# Implementation Overview

## Summary

This project creates a single bootable ISO that automatically configures itself as part of a Kubernetes cluster with integrated distributed services (Ceph, Kafka, MQTT, DNS). All services are managed directly by systemd.

## Architecture

### Boot Flow

```
┌─────────────────────────────────────────────────────────┐
│ 1. System Boots from ISO                                │
└────────────────┬────────────────────────────────────────┘
                 │
                 ▼
┌─────────────────────────────────────────────────────────┐
│ 2. cluster-detect.service (Very Early Boot)             │
│    - Runs cluster-detect.sh                             │
│    - Detects node identity (MAC/IP/hostname)            │
│    - Creates /etc/cluster-config/current-node.yaml      │
│    - Writes /etc/cluster-config/node-identity           │
└────────────────┬────────────────────────────────────────┘
                 │
                 ▼
┌─────────────────────────────────────────────────────────┐
│ 3. Environment File Generation                          │
│    - Runs generate-environment-files.sh                 │
│    - Creates /etc/cluster-config/environment/*.env      │
│    - Extracts node IP, cluster settings, etc.           │
└────────────────┬────────────────────────────────────────┘
                 │
                 ▼
┌─────────────────────────────────────────────────────────┐
│ 4. Role Activation                                      │
│    - Runs cluster-activate-roles.sh                     │
│    - Maps roles to systemd targets                      │
│    - Enables and starts targets                         │
└────────────────┬────────────────────────────────────────┘
                 │
                 ▼
┌─────────────────────────────────────────────────────────┐
│ 5. Service Startup (Dependency Order)                   │
│    - containerd.service                                 │
│    - etcd.service (masters only)                        │
│    - kube-apiserver.service (masters only)              │
│    - kube-controller-manager.service (masters only)     │
│    - kube-scheduler.service (masters only)              │
│    - kubelet.service (all nodes)                        │
│    - kafka.service (kafka nodes)                        │
│    - ceph-mon@.service (ceph-mon nodes)                 │
│    - ceph-osd@.service (ceph-osd nodes)                 │
│    - mosquitto.service (mqtt nodes)                     │
│    - coredns.service (dns nodes)                        │
└─────────────────────────────────────────────────────────┘
```

## Components

### Configuration Files (configs/)

#### cluster.yaml
- Defines entire cluster topology
- Lists all nodes with IPs, hostnames, roles
- Specifies enabled services
- Network configuration (pod CIDR, service CIDR)

#### services/*.yaml (5 files)
- kubernetes.yaml - K8s component configuration
- ceph.yaml - Ceph storage settings
- kafka.yaml - Kafka broker configuration
- mqtt.yaml - MQTT broker settings
- dns.yaml - CoreDNS configuration

#### nodes/*.yaml (5 files)
- master-01.yaml - Control plane node
- worker-01.yaml - Worker node
- worker-02.yaml - Worker + Ceph OSD
- kafka-01.yaml - Worker + Kafka broker
- storage-01.yaml - Worker + Ceph mon + OSD

### Systemd Units (systemd/)

#### Services (11 files)
1. **containerd.service** - Container runtime for Kubernetes
2. **kubelet.service** - Kubernetes node agent
3. **kube-apiserver.service** - Kubernetes API server
4. **kube-controller-manager.service** - K8s controller manager
5. **kube-scheduler.service** - K8s scheduler
6. **etcd.service** - Key-value store for K8s
7. **kafka.service** - Kafka broker (KRaft mode)
8. **ceph-mon@.service** - Ceph monitor (template)
9. **ceph-osd@.service** - Ceph OSD (template)
10. **mosquitto.service** - MQTT broker
11. **coredns.service** - DNS server

#### Targets (7 files)
- **kubernetes-master.target** - Pulls in K8s control plane services
- **kubernetes-worker.target** - Pulls in kubelet
- **kafka.target** - Pulls in Kafka broker
- **ceph-mon.target** - Pulls in Ceph monitor
- **ceph-osd.target** - Pulls in Ceph OSD
- **mqtt.target** - Pulls in Mosquitto
- **dns.target** - Pulls in CoreDNS

#### Special Service
- **cluster-detect.service** - Runs very early to detect node identity

### Tools (tools/)

#### Core Scripts (12 files)

**Detection & Activation:**
1. **cluster-detect.sh** - Node identity detection (MAC/IP/hostname)
2. **cluster-activate-roles.sh** - Map roles to systemd targets
3. **generate-environment-files.sh** - Create env files for services

**Service Configuration Generators:**
4. **kubelet-config-generator.sh** - Generate kubelet config.yaml
5. **kube-apiserver-config-generator.sh** - Pre-start checks for API server
6. **etcd-config-generator.sh** - Initialize etcd data directory
7. **kafka-config-generator.sh** - Generate Kafka server.properties
8. **ceph-mon-init.sh** - Initialize Ceph monitor
9. **ceph-osd-init.sh** - Initialize Ceph OSD
10. **mosquitto-config-generator.sh** - Generate mosquitto.conf
11. **coredns-config-generator.sh** - Generate CoreDNS Corefile

**Validation:**
12. **validate-config.py** - Validate cluster configuration before build

## Role-to-Target Mapping

| Role | Systemd Target | Services Started |
|------|----------------|------------------|
| master / control-plane | kubernetes-master.target | kubelet, kube-apiserver, kube-controller-manager, kube-scheduler, etcd |
| worker | kubernetes-worker.target | kubelet |
| kafka-broker | kafka.target | kafka |
| ceph-mon | ceph-mon.target | ceph-mon@node |
| ceph-osd | ceph-osd.target | ceph-osd@X (per device) |
| mqtt-broker | mqtt.target | mosquitto |
| dns-server | dns.target | coredns |

## File Locations (On Installed System)

### Configuration
```
/etc/cluster-config/
├── cluster.yaml                    # Full cluster topology
├── current-node.yaml               # Symlink to this node's config
├── node-identity                   # This node's name
├── services/                       # Service configs
│   ├── kubernetes.yaml
│   ├── ceph.yaml
│   ├── kafka.yaml
│   ├── mqtt.yaml
│   └── dns.yaml
├── nodes/                          # All node configs
│   ├── master-01.yaml
│   ├── worker-01.yaml
│   └── ...
└── environment/                    # Generated env files
    ├── kubelet.env
    ├── kube-apiserver.env
    ├── kafka.env
    └── ...
```

### Scripts
```
/usr/local/bin/
├── cluster-detect.sh
├── cluster-activate-roles.sh
├── generate-environment-files.sh
├── kubelet-config-generator.sh
├── kafka-config-generator.sh
└── ...
```

### Systemd Units
```
/etc/systemd/system/
├── cluster-detect.service
├── containerd.service
├── kubelet.service
├── kube-apiserver.service
├── kubernetes-master.target
├── kafka.service
└── ...
```

### Data Directories
```
/var/lib/
├── kubelet/                        # Kubelet data and configs
├── etcd/                          # etcd data
├── kafka/                         # Kafka logs and data
├── ceph/                          # Ceph data
│   ├── mon/
│   └── osd/
└── mosquitto/                     # MQTT persistence
```

## Configuration Generation Process

1. **Build time**: User edits configs/ directory
2. **Validation**: `validate-config.py` ensures correctness
3. **ISO creation**: All configs embedded into ISO (future work)
4. **First boot**: `cluster-detect.sh` identifies node
5. **Environment generation**: `generate-environment-files.sh` creates .env files
6. **Service startup**: Each service's ExecStartPre runs config generator
7. **Runtime**: Services read from generated configs

## Security Considerations

### PKI/Certificates
- **Kubernetes**: Requires CA, API server, kubelet, etcd certs
- **Ceph**: Requires cephx authentication keys
- **MQTT**: Password file and ACLs

**TODO**: Certificate generation not yet implemented

### Service Hardening
All services use systemd security features:
- `NoNewPrivileges=true`
- `ProtectHome=true`
- `ProtectSystem=strict/full`
- `PrivateTmp=true`
- Limited capabilities (where applicable)

## Next Steps

### Critical Path to Working System
1. **Certificate/Key Generation**
   - Script to generate Kubernetes PKI
   - Script to generate Ceph keys
   - MQTT password management

2. **Network Configuration**
   - Static IP assignment
   - Network interface configuration
   - Calico CNI installation

3. **Cluster Bootstrapping**
   - First master initialization
   - Join tokens for workers
   - Multi-master etcd cluster setup
   - Ceph cluster initialization

4. **ISO Builder**
   - Take configs/ + base OS → bootable ISO
   - Integrate kickstart/cloud-init
   - Embed all scripts and systemd units

### Nice to Have
- Monitoring (Prometheus/Grafana)
- Logging (Loki/journald)
- Update mechanism
- Rollback support
- Interactive TUI for node selection
- Web dashboard for cluster status

## Testing Strategy

### Unit Testing
- Validate each config generator script
- Test role-to-target mapping
- Verify YAML parsing

### Integration Testing
- Boot test in VMs
- Multi-node cluster formation
- Service startup ordering
- Failure recovery

### End-to-End Testing
- Full cluster deployment
- Workload deployment
- Storage provisioning
- Message broker connectivity

## Known Limitations

1. **Certificate generation not implemented** - Manual PKI setup required
2. **Single master only** - Multi-master etcd cluster needs work
3. **No network config** - Assumes static IPs or DHCP reservations
4. **Ceph bootstrap incomplete** - Mon/OSD initialization stubs only
5. **No update mechanism** - Fresh install only
6. **No secrets management** - Passwords and keys in plain text

## Project Statistics

- **Configuration files**: 11 (1 cluster + 5 services + 5 nodes)
- **Systemd units**: 19 (11 services + 7 targets + 1 cluster-detect)
- **Scripts**: 12 tools
- **Total files**: 42+
- **Lines of code**: ~2500+ (estimated)

## References

- [Kubernetes Documentation](https://kubernetes.io/docs/)
- [Ceph Documentation](https://docs.ceph.com/)
- [Kafka Documentation](https://kafka.apache.org/documentation/)
- [systemd Documentation](https://systemd.io/)
- [CoreDNS Documentation](https://coredns.io/)