Container Images

import PublishPrivateRegistry from "@cookbookContainer/_publish-private-registry.mdx"; import PublishPrivateRegistryMultiple from "@cookbookContainer/_publish-private-registry-multiple.mdx"; import ExportContainerImageToHost from "@cookbookContainer/_export-container-image-to-host.mdx"; import SetEnvVar from "@cookbookContainer/_set-env-var.mdx";

Dagger allows you to build, publish, and export container images, also known as just-in-time artifacts, as part of your Dagger Functions. This section shows you how to work with container images using Dagger with practical examples.

<PublishPrivateRegistry /> <PublishPrivateRegistryMultiple /> <ExportContainerImageToHost /> <SetEnvVar />

Use volatile variables for exec-time metadata

withVolatileVariable sets a non-secret environment variable for future withExec calls without invalidating exec cache when only the variable's value changes.

Typical examples include CI and reporting metadata such as:

• commit SHA
• branch or ref
• CI run ID

:::warning withVolatileVariable is an expert-only escape hatch. Use it only when you are certain that changing the variable alone must not invalidate cached withExec results. If that assumption is wrong, Dagger may reuse stale or incorrect cached results. :::

Unlike withEnvVariable, volatile variables:

• are visible only to future withExec calls
• are not persisted into the container image config
• are not returned by envVariable or envVariables
• are not available to expand: true

Use withEnvVariable for normal container configuration, withSecretVariable for sensitive values, and withVolatileVariable only for exec-time metadata that should not decide cache reuse.