Dockerfile instruction
A Dockerfile instruction is a declarative directive that specifies a build operation or image metadata during container image construction.
Learn Docker in a Month of Lunches, Second Edition
A Dockerfile instruction is a declarative directive that specifies a build action or image metadata.
- How it is used
- Packages applications into Docker images through ordered build actions and image configuration.
- How deep it goes
- Explains instruction order through cache reuse, layer contents, and worked builds; does not provide a full instruction reference.
- Examples
- Uses an edited JavaScript file, a Maven-built Java application, and copied files that remain in an image after deletion.
- What you can do after
- Build it from scratch: write and reorder Dockerfile instructions to package an application while reducing rebuild work and unwanted image contents.
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.NET in Action, Second Edition
A Dockerfile instruction is a directive written with an instruction keyword and arguments that controls image construction.
- How it is used
- Controls image construction and container startup for a .NET service.
- How deep it goes
- Defines syntax, base images, copying, startup, caching, and multi-stage builds, but not the full Dockerfile language.
- Examples
- Uses AsciiArtSvc Dockerfiles, .dockerignore entries, Docker build commands, and named build stages.
- What you can do after
- Operate/configure Docker to build and start a tagged .NET container image.
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Kubernetes in Action, Second Edition
A Dockerfile instruction is a declarative command that specifies one step in building a container image.
- How it is used
- Builds container images declaratively from a Dockerfile, with Docker processing each instruction during image creation.
- How deep it goes
- Explains base-image pulls, temporary containers, image layers, and tagging, but gives syntax detail only through one minimal example.
- Examples
- Uses FROM, COPY, and ENTRYPOINT in a minimal Node.js Dockerfile, then illustrates build output and image history.
- What you can do after
- Builds a tagged image with docker build and inspects it with docker images or docker history.
Read how Kubernetes in Action, Second Edition explains Dockerfile instruction →
Related concepts
- Dockerfilepart of · A Dockerfile is a text file containing declarative instructions for building a container image and specifying its contents and runtime metadata.
- image layerproduces · An image layer is an immutable filesystem change set that contributes to a layered container image and may be stored, cached, or shared independently.
- healthcheck instructionincludes · The HEALTHCHECK instruction is a Dockerfile instruction that defines a command and scheduling parameters for testing an application's health in a container.
- build cacheconfigures · A build cache is a storage mechanism that preserves completed build-task outputs for reuse when the relevant inputs have not changed.
- commandcontrasts with · A command is an instruction or request representing an operation for a system or component to interpret, handle, or execute.
- copy instructionincludes · The Dockerfile COPY instruction copies files or directories from a build context or another build stage into an image’s filesystem.
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