fragment into the base config.

What the script changes

In order:

1. Checks that it runs as the user that should autologin, and asks whether to switch to SDDM (see above).
2. Installs missing packages: gamescope-session-cachyos, steam, mangohud, xterm, ttf-liberation, wqy-zenhei, plasma-keyboard.
3. SDDM: installs/enables SDDM and writes its autologin config. plasma-login-manager: creates /etc/plasmalogin.conf.d, backs up and rewrites the [Autologin] section of /etc/plasmalogin.conf, and removes stray zzz-steamos-autologin*.conf files from manual troubleshooting (never zz-steamos-autologin.conf, which CachyOS's tools own).
4. plasma-login-manager only: installs /usr/local/bin/sync-steamos-session.sh plus sync-steamos-session.path/.service, which keep the base config in sync with session switches.
5. Sets up Steam for the desktop: STEAM_GAMEPADUI_ARGS="-gamepadui -steamos3" (gamepad UI with Steam Deck glyphs), KWIN_IM_SHOW_ALWAYS=1 for the virtual keyboard, and a steam-desktop-autostart systemd user service that starts Steam silently in Plasma only.
6. (Steam Machine, optional) the LED driver - see below.
7. (Optional) the SteamOS desktop look - see below.
8. Creates the Return to Gaming Mode shortcut. On plasma-login-manager it also adds a narrow sudoers rule (/etc/sudoers.d/gamescope-session-switch) so it can restart the login manager without a password prompt.

Re-running doesn't duplicate any settings. Every system file it modifies is backed up once, next to the original, with a .bak-gamescope-wizard suffix.

SteamOS desktop look

Downloads Valve's official steamdeck-kde-presets package from Valve's SteamOS mirror and installs it into ~/.local/share - nothing system-wide:

• the Vapor global theme, color scheme, Plasma style, wallpapers and icons;
• the Vapor GTK theme, Konsole profile and user avatars;
• Valve's SteamOS desktop defaults, merged into your own config: Noto Sans fonts, no Xwayland input-permission prompt for Steam Input, the window rule that keeps the Steam keyboard on top and out of the taskbar, no screen locking, no welcome screen, light file indexing;
• the SteamOS panel: solid (not floating), full width, 44 px high, tray icons scaled to fit, date below the time, and the SteamOS launcher icon;
• dark mode for GTK, libadwaita and portal-aware apps (Firefox, Flatpaks).

Run inside a Plasma session, it applies everything live; otherwise it takes effect at the next desktop login.

Package version. The script always takes the newest steamdeck-kde-presets from the highest-numbered SteamOS release repository on the mirror (jupiter-3.9, jupiter-3.10, ...). That repository's pacman database gives the exact file name and SHA-256 checksum, which is verified after downloading. If the lookup fails, it falls back to the known-good 3.9.4 (see install_vapor_theme() in lib/vapor-theme.sh). To check the current version yourself:

m=https://steamdeck-packages.steamos.cloud/archlinux-mirror
r=$(curl -fsL $m/ | grep -oE 'jupiter-[0-9]+\.[0-9]+/' | tr -d / | sort -V | tail -n 1)
curl -fsL $m/$r/os/x86_64/$r.db | bsdtar -tf - | grep -o '^steamdeck-kde-presets-[^/]*' | sort -u

Front LED bar (Steam Machine)

Standard desktop kernels, including CachyOS's, lack Valve's leds-valve driver, so the Steam Machine's front LED bar goes dark or "breathes". On Fremont hardware (DMI Valve/Fremont) the script offers to:

• install an AUR helper (yay) if neither yay nor paru is present;
• install the kernel headers for every installed kernel;
• install leds-valve-dkms-git from the AUR, build it for the running kernel, and load it at every boot (/etc/modules-load.d/leds-valve.conf);
• optionally install the experimental openrgb-git, which can drive the bar.

The LEDs appear as /sys/class/leds/valve-leds*. Steam itself only drives the bar (e.g. download progress) in real SteamOS Game Mode.

The driver's Makefile builds against the running kernel, so after a kernel update, boot the new kernel and re-run the script (or sudo dkms install leds-valve-dkms/0.1 -k "$(uname -r)").

Troubleshooting:

dkms status
ls /sys/class/leds | grep valve
sudo dmesg | grep -i valve
cat /var/lib/dkms/leds-valve-dkms/0.1/build/make.log

Manual session control

steamos-session-select gamescope   # switch to gamescope right now
steamos-session-select plasma      # switch to desktop right now
steamos-session-select persistent  # remember the last-used session across reboots
steamos-session-select oneshot     # always start in gamescope (default, like a Deck)

With Relogin=true, a gamescope session that fails to start is restarted immediately, which can turn into a loop - hence the Ctrl+Alt+F3 escape above.

Removing everything

# SDDM: go back to plasma-login-manager
sudo rm /etc/sddm.conf.d/10-gamescope-autologin.conf
sudo systemctl disable sddm && sudo systemctl enable plasmalogin

# plasma-login-manager: restore the original login config
sudo cp /etc/plasmalogin.conf.bak-gamescope-wizard /etc/plasmalogin.conf

# session sync watcher
sudo systemctl disable --now sync-steamos-session.path
sudo rm /etc/systemd/system/sync-steamos-session.path
sudo rm /etc/systemd/system/sync-steamos-session.service
sudo rm /usr/local/bin/sync-steamos-session.sh
sudo systemctl daemon-reload

# shortcut and its sudoers rule
sudo rm /etc/sudoers.d/gamescope-session-switch
rm ~/Desktop/"Return to Gaming Mode.desktop"

# Steam desktop autostart and environment
systemctl --user disable --now steam-desktop-autostart.service
rm ~/.config/systemd/user/steam-desktop-autostart.service
rm ~/.config/environment.d/99-gamescope-steam-glyphs.conf \
   ~/.config/environment.d/99-kde-virtual-keyboard.conf

# LED driver (Steam Machine)
sudo rm /etc/modules-load.d/leds-valve.conf
sudo pacman -R leds-valve-dkms-git

Project layout

File	Responsibility
setup-gamescope-boot.sh	Entry point: user and sudo checks, step order, summary, reboot
lib/common.sh	Output helpers, yes/no prompts, backups
lib/packages.sh	Required packages, AUR helper (yay/paru)
lib/login-manager.sh	SDDM or plasmalogin choice and autologin, session sync bridge
lib/steam-desktop.sh	Steam in the Plasma session: gamepad UI flags, virtual keyboard, autostart
lib/led-driver.sh	Fremont detection, kernel headers, LED driver, OpenRGB
lib/vapor-theme.sh	Vapor theme, Valve's SteamOS defaults, panel, dark mode
lib/desktop-shortcut.sh	Return to Gaming Mode shortcut and its sudoers rule

Notes for contributors and AI coding agents are in AGENTS.md.

Caveats

• This works around CachyOS/plasma-login-manager behavior as of September 2026. If CachyOS fixes steam-set-session upstream, parts of this script become unnecessary - please open an issue or PR if you notice that.
• Tested on a Valve Steam Machine running CachyOS Desktop edition. It should work on any CachyOS desktop install using plasma-login-manager, but hasn't been tested on Steam Deck/Legion Go hardware.

Related upstream reports

• CachyOS/gamescope-session#9 - "Switch to Desktop" hang due to missing /etc/plasmalogin.conf.d

License

MIT - do whatever you want with it.