DO188 – Red Hat OpenShift Development I: Introduction to Containers with Podman — Lesson 2: Containerfiles, Image Builds, Layers, Tags, Rootless Containers, and Security

Learning Objectives

• Explain the structures, services, data, settings, roles, and dependencies governing Containerfiles and image builds.
• Implement and validate layers and tags, rootless containers, and container security using reviewable evidence.
• Evaluate the condition where a change succeeds in one environment but fails elsewhere because inventory, policy, version, or runtime assumptions differ and select a proportionate corrective response.

Detailed Topics

• Containerfiles applied to the course scenario, expected platform behavior, dependencies, controls, and evidence.
• image builds applied to the course scenario, expected platform behavior, dependencies, controls, and evidence.
• layers and tags applied to the course scenario, expected platform behavior, dependencies, controls, and evidence.
• rootless containers applied to the course scenario, expected platform behavior, dependencies, controls, and evidence.
• container security applied to the course scenario, expected platform behavior, dependencies, controls, and evidence.

Instructor Demonstration

The instructor traces a development team preparing secure container images and local workflows for deployment to OpenShift. The walkthrough connects navigation, commands, configuration logic, system messages, and evidence captured in the container image repository, Podman workflow record, security checks, and OpenShift deployment evidence. It also tests the exception where a change succeeds in one environment but fails elsewhere because inventory, policy, version, or runtime assumptions differ.

Hands-On Exercise

Complete a controlled Red Hat exercise covering Containerfiles, Image Builds, Layers, Tags, Rootless Containers, and Security and preserve the verified result in the container image repository, Podman workflow record, security checks, and OpenShift deployment evidence.

1. Confirm scope, prerequisites, versions, identities, dependencies, and acceptance criteria.
2. Execute the workflow while recording commands, settings, outputs, events, and system messages.
3. Test normal behavior, one boundary condition, and the stated exception.
4. Document corrections, evidence, ownership, retest criteria, rollback, and handover actions.

Scenario Analysis

• Identify which object, service, policy, setting, or sequence most strongly influences Containerfiles.
• Compare two defensible responses and explain technical, security, operational, and support trade-offs.
• Determine how the container image repository, Podman workflow record, security checks, and OpenShift deployment evidence should be approved, retained, retested, and updated.

Troubleshooting Guidance

Start where expected behavior first differs from the observed result. Check prerequisites, identity, configuration order, version compatibility, connectivity, status, resource limits, and evidence separately. Treat “a change succeeds in one environment but fails elsewhere because inventory, policy, version, or runtime assumptions differ” as a hypothesis until commands, logs, settings, and retest outcomes confirm the cause.

Validation Checklist

• Required platform components, identities, permissions, settings, and dependencies are present.
• The container image repository, Podman workflow record, security checks, and OpenShift deployment evidence connects each conclusion to objective, reviewable evidence.
• Normal processing, a boundary condition, dependency behavior, and the stated exception were tested.
• Corrections, ownership, retest criteria, rollback, documentation, and operational handover are complete.

Lesson Outcome

Learners can apply Containerfiles, Image Builds, Layers, Tags, Rootless Containers, and Security, explain the resulting platform behavior, and defend the outcome through the container image repository, Podman workflow record, security checks, and OpenShift deployment evidence.