Run instruction
A Dockerfile RUN instruction executes a command during container image construction, producing filesystem changes that become part of the resulting image.
Learn Docker in a Month of Lunches, Second Edition
The RUN instruction executes a command while building a Docker image and commits its result to an image layer.
- How it is used
- Executes build-time commands for generating files, retrieving dependencies, compiling applications, and testing across Dockerfile stages.
- How deep it goes
- Explains execution, command availability, image layers, failure behavior, caching, multi-stage placement, and platform portability.
- Examples
- Uses echo file generation, Maven dependency retrieval, Maven packaging, and a multi-stage Dockerfile that copies generated artifacts.
- What you can do after
- Builds Docker images that generate artifacts, compile applications, reuse cached steps, and isolate build tools from runtime stages.
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Podman in Action: Secure, rootless containers for Kubernetes, microservices, and more
The RUN directive executes a command in an intermediate container during image construction.
- How it is used
- Builds container images by running installation, update, and cleanup commands during image construction.
- How deep it goes
- Explains build-container execution and committed layers, but gives only one command example rather than detailed syntax variations.
- Examples
- Uses yum to update packages, install procps-ng, and clean package metadata so the image contains ps with less cruft.
- What you can do after
- Apply it via Podman to install packages and modify an image while preserving changes for subsequent build steps.
Related concepts
- 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.
- cmd directivecontrasts with · The Dockerfile CMD instruction specifies the default command or arguments executed when a container starts, unless overridden at runtime.
- code compilationimplements · Code compilation is the translation of source code or another formal representation into an executable, intermediate, or lower-level representation.
- dependencyuses · A software dependency is a component, resource, or prerequisite on which another software component or operation relies to function or proceed.
- FluentBitconfigures · Fluent Bit is a lightweight, open-source telemetry agent for collecting, processing, enriching, and forwarding logs and other event data.
- Dockerfilepart of · A Dockerfile is a text file containing declarative instructions for building a container image and specifying its contents and runtime metadata.
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