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Container Image Inspector

The Container Image Inspector analyzes Docker images to identify excessively large layers and retrieve detailed metadata. It helps developers and DevOps engineers optimize image sizes and understand the build history of a container.

Syntax

opsforge cloud image-inspect [IMAGE_NAME]

Arguments

  • IMAGE_NAME: The name or ID of the local Docker image (e.g., nginx:latest).

Usage Examples

Inspect a local image

opsforge cloud image-inspect my-app:v1

Data Extracted

  • Layer History: Breaks down the image into its constituent layers, showing the size of each layer and the Dockerfile command (CreatedBy) that generated it.
  • Architecture/OS: Displays the target CPU architecture (e.g., amd64) and operating system.
  • Author: Shows the image author/maintainer if specified in the metadata.

Technical Details

This tool acts as a wrapper around the docker inspect and docker history commands. It parses the resulting JSON and formatted output to provide a clean, readable summary in the terminal.

[!IMPORTANT] Prerequisites: This tool requires the Docker Desktop or Docker Engine to be installed and running on the local system. The image must also be available locally (i.e., you must run docker pull first if the image is in a remote registry).

Optimization Tips

  • Multi-stage builds: Use multi-stage builds to keep the final image small by excluding build-time dependencies.
  • Combine RUN commands: Combine multiple apt-get or pip install commands into a single RUN instruction to reduce the number of layers.
  • Clear Caches: Always clear package manager caches (e.g., rm -rf /var/lib/apt/lists/*) in the same layer they were created.