FR-IMG-003 — Immutable Infrastructure Workflows

Go to Crucible Image Management Requirements

Statement

Crucible SHALL replace an existing deployed image with a newly built image rather than modifying the deployed_image in place.

Source Statement

The system shall support immutable infrastructure workflows.

Source

Crucible System Requirements Specification, Version 1.1 Draft, Functional Requirements, FR-IMG-003.

Assessment

The source statement expresses the approved intent but does not provide a fully testable formulation.

The following Specification Discipline and Authoring findings apply:

The system does not use the defined system nameshall does not follow the established uppercase normative conventionSupport is a weak verb that does not identify the required behaviorImmutable infrastructure workflows names a practice but does not identify the operation Crucible performsThe source statement does not identify the subject that remains unmodifiedThe source statement does not identify how a required change is appliedThe source statement does not distinguish replacement from in-place modificationThe source statement does not require signing, verification, promotion, rollback, or deployment validationThe normalized Statement:

Replaces The system with CrucibleReplaces support with the direct behavior replaceIdentifies the existing deployed image as the subject that is not modified in placeIdentifies a newly built image as the replacementExpresses the distinguishing behavior of an immutable infrastructure workflowRetains one primary required behaviorThe normalized Statement does not require a particular virtualization platform, container runtime, image format, deployment mechanism, or replacement algorithm.

Rationale

An immutable infrastructure workflow applies a required change by building and deploying a replacement image rather than modifying the existing deployed image.

This approach preserves the relationship between a deployed subject and the image Artifact from which the subject was created.

Replacement-based image workflows contribute to:

Consistent deployed stateReduced configuration driftRepeatable deploymentControlled image changesRecovery through replacementComparison of prior and succeeding image RevisionsReproducibilityProvenanceTraceabilityA newly built image may incorporate:

Updated softwareUpdated configurationUpdated Image LayersUpdated security controlsUpdated operating-system contentCorrective changesA new Revision of an applicable BaselineThe workflow then replaces the existing deployed image with the newly built image.

FR-IMG-003 does not prohibit changes to external stateful resources, persistent data, credentials, network resources, or other subjects that remain separate from the deployed image.

Applies To

This requirement applies to:

Container imagesDeployed imagesReplacement imagesImage RevisionsImage build workflowsImage replacement workflowsVirtual machinesContainerized workloadsInfrastructure EnvironmentsCI/CD Pipelines

Verification

Verification SHALL confirm that a required change produces a newly built imageVerification SHALL confirm that Crucible replaces the existing deployed image with the newly built imageVerification SHALL confirm that Crucible does not modify the existing deployed image in placeVerification may include:

Machine Image replacement testingContainer-image replacement testingDeployed-image inspectionImage-Revision comparisonDeployment-log inspectionFile-system comparisonConfiguration-drift inspectionAutomated CI/CD Pipeline testingThe verification record SHALL identify:

The existing deployed imageThe required changeThe newly built imageThe replacement operationThe observed state of the existing deployed imageThe observed state of the replacement imageThe replacement resultThe generated Evidence

Outgoing Traceability

This requirement realizes:

This requirement relates to:

Referenced By

The wiki Backlinks function provides the current list of pages that reference FR-IMG-003.

Incoming Traceability should be derived dynamically from backlinks rather than maintained as a duplicate manual list.

Backlinks identify incoming references but do not define the semantics of each relationship. Referencing pages should identify whether the relationship represents realization, refinement, verification, dependency, or another defined traceability relationship.

ConOps Relationship

The Crucible Concept of Operations describes a Phase 1 workflow that builds controlled image Artifacts and deploys infrastructure through automated CI/CD Pipeline activities.

FR-IMG-003 establishes that image changes use replacement-based workflow behavior rather than modification of an existing deployed image in place.

Requirements governing image build, signing, verification, promotion, deployment, rollback, and validation define separate behavior within the broader workflow.

Delivery Phase

Phase 1

Implementation Status

Not Assessed

Implementation status requires verification that Crucible replaces an existing deployed image with a newly built image rather than modifying the deployed image in place.

Requirement Status

Draft

The source System Requirements Specification identifies Version 1.1 as a draft.

Notes for Editors

This requirement page should retain the stable requirement identifier FR-IMG-003.

Changes to the Statement SHALL preserve the approved intent of the source requirement.

The Source Statement should preserve the original wording from the controlling System Requirements Specification.

The Statement should remain limited to replacement-based image workflow behavior.

Requirements for building, signing, verifying, promoting, deploying, rolling back, and validating images should remain in their applicable requirement pages.

Verification criteria should test only the behavior stated in the normalized Statement and should not introduce additional normative obligations.

Incoming Traceability should use the wiki Backlinks function rather than a manually maintained list.

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