ADR-001: Agent-based Installation Approach for OpenShift Deployment

Date

2025-03-09

Status

Accepted

Decision Makers

• OpenShift Platform Team
• Infrastructure Architecture Team

Context

OpenShift Container Platform requires a reliable, flexible installation method that can:

• Work in both connected and disconnected environments
• Support air-gapped installations
• Handle various infrastructure types (bare metal, VMware, etc.)
• Support advanced networking configurations
• Work consistently across different CPU architectures

The traditional installation methods have limitations in disconnected environments and require complex infrastructure setup.

Considered Options

1. Installer-Provisioned Infrastructure (IPI)

• Pros:
  • Automated infrastructure provisioning
  • Integrated with cloud providers
• Cons:
  • Requires internet connectivity
  • Limited flexibility in disconnected environments
  • Complex infrastructure requirements

2. User-Provisioned Infrastructure (UPI)

• Pros:
  • More control over infrastructure
  • Works in disconnected environments
• Cons:
  • Manual infrastructure setup
  • Complex orchestration required
  • Higher risk of human error

3. Agent-based Installation (Selected)

• Pros:
  • Works offline and in air-gapped environments
  • Combines ease of use of Assisted Installation
  • Flexible server boot options
  • Platform-agnostic approach
  • Supports advanced networking (bonds, VLANs, SR-IOV)
• Cons:
  • Requires bootable ISO creation
  • Initial setup complexity

Decision

We chose the Agent-based Installation approach because it provides:

1. Maximum flexibility for different environments
2. Support for disconnected and air-gapped installations
3. Built-in validation and automation capabilities
4. Platform-agnostic deployment options

Implementation

Core Components

1. Agent Discovery Service
   • Embedded in bootable ISO
   • Handles node discovery and configuration
2. Configuration Management
   • install-config.yaml for cluster configuration
   • agent-config.yaml for host-specific settings
3. Network Configuration
   • Support for DHCP and static IP
   • Advanced networking (bonds, VLANs)
   • SR-IOV capability

Example Structure

examples/
├── baremetal-example/
├── vmware-example/
├── sno-bond0-signal-vlan/
└── various network configurations/

Consequences

Positive

1. Simplified deployment in disconnected environments
2. Consistent installation experience across platforms
3. Reduced dependency on external services
4. Flexible networking configuration
5. Support for all major CPU architectures

Negative

1. Initial learning curve for ISO creation
2. Additional storage requirements for ISO
3. Boot media management overhead

Related

• Installation Guide
• Configuration Guide
• Network Configuration
• Example Configurations

Notes

This approach is particularly well-suited for:

• Edge computing deployments
• Highly secure environments
• Multi-architecture deployments
• Complex networking requirements

Test Cases

Key test cases are implemented in the e2e-tests directory: ```bash e2e-tests/ ├── bootstrap_env.sh ├── run_e2e.sh └── validate_env.sh