Run yamllint Inside Docker Container on Linux

The yamllint is a command line tool used to check YAML files for syntax errors, formatting issues, and best practices. It helps ensure that YAML files are well-formed and follow consistent styling rules.

This tutorial explains how to run yamllint inside Docker container on Linux. Commands have been tested on Ubuntu.

First, we need a sample YAML project to work with. You can clone the following GitHub repository that contains YAML files:

git clone https://github.com/eazybytes/yaml && cd yaml

This will download the repository and navigate into the project directory.

Instead of installing yamllint manually, we can use a pre-built Docker image. Run the following command inside the project directory:

docker run -it --rm -v ./:/code pipelinecomponents/yamllint yamllint .

Explanation of the command:

• docker run - runs a new container.
• -it - starts an interactive terminal session.
• --rm - removes the container after execution to keep things clean.
• -v ./:/code - mounts the current directory (./) into the container at /code. This allows yamllint inside the container to access the local files.
• pipelinecomponents/yamllint - specifies the Docker image to use.
• yamllint . - runs yamllint against all YAML files in the current directory.

After running the command, yamllint will analyze the YAML files and output any warnings or errors. A sample output might look like this:

./07_collections/collections.yml
  2:1       warning  missing document start "---"  (document-start)
  39:17     error    no new line character at the end of file  (new-line-at-end-of-file)

You can customize the linting rules by creating a .yamllint.yaml configuration file in the project root. Here's a simple example:

.yamllint.yaml

extends: default

rules:
  document-start: disable

Then, run yamllint again using the same Docker command to apply the new rules.