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

The wizard is a menu: pick what you want, and it turns each part on or off. Everything you turn off is put back the way it was.

SteamOS conversion - boots straight into gaming mode, Switch to Desktop in Steam works and so does going back (the Return to Gaming Mode icon on the desktop), you're back in gaming mode after a restart, and Steam's on-screen keyboard (Steam + X) also works on the desktop.
SteamOS theme - Valve's own Vapor look for the desktop: wallpaper, dark mode and the SteamOS taskbar.
Steam Deck/Machine icons - Steam Deck button icons in gaming mode.
Single user mode - like SteamOS: never a login or lock screen, no user switching or logging out. Typing a password with a controller is no fun. (Needs 1.)
Steam Machine support - only shown on a Valve Steam Machine: the driver for the front LED bar, and the hardware settings in Steam (fan, TV control over HDMI-CEC).

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. You'll see a checklist:

   [x] SteamOS conversion: boot into gaming mode, Steam on the desktop  (now: off)
 > [x] Install SteamOS theme: Vapor look, dark mode, SteamOS taskbar  (now: off)
   [x] Install Steam Deck/Machine icons: Deck button icons in gaming mode  (now: off)
   [x] Single user mode: no password, lock screen or log out (SDDM)  (now: off)

  Up/Down move   Space select   Enter run   a run + re-apply what's on   q quit

Move with the arrow keys, tick or untick with Space, and press Enter to run. "now:" shows what's on at the moment. The wizard then shows what it will change, asks your password once, and at the end offers to restart (needed for changes to how the PC starts).

Run it again whenever you like - to change your choices, to turn things off again, or after a CachyOS update (press a in the menu to re-apply everything that's on).

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

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're not using single user mode).
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 something: run the wizard again and untick it.

Technical details

How turning things on and off works

At startup every component checks whether it is on (*_status in lib/). You choose; the wizard then turns off what you unticked (in reverse order) and turns on what you ticked. To be able to undo:

System files are backed up once, next to the original, with a .bak-gamescope-wizard suffix, and restored when you turn the component off.
KDE settings in your home directory are recorded with their previous value the first time the wizard changes them, in an undo journal under ~/.local/state/cachyos-gamescope-boot/. Turning the component off writes the old values back (or removes keys that didn't exist before). Setups made by older versions of the script, without a journal, fall back to KDE's defaults.
Packages installed for the conversion (Steam, gamescope-session, ...) are kept when you turn it off; Steam Machine support removes its own.

Single user mode: SDDM, no locking

Turning it on switches to SDDM and turns off everything that asks for a password or another user, per user: 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.) Turning it off restores all of that and moves the conversion back to plasma-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 (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.

Without single user mode, the conversion uses plasma-login-manager (CachyOS's default since March 2026), which needs the workarounds below.

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:

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.
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.)
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 each component changes

SteamOS conversion (lib/login-manager.sh, lib/steam-desktop.sh, lib/desktop-shortcut.sh):

installs missing packages: gamescope-session-cachyos, steam, mangohud, xterm, ttf-liberation, wqy-zenhei, plasma-keyboard;
SDDM (single user mode): 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, removes stray zzz-steamos-autologin*.conf files from manual troubleshooting (never zz-steamos-autologin.conf, which CachyOS's tools own), and installs /usr/local/bin/sync-steamos-session.sh plus sync-steamos-session.path/.service;
KWIN_IM_SHOW_ALWAYS=1 for the virtual keyboard and a steam-desktop-autostart systemd user service that starts Steam silently in Plasma only;
the Return to Gaming Mode shortcut; on plasma-login-manager with a narrow sudoers rule (/etc/sudoers.d/gamescope-session-switch) so it can restart the login manager without a password prompt.

Turning it off restores /etc/plasmalogin.conf from its backup, removes the SDDM autologin, sync bridge, shortcut, sudoers rule and Steam autostart, and switches back to plasma-login-manager.

Steam Deck/Machine icons: STEAM_GAMEPADUI_ARGS="-gamepadui -steamos3" in ~/.config/environment.d/ (and gamescope-session's own environment file), which makes Steam show Steam Deck button glyphs in gaming mode.

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 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)

The Steam Machine support component, only shown on Fremont hardware (DMI Valve/Fremont, or OEM/F7F on early units):

installs an AUR helper (yay) if neither yay nor paru is present;
installs the kernel headers for every installed kernel;
installs leds-valve-dkms-git from the AUR - Valve's own driver from the SteamOS kernel - builds it for the running kernel, and loads it at every boot (/etc/modules-load.d/leds-valve.conf);
adds a udev rule (/etc/udev/rules.d/70-valve-leds-user.rules) that gives your user the LED files, so Steam, which runs as you, can drive the bar;
installs and enables steamos-manager, the service Steam in gaming mode uses for hardware settings (fan, HDMI-CEC, performance); it recognises the Steam Machine from its DMI data.

Turning it off removes all of that again (the AUR helper is kept).

The LEDs appear as /sys/class/leds/valve-leds*. The driver's Makefile builds against the running kernel, so after a kernel update, boot the new kernel and re-apply (a in the menu) or run sudo dkms install leds-valve-dkms/0.1 -k "$(uname -r)".

Troubleshooting:

dkms status
ls -l /sys/class/leds/valve-leds*/
sudo dmesg | grep -i valve
cat /var/lib/dkms/leds-valve-dkms/0.1/build/make.log
journalctl --user -b | grep -i led

BIOS updates are not part of the wizard. Valve ships the Steam Machine BIOS as F7F0108.cab in its fremont-hw-support package for fwupd. To install it by hand (keep the machine on mains power and don't interrupt it):

sudo dmidecode -s bios-version     # current version
sudo pacman -S fwupd
curl -LO https://steamdeck-packages.steamos.cloud/archlinux-mirror/holo-3.9/os/x86_64/fremont-hw-support-20260807.1-1-any.pkg.tar.zst
mkdir fhw && tar -I zstd -xf fremont-hw-support-*.pkg.tar.zst -C fhw
sudo fwupdmgr install fhw/usr/share/fwupd/remotes.d/fremont/firmware/F7F0108.cab

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

Run the wizard and untick everything. Afterwards the PC boots to the normal CachyOS login screen again; packages installed for the conversion (Steam, gamescope-session, ...) stay installed.

Project layout

File	Responsibility
`setup-gamescope-boot.sh`	Entry point: checks, menu, apply, summary, restart
`lib/menu.sh`	The menu: detect, toggle, plan and apply changes
`lib/state.sh`	Undo journal for KDE settings (`kset`/`krevert`)
`lib/common.sh`	Output helpers, prompts, backups, plasmashell handling
`lib/packages.sh`	Required packages, AUR helper (yay/paru)
`lib/login-manager.sh`	SteamOS conversion: SDDM or plasmalogin autologin, sync bridge
`lib/steam-desktop.sh`	Steam in the Plasma session; Steam Deck/Machine icons
`lib/desktop-shortcut.sh`	Return to Gaming Mode shortcut and its sudoers rule
`lib/vapor-theme.sh`	SteamOS theme: Vapor, Valve's defaults, panel, dark mode
`lib/single-user.sh`	Single user mode: no lock screen, user switching or log out
`lib/steam-machine.sh`	Steam Machine support: LED driver, LED access, steamos-manager

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.

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

License

MIT - do whatever you want with it.

README.md

CachyOS Gamescope Boot Wizard