commit the script

README.md

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+# CachyOS Gamescope Boot Wizard
+
+A setup script that makes a CachyOS desktop install (running KDE Plasma +
+`plasma-login-manager`) always boot into a **Steam Deck-style gamescope
+session** — the same "always boots into Big Picture, switch to desktop and
+back on demand" experience SteamOS gives you on a real Deck or the Valve
+Steam Machine.
+
+It exists because, as of the CachyOS March 2026 release (which switched the
+default login manager from SDDM to `plasma-login-manager`), the stock
+`gamescope-session-cachyos` tooling has a few gaps that stop this from
+working out of the box. This script patches around them.
+
+## What's actually broken (and what this fixes)
+
+CachyOS's `gamescope-session-cachyos` package ships `steamos-session-select`,
+which is meant to work exactly like it does on real SteamOS. On a
+`plasma-login-manager` system, three things get in the way:
+
+1. **No `User=` written to the autologin config.**
+   `steam-set-session` (the script `steamos-session-select` calls under the
+   hood) only ever writes a `Session=` key to the autologin config file. On
+   SDDM this is fine, because SDDM's `User=` is set once by the installer and
+   never touched again. `plasma-login-manager` needs *both* `Session=` and
+   `User=` present to autologin at all — without `User=`, it just falls back
+   to showing the greeter every boot.
+
+2. **Missing `/etc/plasmalogin.conf.d` directory.**
+   If that directory doesn't exist, `steam-set-session` fails outright when
+   it tries to write to it. In practice this shows up as Steam's **"Switch to
+   Desktop"** hanging forever on a "Switching to Desktop" message with no way
+   back except a hard reset.
+
+3. **The base `/etc/plasmalogin.conf` wins over conf.d, and CachyOS ships it
+   hardcoded to `Session=plasma`.**
+   Every CachyOS tool that changes sessions (`steamos-session-select`, Steam's
+   power menu, and the `cachyos-gamescope-autologin.service` that's supposed
+   to reset you back to gamescope after a desktop session) only ever writes
+   to `/etc/plasmalogin.conf.d/zz-steamos-autologin.conf`. But the *base*
+   `/etc/plasmalogin.conf` file takes priority over that fragment, and it
+   ships with `Session=plasma` baked in — so none of those session switches
+   ever actually stick, no matter what the fragment says.
+
+This script fixes all three: it ensures the conf.d directory exists, sets the
+base config's `Session=`, `User=`, and `Relogin=true` correctly, and installs
+a small `systemd` path-watcher that keeps the base config in sync with
+whatever CachyOS's own tools write to the conf.d fragment — so switching
+sessions from inside Steam or the desktop actually works, in both
+directions, and resets to gamescope on the next boot by default (matching
+real Deck/SteamOS behavior).
+
+## Requirements
+
+- CachyOS (or an Arch-based system) with `pacman`
+- KDE Plasma installed
+- `plasma-login-manager` as the active display manager
+  *(the script will warn and ask for confirmation if it detects SDDM or
+  something else instead — most of these workarounds are specific to
+  `plasma-login-manager`)*
+- A regular user account with `sudo` access
+
+## Usage
+
+```bash
+git clone <this-repo-url>
+cd <this-repo>
+chmod +x setup-gamescope-boot.sh
+./setup-gamescope-boot.sh
+```
+
+Run it as your normal user, **not** as root — it calls `sudo` internally for
+the specific commands that need it.
+
+The script will:
+
+1. Ask which user account should autologin into gamescope (defaults to
+   whoever's running the script).
+2. Check for and offer to install `gamescope-session-cachyos`, `steam`, and
+   `mangohud` if any are missing.
+3. Create `/etc/plasmalogin.conf.d` if it doesn't exist.
+4. Back up and rewrite `/etc/plasmalogin.conf`'s `[Autologin]` section.
+5. Remove any stray manual override files from earlier troubleshooting
+   attempts (only files matching `zzz-steamos-autologin*.conf` — it never
+   touches `zz-steamos-autologin.conf`, which CachyOS's own tools own).
+6. Install a sync script (`/usr/local/bin/sync-steamos-session.sh`) and a
+   `systemd` path unit that keeps the base config aligned with session
+   switches made through Steam or `steamos-session-select`.
+7. Ask whether to reboot immediately to test it.
+
+It's **safe to re-run** — every step checks current state first, and any
+file it modifies gets backed up once with a `.bak-gamescope-wizard` suffix
+before the first change.
+
+## After running it
+
+Boot straight into gamescope: it should happen automatically. From inside
+gamescope, Steam's **Power → Switch to Desktop** should now work. From the
+desktop, logging out should drop you back into gamescope automatically
+(thanks to CachyOS's own `cachyos-gamescope-autologin.service`, which this
+script doesn't replace — it just makes sure the setting it writes actually
+takes effect).
+
+You can also switch sessions manually at any time:
+
+```bash
+steamos-session-select gamescope   # switch to gamescope right now
+steamos-session-select plasma      # switch to desktop right now
+steamos-session-select persistent  # remember whichever session you used last, across reboots
+steamos-session-select oneshot     # always start in gamescope regardless of what you used last (the default Deck-like behavior)
+```
+
+## Restoring the originals
+
+Every file the script modifies is backed up next to itself:
+
+```bash
+sudo cp /etc/plasmalogin.conf.bak-gamescope-wizard /etc/plasmalogin.conf
+```
+
+To fully remove the sync watcher this script adds:
+
+```bash
+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
+```
+
+## Caveats
+
+- This works around current CachyOS/`plasma-login-manager` behavior as of
+  September 2026. If CachyOS fixes `steam-set-session` upstream to write
+  `User=` and to target whichever base config the login manager actually
+  reads, this script becomes unnecessary — check for updates before running
+  it on a freshly reinstalled system.
+- Tested on a Valve Steam Machine (desktop AMD APU + discrete GPU) running
+  CachyOS Desktop edition. Should apply to any CachyOS desktop install using
+  `plasma-login-manager`, but hasn't been tested on Steam Deck/Legion Go
+  hardware, which typically ship with SDDM instead.
+- If you find CachyOS has patched the underlying issue, please open an issue
+  or PR here so the script can detect that and skip the workaround.
+
+## Related upstream reports
+
+- [CachyOS/gamescope-session#9](https://github.com/CachyOS/gamescope-session/issues/9) — "Switch to Desktop" hang due to missing `/etc/plasmalogin.conf.d`
+
+## License
+
+MIT — do whatever you want with it.

setup-gamescope-boot.sh

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+#!/bin/bash
+#
+# setup-gamescope-boot.sh
+#
+# Wizard to configure a CachyOS (KDE Plasma + plasma-login-manager) install
+# to always boot into a Steam Deck-style gamescope session, with the
+# ability to switch to Plasma desktop and back, Deck-style, and have it
+# reset to gamescope on the next boot/logout.
+#
+# Covers three real bugs found on CachyOS as of Sep 2026:
+#   1. steam-set-session never writes User= to plasmalogin's autologin
+#      config, so plasma-login-manager never actually autologs in.
+#   2. steam-set-session fails outright if /etc/plasmalogin.conf.d is
+#      missing, breaking "Switch to Desktop" from inside gamescope.
+#   3. /etc/plasmalogin.conf (the base config) hardcodes Session=plasma
+#      and takes priority over anything written to
+#      /etc/plasmalogin.conf.d/*.conf, so session switches never stick
+#      without a bridge that copies the conf.d value back into the base
+#      file, plus Relogin=true so ending a session re-triggers autologin
+#      instead of dropping to the greeter.
+#
+# Safe to re-run: it is idempotent and backs up files before editing.
+
+set -uo pipefail
+
+# ---------- helpers ----------
+
+c_reset="\033[0m"; c_bold="\033[1m"; c_green="\033[32m"; c_yellow="\033[33m"; c_red="\033[31m"; c_cyan="\033[36m"
+
+info()  { echo -e "${c_cyan}==>${c_reset} $*"; }
+ok()    { echo -e "${c_green}✔${c_reset} $*"; }
+warn()  { echo -e "${c_yellow}!${c_reset} $*"; }
+err()   { echo -e "${c_red}✘ $*${c_reset}" >&2; }
+ask_yn() {
+    local prompt="$1" default="${2:-y}" reply
+    local hint="[Y/n]"; [[ "$default" == "n" ]] && hint="[y/N]"
+    read -rp "$(echo -e "${c_bold}${prompt}${c_reset} ${hint} ")" reply
+    reply="${reply:-$default}"
+    [[ "$reply" =~ ^[Yy]$ ]]
+}
+
+require_root_helper() {
+    # Re-exec any privileged step through sudo rather than requiring the
+    # whole script to run as root, so $HOME/whoami stay correct for the
+    # target user detection below.
+    if [[ $EUID -eq 0 && -z "${SUDO_USER:-}" ]]; then
+        err "Please run this script as your normal user (it will call sudo itself), not directly as root."
+        exit 1
+    fi
+}
+
+backup_file() {
+    local f="$1"
+    if [[ -f "$f" && ! -f "${f}.bak-gamescope-wizard" ]]; then
+        sudo cp -a "$f" "${f}.bak-gamescope-wizard"
+        info "Backed up $f -> ${f}.bak-gamescope-wizard"
+    fi
+}
+
+# ---------- start ----------
+
+require_root_helper
+
+echo -e "${c_bold}CachyOS Steam Deck-style Gamescope Boot Wizard${c_reset}"
+echo "This sets your machine up to always boot into gamescope (like SteamOS),"
+echo "with working Switch-to-Desktop and switch-back, surviving reboots."
+echo
+
+if ! command -v pacman >/dev/null 2>&1; then
+    err "This doesn't look like an Arch/CachyOS system (no pacman found). Aborting."
+    exit 1
+fi
+
+TARGET_USER="${SUDO_USER:-$USER}"
+read -rp "$(echo -e "${c_bold}Which user should autologin into gamescope?${c_reset} [${TARGET_USER}] ")" input_user
+TARGET_USER="${input_user:-$TARGET_USER}"
+
+if ! id "$TARGET_USER" >/dev/null 2>&1; then
+    err "User '$TARGET_USER' does not exist on this system."
+    exit 1
+fi
+ok "Using user: $TARGET_USER"
+echo
+
+# ---------- 1. Login manager check ----------
+
+DM="$(systemctl show -p Id --value display-manager 2>/dev/null | sed 's/\.service$//')"
+info "Detected display manager: ${DM:-none}"
+
+if [[ "$DM" != "plasmalogin" ]]; then
+    warn "This wizard was built and tested against plasma-login-manager (plasmalogin)."
+    warn "Detected display manager is '${DM:-unknown}'. SDDM setups don't need"
+    warn "most of these workarounds (SDDM's own Autologin works out of the box);"
+    warn "this script will still try, but review the output carefully."
+    ask_yn "Continue anyway?" n || exit 0
+fi
+echo
+
+# ---------- 2. Install packages ----------
+
+info "Checking required packages: gamescope-session-cachyos, steam, mangohud"
+MISSING=()
+for pkg in gamescope-session-cachyos steam mangohud; do
+    pacman -Qi "$pkg" >/dev/null 2>&1 || MISSING+=("$pkg")
+done
+
+if [[ ${#MISSING[@]} -gt 0 ]]; then
+    info "Missing packages: ${MISSING[*]}"
+    if ask_yn "Install them now?"; then
+        sudo pacman -S --needed "${MISSING[@]}"
+    else
+        err "Cannot continue without these packages."
+        exit 1
+    fi
+else
+    ok "All required packages already installed."
+fi
+echo
+
+# ---------- 3. Ensure plasmalogin.conf.d exists (fixes Switch-to-Desktop crash) ----------
+
+info "Ensuring /etc/plasmalogin.conf.d exists (fixes the 'Switching to Desktop' hang bug)"
+sudo mkdir -p /etc/plasmalogin.conf.d
+ok "Directory present."
+echo
+
+# ---------- 4. Fix the base /etc/plasmalogin.conf ----------
+#
+# steam-set-session only ever writes to /etc/plasmalogin.conf.d/*.conf,
+# but the base /etc/plasmalogin.conf takes priority and, as shipped by
+# CachyOS, hardcodes Session=plasma with no User= and no Relogin=. We
+# rewrite the [Autologin] block cleanly here.
+
+BASE_CONF="/etc/plasmalogin.conf"
+info "Configuring $BASE_CONF (Session=gamescope-session.desktop, User=$TARGET_USER, Relogin=true)"
+backup_file "$BASE_CONF"
+
+sudo touch "$BASE_CONF"
+
+# Strip any existing [Autologin] section (from the first [Autologin] line
+# to the next section header or EOF), then append a clean one. This is
+# safer than a series of seds for an unknown starting state.
+sudo awk '
+    BEGIN { in_autologin=0 }
+    /^\[Autologin\]/ { in_autologin=1; next }
+    /^\[/ { in_autologin=0 }
+    !in_autologin { print }
+' "$BASE_CONF" | sudo tee "${BASE_CONF}.tmp" > /dev/null
+
+sudo mv "${BASE_CONF}.tmp" "$BASE_CONF"
+
+sudo tee -a "$BASE_CONF" > /dev/null << EOF
+[Autologin]
+Session=gamescope-session.desktop
+User=$TARGET_USER
+Relogin=true
+EOF
+
+ok "Base autologin config written:"
+sudo sed -n '/\[Autologin\]/,/^\[/p' "$BASE_CONF" | head -n -1 2>/dev/null || sudo cat "$BASE_CONF"
+echo
+
+# ---------- 5. Clean up any stray conf.d autologin fragments from manual attempts ----------
+
+info "Removing any leftover manual conf.d autologin overrides (base config now handles it)"
+sudo rm -f /etc/plasmalogin.conf.d/zzz-steamos-autologin*.conf
+ok "Cleaned."
+echo
+
+# ---------- 6. Install the sync bridge: conf.d -> base config ----------
+#
+# CachyOS's own tools (steamos-session-select, Steam's "Switch to
+# Desktop", and cachyos-gamescope-autologin.service) only ever write the
+# session choice to /etc/plasmalogin.conf.d/zz-steamos-autologin.conf.
+# Since the base config wins, we need a watcher that copies that value
+# into the base file whenever it changes.
+
+SYNC_SCRIPT="/usr/local/bin/sync-steamos-session.sh"
+info "Installing session sync bridge at $SYNC_SCRIPT"
+
+sudo tee "$SYNC_SCRIPT" > /dev/null << 'EOF'
+#!/bin/bash
+# Copies the Session= value CachyOS's steamos tools write into
+# /etc/plasmalogin.conf.d/zz-steamos-autologin.conf back into the base
+# /etc/plasmalogin.conf, which plasma-login-manager actually obeys.
+SRC="/etc/plasmalogin.conf.d/zz-steamos-autologin.conf"
+DEST="/etc/plasmalogin.conf"
+
+[[ -f "$SRC" ]] || exit 0
+SESSION=$(grep -oP '^Session=\K.*' "$SRC")
+[[ -z "$SESSION" ]] && exit 0
+
+if grep -q '^Session=' "$DEST"; then
+    sed -i "s|^Session=.*|Session=$SESSION|" "$DEST"
+else
+    echo "Session=$SESSION" >> "$DEST"
+fi
+EOF
+
+sudo chmod +x "$SYNC_SCRIPT"
+ok "Sync script installed."
+echo
+
+# ---------- 7. systemd path watcher + service ----------
+
+info "Installing systemd path watcher so session switches take effect immediately"
+
+sudo tee /etc/systemd/system/sync-steamos-session.path > /dev/null << 'EOF'
+[Unit]
+Description=Watch for steamos session changes
+
+[Path]
+PathModified=/etc/plasmalogin.conf.d/zz-steamos-autologin.conf
+
+[Install]
+WantedBy=multi-user.target
+EOF
+
+sudo tee /etc/systemd/system/sync-steamos-session.service > /dev/null << 'EOF'
+[Unit]
+Description=Sync steamos session selection into plasmalogin.conf
+
+[Service]
+Type=oneshot
+ExecStart=/usr/local/bin/sync-steamos-session.sh
+EOF
+
+sudo systemctl daemon-reload
+sudo systemctl enable --now sync-steamos-session.path
+ok "Path watcher enabled."
+echo
+
+# ---------- 8. Run it once now so current state is in sync ----------
+
+info "Running the sync once now to align current state"
+sudo systemctl start sync-steamos-session.service
+ok "Done. Current base config:"
+sudo cat "$BASE_CONF"
+echo
+
+# ---------- 9. Summary + reboot ----------
+
+echo -e "${c_bold}Setup complete.${c_reset}"
+echo "What this did:"
+echo "  - Installed gamescope-session-cachyos, steam, mangohud (if missing)"
+echo "  - Created /etc/plasmalogin.conf.d (fixes Switch-to-Desktop crash)"
+echo "  - Set $BASE_CONF to autologin '$TARGET_USER' into gamescope, with Relogin=true"
+echo "  - Installed a sync bridge + systemd watcher so Steam's Switch-to-Desktop"
+echo "    (and cachyos-gamescope-autologin.service resetting back to gamescope"
+echo "    on logout) both actually take effect"
+echo
+echo "Backups of any files this script modified were saved with a"
+echo ".bak-gamescope-wizard suffix next to the original."
+echo
+echo "To manually flip sessions any time:"
+echo "  steamos-session-select gamescope   # boot straight into gamescope now"
+echo "  steamos-session-select plasma      # boot straight into desktop now"
+echo "  steamos-session-select persistent  # remember last-used session across reboots"
+echo "  steamos-session-select oneshot     # always start in gamescope regardless (default Deck behavior)"
+echo
+
+if ask_yn "Reboot now to test it?" n; then
+    sudo reboot
+else
+    info "Skipping reboot. Run 'sudo reboot' whenever you're ready to test."
+fi