Initial commit - Phase 3/4

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/apply-cpu-cores.sh

@@ -0,0 +1,86 @@
+#!/bin/bash
+# Apply CPU cores defaults to cmdline.txt (fallback for manual installations)
+# Used by dangerous-pi-cpu-cores.service
+#
+# NOTE: When using the official pi-gen image, maxcpus is already set during build.
+# This script only runs as a fallback for manual installations.
+#
+# On Pi Zero 2 W (and other ARM devices), CPU hotplug via sysfs does NOT work.
+# Instead, we use the maxcpus=N kernel parameter in cmdline.txt.
+# This script sets the default maxcpus for Pi Zero 2 W if not already configured.
+
+LOG_TAG="dangerous-pi-cpu-cores"
+
+log() {
+    logger -t "$LOG_TAG" "$1"
+    echo "$1"
+}
+
+# Find cmdline.txt (location varies by Pi OS version)
+find_cmdline() {
+    if [ -f /boot/firmware/cmdline.txt ]; then
+        echo "/boot/firmware/cmdline.txt"
+    elif [ -f /boot/cmdline.txt ]; then
+        echo "/boot/cmdline.txt"
+    else
+        echo ""
+    fi
+}
+
+CMDLINE_FILE=$(find_cmdline)
+
+if [ -z "$CMDLINE_FILE" ]; then
+    log "ERROR: Could not find cmdline.txt"
+    exit 1
+fi
+
+# Check if maxcpus is already configured
+if grep -q "maxcpus=" "$CMDLINE_FILE"; then
+    CURRENT=$(grep -o 'maxcpus=[0-9]*' "$CMDLINE_FILE" | cut -d= -f2)
+    log "maxcpus already configured: $CURRENT cores"
+    exit 0
+fi
+
+# Determine default cores based on Pi model
+get_default_cores() {
+    local model=""
+    local total_cores=$(nproc --all)
+
+    if [ -f /proc/device-tree/model ]; then
+        model=$(cat /proc/device-tree/model | tr -d '\0')
+    fi
+
+    # Pi Zero 2 W has 4 cores but should default to 2 for thermal management
+    if echo "$model" | grep -q "Pi Zero 2"; then
+        echo 2
+    # Single-core Pis - no need to set maxcpus
+    elif echo "$model" | grep -q "Pi Zero W\|Pi Zero$\|Pi 1\|Pi Model A\|Pi Model B"; then
+        echo "$total_cores"  # Return total (no restriction needed)
+    # All other multi-core Pis use all cores by default
+    else
+        echo "$total_cores"
+    fi
+}
+
+DEFAULT_CORES=$(get_default_cores)
+TOTAL_CORES=$(nproc --all)
+
+# Only set maxcpus if we want fewer than total cores
+if [ "$DEFAULT_CORES" -lt "$TOTAL_CORES" ]; then
+    log "Setting default maxcpus=$DEFAULT_CORES for this device"
+
+    # Backup original
+    cp "$CMDLINE_FILE" "${CMDLINE_FILE}.bak"
+
+    # Append maxcpus to cmdline
+    CURRENT_CMDLINE=$(cat "$CMDLINE_FILE" | tr -d '\n')
+    echo "$CURRENT_CMDLINE maxcpus=$DEFAULT_CORES" > "${CMDLINE_FILE}.new"
+    mv "${CMDLINE_FILE}.new" "$CMDLINE_FILE"
+
+    log "Updated $CMDLINE_FILE with maxcpus=$DEFAULT_CORES"
+    log "NOTE: This will take effect on next reboot"
+else
+    log "No maxcpus restriction needed (using all $TOTAL_CORES cores)"
+fi
+
+exit 0