Fix apt-ostree container installation failure

- Enhanced check_systemd() function to properly detect container environments
- Added detection for Docker, Podman, and other container runtimes
- Verify systemd is running as PID 1 before attempting service operations
- Check systemd D-Bus availability before service configuration
- Gracefully skip systemd setup in containers with helpful messages
- Provide manual configuration instructions for real systems

Fixes container builds and CI/CD pipelines that install apt-ostree
while maintaining full functionality on real systems with systemd.

debian/apt-ostree.postinst

@@ -36,25 +36,79 @@ check_systemd() {
         return 1
     fi
     
-    # Check if we're in a container environment
-    if [ -f /.dockerenv ] || [ -n "${container:-}" ] || [ -f /run/.containerenv ] || \
-       ([ -f /proc/1/cgroup ] && grep -q docker /proc/1/cgroup 2>/dev/null); then
-        log "Warning: Running in container environment, skipping systemd service setup"
+    # Enhanced container environment detection
+    local in_container=false
+    
+    # Check for Docker container indicators
+    if [ -f /.dockerenv ]; then
+        log "Detected Docker container environment"
+        in_container=true
+    fi
+    
+    # Check for Podman container indicators
+    if [ -f /run/.containerenv ]; then
+        log "Detected Podman container environment"
+        in_container=true
+    fi
+    
+    # Check for container environment variable
+    if [ -n "${container:-}" ]; then
+        log "Detected container environment (container=${container})"
+        in_container=true
+    fi
+    
+    # Check cgroup for container indicators
+    if [ -f /proc/1/cgroup ]; then
+        if grep -qE "(docker|podman|containerd|kubepods)" /proc/1/cgroup 2>/dev/null; then
+            log "Detected container environment via cgroup"
+            in_container=true
+        fi
+    fi
+    
+    # Check for systemd-nspawn container
+    if [ -f /run/systemd/container ]; then
+        local container_type
+        container_type=$(cat /run/systemd/container 2>/dev/null || echo "")
+        if [ -n "$container_type" ]; then
+            log "Detected systemd-nspawn container (type: $container_type)"
+            in_container=true
+        fi
+    fi
+    
+    # Check for LXC container
+    if [ -f /proc/1/environ ] && grep -q "container=lxc" /proc/1/environ 2>/dev/null; then
+        log "Detected LXC container environment"
+        in_container=true
+    fi
+    
+    # If in container, skip systemd setup
+    if [ "$in_container" = true ]; then
+        log "Running in container environment, skipping systemd service setup"
+        log "Container environments typically don't run systemd as PID 1"
         return 1
     fi
     
     # Check if systemd is actually running as PID 1
-    if ! ps -p 1 -o comm= | grep -q systemd; then
-        log "Warning: systemd not running as PID 1, skipping service setup"
+    local init_process
+    init_process=$(ps -p 1 -o comm= 2>/dev/null || echo "")
+    if [ "$init_process" != "systemd" ]; then
+        log "Warning: systemd not running as PID 1 (init process: ${init_process:-unknown}), skipping service setup"
         return 1
     fi
     
-    # Check if systemd D-Bus is available
+    # Check if systemd D-Bus is available and responsive
     if ! systemctl is-system-running >/dev/null 2>&1; then
-        log "Warning: systemd not running, skipping service setup"
+        log "Warning: systemd D-Bus not available or not running, skipping service setup"
         return 1
     fi
     
+    # Additional check: verify we can actually communicate with systemd
+    if ! systemctl list-units --type=service >/dev/null 2>&1; then
+        log "Warning: Cannot communicate with systemd, skipping service setup"
+        return 1
+    fi
+    
+    log "Systemd environment verified, proceeding with service setup"
     return 0
 }
 
@@ -62,34 +116,57 @@ check_systemd() {
 setup_service() {
     if ! check_systemd; then
         log "Skipping systemd service configuration"
-        log "To configure services manually on a real system, run:"
-        log "  systemctl enable apt-ostreed.service"
-        log "  systemctl start apt-ostreed.service"
+        log ""
+        log "=== Manual Configuration Instructions ==="
+        log "To configure apt-ostreed service on a real system with systemd:"
+        log "  1. Enable the service: systemctl enable apt-ostreed.service"
+        log "  2. Start the service: systemctl start apt-ostreed.service"
+        log "  3. Check status: systemctl status apt-ostreed.service"
+        log ""
+        log "For container environments:"
+        log "  - apt-ostreed service is not needed in containers"
+        log "  - Use 'apt-ostree' commands directly as needed"
+        log "  - Service will be available when running on real systems"
+        log ""
         return 0
     fi
 
     log "Setting up apt-ostreed service..."
 
-    # Reload systemd daemon
-    systemctl daemon-reload
+    # Reload systemd daemon to pick up new service files
+    if systemctl daemon-reload; then
+        log "Systemd daemon reloaded successfully"
+    else
+        log "Warning: Failed to reload systemd daemon"
+        return 1
+    fi
 
     # Enable the service
     if systemctl enable apt-ostreed.service; then
-        log "apt-ostreed service enabled"
+        log "apt-ostreed service enabled successfully"
     else
-        log "Warning: Failed to enable apt-ostreed service"
+        log "Error: Failed to enable apt-ostreed service"
+        return 1
     fi
 
     # Start the service if not running
     if ! systemctl is-active --quiet apt-ostreed.service; then
         if systemctl start apt-ostreed.service; then
-            log "apt-ostreed service started"
+            log "apt-ostreed service started successfully"
         else
-            log "Warning: Failed to start apt-ostreed service"
+            log "Warning: Failed to start apt-ostreed service (may need manual intervention)"
+            log "Try running: systemctl status apt-ostreed.service"
         fi
     else
         log "apt-ostreed service already running"
     fi
+    
+    # Verify service is working
+    if systemctl is-active --quiet apt-ostreed.service; then
+        log "apt-ostreed service is active and running"
+    else
+        log "Warning: apt-ostreed service is not active"
+    fi
 }
 
 # Function to setup directories and permissions