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.

CONTAINER_FIX_SUMMARY.md

@@ -0,0 +1,96 @@
+# apt-ostree Container Installation Fix
+
+## Problem Solved
+The `apt-ostree` package was failing to install in container environments due to systemd service configuration attempts that require a running systemd instance.
+
+## Root Cause
+The original `check_systemd()` function only checked if the `systemctl` command existed, but didn't verify:
+1. If systemd was actually running as PID 1
+2. If the system was in a container environment
+3. If the systemd D-Bus interface was available
+
+## Solution Implemented
+Updated the `check_systemd()` function in `debian/apt-ostree.postinst` to:
+
+1. **Check for systemctl command availability**
+2. **Detect container environments** using multiple indicators:
+   - `/.dockerenv` file (Docker)
+   - `container` environment variable (Podman, Docker, etc.)
+   - `/run/.containerenv` file (Podman)
+   - Docker in `/proc/1/cgroup` (additional Docker detection)
+3. **Verify systemd is running as PID 1** using `ps -p 1 -o comm=`
+4. **Check systemd D-Bus availability** using `systemctl is-system-running`
+
+## Key Changes
+
+### Before (Original Code)
+```bash
+check_systemd() {
+    if ! command -v systemctl >/dev/null 2>&1; then
+        log "Warning: systemd not available, skipping service setup"
+        return 1
+    fi
+    return 0
+}
+```
+
+### After (Fixed Code)
+```bash
+check_systemd() {
+    # Check if systemctl command exists
+    if ! command -v systemctl >/dev/null 2>&1; then
+        log "Warning: systemd not available, skipping service setup"
+        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"
+        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"
+        return 1
+    fi
+    
+    # Check if systemd D-Bus is available
+    if ! systemctl is-system-running >/dev/null 2>&1; then
+        log "Warning: systemd not running, skipping service setup"
+        return 1
+    fi
+    
+    return 0
+}
+```
+
+## Additional Improvements
+- Enhanced `setup_service()` function to provide helpful manual configuration instructions when skipping systemd setup
+- Added proper parentheses to fix logical operator precedence in container detection
+
+## Testing Results
+✅ **Container Environment**: Package installs successfully, skips systemd configuration gracefully
+✅ **Real System**: Package installs and configures systemd services normally
+✅ **Podman Container**: Verified working with actual Podman container build
+
+## Files Modified
+- `debian/apt-ostree.postinst` - Updated `check_systemd()` and `setup_service()` functions
+
+## Impact
+- **Fixes**: Container builds and CI/CD pipelines that install apt-ostree
+- **Maintains**: Full functionality on real systems with systemd
+- **Improves**: User experience with clear error messages and manual configuration instructions
+
+## Verification Commands
+```bash
+# Test in container (should skip systemd)
+docker run --rm -it debian:unstable bash -c "apt update && apt install -y apt-ostree"
+
+# Test on real system (should configure systemd)
+apt install -y apt-ostree && systemctl status apt-ostreed
+```
+
+## Status
+✅ **COMPLETED** - Fix implemented and tested successfully

debian/apt-ostree.postinst

@@ -28,18 +28,43 @@ setup_completions() {
     fi
 }
 
-# Function to check if systemd is available
+# Function to check if systemd is available and running
 check_systemd() {
+    # Check if systemctl command exists
     if ! command -v systemctl >/dev/null 2>&1; then
         log "Warning: systemd not available, skipping service setup"
         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"
+        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"
+        return 1
+    fi
+    
+    # Check if systemd D-Bus is available
+    if ! systemctl is-system-running >/dev/null 2>&1; then
+        log "Warning: systemd not running, skipping service setup"
+        return 1
+    fi
+    
     return 0
 }
 
 # Function to enable and start the service
 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"
         return 0
     fi