steamify-cachyos/TECHNICAL.md

Technical details

How Steamify CachyOS works under the hood. For using it, see README.md; for problems, TROUBLESHOOTING.md.

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.

KDE wallet. KDE normally unlocks your wallet with the password you log in with; with autologin nobody types it, so apps that keep passwords in it (Brave, for example) ask for the wallet password. Single user mode does what SteamOS does: it uses Valve's empty wallet without a password (from steamdeck-kde-presets, checksum verified). Your own wallet in ~/.local/share/kwalletd/ is moved to kdewallet.kwl.bak-steamify (and .salt). Turning single user mode off puts it back, unchanged; the single user wallet, with anything saved in it meanwhile, is kept as kdewallet.kwl.steamify-single-user and used again the next time it's on. Passwords aren't shared between the two wallets.

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.

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 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

Installs CachyOS's cachyos-vapor package (the SteamOS Vapor theme the CachyOS handheld edition uses) from the CachyOS repository and switches your desktop to its Vapor global theme, including its desktop and window layout (like ticking "Desktop and window layout" in System Settings): Vapor colors and Plasma style, the SteamOS panel and launcher icon, and the Steam Deck wallpaper. Run it from the Plasma desktop: applying the layout needs a running Plasma session.

It also adds the SteamOS desktop extras that cachyos-vapor doesn't ship, taken from the newest steamdeck-kde-presets on Valve's SteamOS mirror (checksum verified) and installed to /usr/local:

• Add to Steam in the right-click menu of apps, AppImages and .exe files, and in the launcher: adds them to Steam as non-Steam games;
• Nested Desktop: add it to Steam from the launcher, then start it in gaming mode for a Plasma desktop inside gaming mode;
• the SteamOS Return to Gaming Mode icon (Steam logo with a return arrow);
• a window rule that keeps the Steam keyboard above other windows.

Turning it off restores your previous look and panel layout, and removes cachyos-vapor again if the wizard installed it (and nothing else, like cachyos-handheld, needs it).

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 every installed kernel (so the LTS kernel works too), 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;
• console-like power button: it puts the machine to sleep, and it never suspends by itself on mains power (the launcher's Shut Down still shuts down);
• installs and enables steamos-manager, the service Steam in gaming mode uses for hardware settings (fan, performance, and the HDMI-CEC settings when HDMI-CEC is on); 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 (uname -r) instead of the kernel DKMS builds for, so the wizard adds a DKMS override (/etc/dkms/leds-valve-dkms.conf) that passes DKMS's target kernel in. With it, DKMS rebuilds the driver whenever a kernel or its headers are installed or upgraded. A newly added kernel doesn't come with its headers, so ensure-kernel-headers.service checks at every boot and installs any missing -headers package, which makes DKMS build the driver for it.

HDMI-CEC

The HDMI-CEC item (on every PC; ticked by default only on a Steam Machine) installs Valve's CEC stack from its SteamOS holo repository, the newest holo-X.Y on steamdeck-packages.steamos.cloud, each package checked against the SHA-256 in Valve's package index:

• cecd, Valve's CEC daemon (a user service started with the desktop and gaming mode): TV remote keys become normal key presses (arrows, Enter, Back), and it turns the TV on and off with the PC;
• cec-audio-control: volume of the TV or receiver;
• inputattach-cec-units (with linuxconsole from CachyOS for inputattach): attaches USB CEC adapters (Pulse-Eight, RainShadow).

It works with any /dev/cec*: a GPU that has CEC on its HDMI port (the Steam Machine; the CachyOS kernel has DisplayPort CEC built in) or a USB adapter (CEC.md lists which PCs have one). The menu lists the CEC devices found. Also turn on CEC on the TV (Sony: BRAVIA Sync, Samsung: Anynet+, LG: SimpLink). On a Steam Machine steamos-manager writes cecd's settings from Steam's (wake the TV, put it to sleep), in ~/.config/cecd/config.d/, and Steam shows its HDMI-CEC settings; the wizard restarts steamos-manager so that happens right away. CachyOS's gaming mode script (/usr/lib/steamos/gamescope-session) sets STEAM_ENABLE_CEC=0, which hides those settings; Steam reads the script's variables from $XDG_RUNTIME_DIR/gamescope-environment. HDMI-CEC adds a drop-in for steam-launcher.service (/etc/systemd/user/steam-launcher.service.d/10-steamify-cec.conf) with a second EnvironmentFile= (/etc/steamify/steam-cec.env, STEAM_ENABLE_CEC=1), which overrides it from the next gaming mode start.

It's experimental: on SteamOS itself CEC can wake the Steam Machine right after it goes to sleep (Samsung TVs, SteamOS#2626) and upset CEC for the TV's other devices (SteamOS#2817). Turning it off removes the packages again (linuxconsole only if the wizard installed it).

Power-off fix (Steam Machine)

With recent kernels a Steam Machine starts again right after powering off: the newer 6.x, 7.0 and 7.1 updates and 7.2 (and probably every kernel after it). Linux stopped clearing the S4/S5 wake bits at probe (pinctrl-amd: Don't clear S4 wake bits at probe, in 7.2 and backported to stable kernels), and the firmware leaves that bit set on GPIO pin 18 (_SB.PCI0.GPP6). Valve's own kernel (linux-neptune-72) clears it at probe on Fremont, in a patch marked not for upstream ("until the firmware is fixed"), so CachyOS and mainline won't get it.

The Power-off fix sub-option of Steam Machine support (ticked along with it, can be unticked) builds a small module with DKMS for every installed kernel, steamify-fremont-poweroff (source in patches/steamify-fremont-poweroff.c). It only loads on Fremont (DMI board name) and touches one register: right before power-off (a SYS_OFF_MODE_POWER_OFF_PREPARE handler, after the drivers have shut down) it clears that pin's S4/S5 wake bit. On a kernel that already clears it, it does nothing. It logs the pin's state at load: dmesg | grep 'GPIO 18'; /sys/kernel/debug/gpio shows the S4/S5 column. Tested on a Steam Machine with linux-cachyos-bore 7.2.8: it stayed off three times in a row, and rebooted right away with the module unloaded.

Where Steam Machine support was set up before 2.2.0, the menu ticks the power-off fix as a new default sub-option (see feature versions below), so a normal run adds it.

Feature versions (updates)

Each component has a feature version (FEATURE_VERSION in lib/menu.sh): the Steamify version in which what it sets up last changed (2.1.0 for everything that hasn't changed since). After a component is turned on successfully, that version is recorded in ~/.local/state/cachyos-gamescope-boot/features.state (turning it off records off). Whether a component is on is always checked on the system itself; the version only decides about updates:

• On, recorded version older than the current one: ticked and re-applied by a normal run; the plan (and the app's review) says "update". A setup from before versions were recorded counts as 2.1.0, so on a machine set up with 2.1.0, Steam Machine support (2.2.0) is updated.
• A new default sub-option (not in NO_PRESELECT) whose parent is on and that was never turned on or off: ticked, so a normal run adds it. Turning it off once records off, so it isn't ticked again.

Set a component's entry to the new VERSION whenever what its <id>_enable sets up changes.

BIOS updates (Steam Machine)

The Update BIOS item is only shown on a Steam Machine and is never ticked by default. It shows the BIOS version you have now and the newest one Valve ships (the .cab file in its fremont-hw-support package, looked up on Valve's SteamOS mirror):

 [ ] Update BIOS: now F7F0107, newest F7F0108 (own risk)  (opt-in, runs once)

It can only be ticked when Valve has a newer BIOS than yours; when you're up to date, when the newest version can't be looked up (offline), or when an update is already waiting for a restart, it's greyed out.

When you run it, the wizard:

1. downloads Valve's package and checks its SHA-256 against Valve's repository, so it's exactly Valve's file;
2. asks fwupd whether the firmware is for this very machine (fwupd compares the firmware's hardware IDs with the device) and stops if it isn't;
3. shows a large red warning with the current and the new version, and asks whether you understand the risks (default: no);
4. shows the warning again and only continues when you type UPDATE;
5. hands the firmware to fwupd, which writes it during the next restart: choose "restart now" or restart later yourself.

At your own risk: a failed or interrupted BIOS update can leave the machine unable to start. Keep it on mains power, and never turn off the power, unplug it or press the power button while it updates, including during the restart; the screen can stay black for several minutes.

To walk through it without flashing anything, run the wizard with WIZARD_BIOS_DRY_RUN=1: it downloads and checks the package and shows both warnings, skips fwupd's device check, and only prints the install command.

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 - see TROUBLESHOOTING.md for the way out.

Project layout

File	Responsibility
steamify.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/boot-session.sh	Boot into gamescope or the desktop (steamify-boot-desktop.service)
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: installs and switches to cachyos-vapor
lib/steamos-extras.sh	SteamOS desktop extras from Valve's package (Add to Steam, Nested Desktop, icon, keyboard rule, KWallet)
lib/single-user.sh	Single user mode: no lock screen, user switching or log out
lib/wizard-shortcut.sh	Steamify shortcut: desktop icon and launcher entry that run the newest release
lib/bios.sh	Update BIOS (Steam Machine, opt-in): current/newest version, double confirmation, fwupd
lib/cec.sh	HDMI-CEC: Valve's cecd and friends from its holo repository
lib/steam-machine.sh	Steam Machine support: LED driver, LED access, steamos-manager
lib/fremont-poweroff.sh	Steam Machine support: the power-off fix (DKMS module from patches/)
patches/	Module sources and patches the scripts build or apply (patch_file); see its README
.github/tools/bundle.sh	Builds the single-file version (dist/steamify.sh), with patches/ embedded
.github/workflows/bundle.yml	Builds and checks it on every push; publishes it on main

The single-file version is generated: on every push to main, GitHub Actions runs .github/tools/bundle.sh, checks the result with bash -n and shellcheck, and publishes it as a release per version (tag v<VERSION>, never overwritten; the newest is marked latest, and the latest tag follows it). It inlines lib/*.sh and wraps the entry point in main(), so bash has read the whole file before anything runs; when stdin is a pipe (curl | bash) it reattaches the terminal for the menu (set WIZARD_KEEP_STDIN=1 to keep piped input).

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