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Gaming Mode installer for KDE Plasma on CachyOS/Arch — switch between desktop and Steam Big Picture with Super+Alt+S
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28allday 218c72037c Fix Proton-GE install path breaking first Steam launch (v13.0-KDE) 
install_proton_ge_from_github() was creating ~/.steam/steam/compatibilitytools.d
via mkdir -p before Steam had ever been launched. That forces ~/.steam/steam
to exist as a real directory — which then prevents Steam, on first launch,
from creating it as a symlink to ~/.local/share/Steam. Result: desktop Steam
fails with "can't configure Steam data" / "Steam needs to be online to update".

Switch the install target to ~/.local/share/Steam/compatibilitytools.d/ (the
real Steam data dir). When Steam first runs it sets up ~/.steam/steam as a
symlink → ~/.local/share/Steam, so Proton-GE is picked up automatically.

Also check the legacy ~/.steam/steam/compatibilitytools.d path in the
idempotency probe so re-runs on previously-installed boxes don't redownload.

Bump version 12.27-KDE → 13.0-KDE (covers this fix plus the 2026-05-16
plasma-login-manager / AUR-reliability update which never bumped the string).
2026-05-17 18:25:39 +01:00
LICENSE Initial release v12.27-KDE - Gaming Mode installer for KDE Plasma on Arch/CachyOS 2026-04-12 19:55:45 +01:00
README.md Add plasma-login-manager support + AUR/CachyOS reliability fixes 2026-05-16 18:59:22 +01:00
super-alt-s.sh Fix Proton-GE install path breaking first Steam launch (v13.0-KDE) 2026-05-17 18:25:39 +01:00

README.md

Super Alt S - Gaming Mode for KDE Plasma

Switch between KDE Plasma desktop and Steam Big Picture Gaming Mode with a keyboard shortcut. Built for Arch Linux and CachyOS.

Super+Alt+S to enter Gaming Mode. Super+Alt+R to return to desktop.

What's new (2026-05-16)

A round of CachyOS-compatibility and reliability work. No new shortcuts or user-visible flow changes, but several quiet footguns from the initial release are fixed.

  • plasma-login-manager support. CachyOS now ships plasmalogin by default instead of SDDM. The installer detects which DM is active and parameterises every session-switch script, sudoers entry, and config path accordingly. SDDM hosts behave exactly as before.
  • Proton-GE installed direct from GitHub instead of via the AUR's proton-ge-custom-bin, which had been silently failing. The new path is idempotent (skips if a GE-Proton* directory already exists) and SHA-verified.
  • AUR resilience. Both the gamescope-session install and the optional-AUR-deps phase now check AUR reachability up front and retry the install up to 3× with 15s backoff. Stops the old "silent skip" mode where a transient AUR outage left the gaming session uninstalled.
  • Fixed: CachyOS package conflicts. gamescope-session-cachyos (which Provides= the -git names but is missing files gamescope-session-plus needs) is now removed pre-emptively, then locked in IgnorePkg so pacman -Syu won't try to swap it back. Resolves the autologin black-screen loop a few users hit.
  • Fixed: SDDM drop-in priority. Renamed /etc/sddm.conf.d/zz-gaming-session.conf → zzz-gaming-session.conf so it outranks CachyOS's own zz-steamos-autologin.conf (lexical sort). The old file is auto-removed during install.
  • Fixed: Limine on CachyOS. When /etc/default/limine + limine-update are present, kernel-param edits go there (the source of truth) rather than to /boot/limine.conf, which gets regenerated on every mkinitcpio run.
  • Post-install verification now hard-fails with a clear remediation message if gamescope-session-plus is missing after the AUR build, instead of letting you reboot into a broken session.
  • Removed CFS sysctls from the sudoers entries (sched_migration_cost_ns, sched_min_granularity_ns, sched_latency_ns) — these knobs were deleted from the kernel when EEVDF replaced CFS in 6.6, so the sudoers lines just produced errors.

What it does

This installer sets up a full console-like gaming experience on your KDE Plasma desktop by configuring:

  • Gamescope session using ChimeraOS packages (gamescope-session-git, gamescope-session-steam-git)
  • Steam Big Picture running in a dedicated Wayland session via gamescope
  • One-key switching between KDE Plasma and Gaming Mode — works with SDDM or plasma-login-manager (auto-detected)
  • GPU auto-detection for NVIDIA, AMD dGPU, and AMD APU systems
  • Performance mode with CPU governor, GPU power management, and kernel tuning
  • NetworkManager integration so Steam has network access even if your desktop uses iwd/systemd-networkd
  • External drive auto-mounting for Steam libraries on secondary drives
  • Shader cache optimisation for reduced stuttering
  • Installation verification to confirm everything is set up correctly

Requirements

  • Arch Linux or CachyOS (or any Arch-based distro with KDE Plasma)
  • KDE Plasma 6 (Wayland)
  • SDDM or plasma-login-manager display manager (CachyOS ships plasmalogin by default — the installer auto-detects either)
  • AMD or NVIDIA GPU (Intel-only is not supported)
  • Steam (installed during setup if missing)
  • AUR helper (yay or paru) for ChimeraOS session packages

Install

git clone https://git.no-signal.uk/nosignal/super-alt-s.git
cd super-alt-s
chmod +x super-alt-s.sh
./super-alt-s.sh

The installer is interactive and will walk you through each step, asking before making changes.

Usage

Action Shortcut
Enter Gaming Mode Super+Alt+S (from KDE Plasma)
Return to Desktop Super+Alt+R (from Gaming Mode)
Return to Desktop (fallback) Steam > Power > Exit to Desktop

What gets installed

Packages (via pacman + AUR)

  • Steam and all required 32-bit libraries
  • GPU-specific Vulkan drivers (NVIDIA or AMD)
  • gamescope, mangohud, gamemode
  • Proton-GE — latest release pulled direct from GitHub into ~/.steam/steam/compatibilitytools.d/ (the AUR proton-ge-custom-bin is unreliable, so we skip it)
  • gamescope-session-git + gamescope-session-steam-git (ChimeraOS AUR packages, with retry-on-failure + AUR reachability checks)
  • python-evdev (for keybind monitoring)

Scripts

File Purpose
/usr/local/bin/switch-to-gaming Switches from KDE to Gaming Mode
/usr/local/bin/switch-to-desktop Switches from Gaming Mode to KDE
/usr/local/bin/gamescope-session-nm-wrapper Session wrapper with NetworkManager + performance mode
/usr/local/bin/gaming-keybind-monitor Python daemon monitoring Super+Alt+R in Gaming Mode
/usr/local/bin/gaming-session-switch Updates SDDM config for session switching
/usr/local/bin/gamescope-nm-start Starts NetworkManager for gaming session
/usr/local/bin/gamescope-nm-stop Stops NetworkManager and restores iwd
/usr/local/bin/steam-library-mount Auto-mounts external drives with Steam libraries
/usr/lib/os-session-select Handles Steam's "Exit to Desktop" menu option

System config

File Purpose
/etc/sddm.conf.d/zzz-gaming-session.conf (or /etc/plasma-login-manager.conf.d/) DM autologin session switching — zzz-* prefix outranks CachyOS's own zz-steamos-autologin.conf
/etc/sudoers.d/gaming-session-switch Passwordless sudo for session switching
/etc/sudoers.d/gaming-mode-sysctl Passwordless sudo for performance tuning
/etc/udev/rules.d/99-gaming-performance.rules CPU/GPU sysfs permissions
/etc/security/limits.d/99-gaming-memlock.conf Memory lock limits for esync
/etc/pipewire/pipewire.conf.d/10-gaming-latency.conf Low-latency audio
/etc/environment.d/99-shader-cache.conf Shader cache sizes
/etc/polkit-1/rules.d/50-gamescope-networkmanager.rules NM access for wheel group
/etc/polkit-1/rules.d/50-udisks-gaming.rules Drive mount access for wheel group

User config

File Purpose
~/.config/environment.d/gamescope-session-plus.conf Resolution, refresh rate, GPU settings
~/.config/kglobalshortcutsrc Super+Alt+S shortcut registration

GPU support

NVIDIA

  • Auto-detects NVIDIA GPU and installs required drivers/utils
  • Checks and configures nvidia-drm.modeset=1 kernel parameter (supports GRUB, systemd-boot, and Limine)
  • Sets up GBM backend and Vulkan adapter
  • NVIDIA gamescope wrapper with --force-composition if supported
  • Caps resolution at 2560x1440 for gamescope compatibility
  • Performance mode includes persistence mode, max power limit, and runtime suspend disable

AMD (dGPU)

  • Installs Vulkan RADEON drivers
  • Enables adaptive sync and HDR
  • Distinguishes between discrete GPUs and integrated APUs using PCI device identification

AMD APU

  • Supported as a fallback when no discrete GPU is found
  • Same session setup with APU-specific display detection

Verify installation

Run verification without reinstalling:

./super-alt-s.sh --verify

This checks all files, permissions, packages, user groups, and service status.

Options

./super-alt-s.sh              # Full install
./super-alt-s.sh --verify     # Verification only
./super-alt-s.sh --version    # Show version
./super-alt-s.sh --help       # Show help

How it works

  1. KDE to Gaming Mode (Super+Alt+S): The switch-to-gaming script updates the display manager's session config to gamescope-session-steam-nm, kills any existing gamescope, and restarts the DM service. The DM auto-logs in to the gaming session. (SDDM and plasma-login-manager are both supported — the installer detects which one you're running and parameterises the scripts accordingly.)

  2. Gaming session startup: The gamescope-session-nm-wrapper enables performance mode (CPU governor, GPU power), starts NetworkManager, launches the Steam library drive monitor, starts the keybind monitor, then hands off to ChimeraOS's gamescope-session-plus which launches gamescope with Steam.

  3. Gaming Mode to KDE (Super+Alt+R): The gaming-keybind-monitor Python daemon detects the key combo via evdev and calls switch-to-desktop, which shuts down Steam, kills gamescope, updates the DM config back to KDE Plasma, and restarts the DM service.

  4. Cleanup on exit: Performance mode is restored to balanced, NetworkManager is stopped (iwd restarted if needed), drive monitor and keybind monitor are killed.

Troubleshooting

No network in Gaming Mode

  • Check NetworkManager is installed: pacman -S networkmanager
  • Test manually: sudo systemctl start NetworkManager && nmcli general
  • Check logs: journalctl -u NetworkManager -n 50

Shortcut not working in KDE

  • Log out and back in after install
  • Or set manually: System Settings > Shortcuts > search "Gaming Mode"

Super+Alt+R not working in Gaming Mode

  • Ensure you're in the input group: groups | grep input
  • Check python-evdev: python3 -c "import evdev"
  • Check input devices: ls /dev/input/event*

NVIDIA: black screen or no display

  • Verify kernel parameter: cat /proc/cmdline | grep nvidia-drm.modeset
  • Reboot if you just added the parameter
  • Check DRM cards: ls /sys/class/drm/card*/device/driver -la

Proton-GE not appearing in Steam

  • Check it installed: ls ~/.steam/steam/compatibilitytools.d/
  • Restart Steam fully (not just the window — quit from the tray) so it picks up new compat tools
  • Re-run the installer to retry the GitHub download if the directory is empty

Black screen / login loop after entering Gaming Mode (CachyOS)

  • Usually means gamescope-session-cachyos was reinstalled by a system update. Re-run ./super-alt-s.sh to remove it and lock it in IgnorePkg.
  • Confirm the AUR build succeeded: ls /usr/share/gamescope-session-plus/gamescope-session-plus

License

MIT