Dockle — Container Image Linter for Security, Helping build the Best-Practice Docker Image, Easy to start

1. So what is Dockle

Dockle is an open-source container linter that focuses on security aspects of Docker images. It helps identify potential security issues and suggests best practices for building Docker images. Here are some key features of Dockle:

• Security Best Practices: Dockle checks for common security vulnerabilities and misconfigurations in Docker images.
• Easy to Use: It is straightforward to set up and use, making it accessible for developers at any level.
• Integration: Dockle can be integrated into CI/CD pipelines to automate security checks for Docker images.
• Detailed Reports: It provides detailed reports with recommendations on how to fix identified issues.
• Open Source: Dockle is open-source, meaning it is free to use and can be customized as per your requirements.

By using Dockle, developers can ensure that their Docker images adhere to security best practices, reducing the risk of deploying vulnerable containers.

2. Now What is Linter..?

A linter is a tool that analyzes source code to identify potential errors, bugs, stylistic errors, and other issues. Linters are commonly used in software development to improve code quality, ensure adherence to coding standards, and catch potential problems early in the development process. Here are some key aspects of linters:

• Static Analysis: Linters perform static code analysis, meaning they examine the code without executing it. This allows them to identify issues that might not be apparent during runtime.
• Error Detection: Linters can catch a wide range of issues, from syntax errors and undefined variables to more complex problems like potential security vulnerabilities or inefficient code practices.
• Code Quality: By enforcing coding standards and best practices, linters help maintain a consistent codebase, making it easier to read, maintain, and collaborate on.
• Customization: Most linters can be customized to suit the specific needs of a project or team. This includes setting rules, configuring severity levels for different types of issues, and integrating with development environments.
• Automation: Linters can be integrated into development workflows, such as continuous integration (CI) pipelines, to automatically check code for issues as it is written or before it is merged into the main codebase.

3. Types of Linters

• Language-Specific Linters: These are designed for specific programming languages (e.g., ESLint for JavaScript, Pylint for Python, RuboCop for Ruby).
• General-Purpose Linters: These can analyze code written in multiple languages (e.g., SonarQube).
• Specialized Linters: These focus on specific aspects of code, such as security (e.g., Bandit for Python security) or formatting (e.g., Prettier for code formatting).

4. Container Images Linters

In the context of Docker and containerization, linters like Dockle are specialized tools that analyze Docker images to ensure they follow best practices and are secure. These linters check for issues such as:

• Security Vulnerabilities: Identifying known vulnerabilities in the software packages included in the image.
• Configuration Issues: Ensuring the Dockerfile follows best practices for security and efficiency.
• Compliance: Checking that the image meets organizational or industry-specific compliance standards.

Using a container image linter like Dockle helps developers build more secure and robust Docker images, reducing the risk of deploying vulnerable or poorly configured containers.

5. How to install Dockle on ubuntu and how we can run

6. First update your machine then install docker on it, and pull some sample image from docker hub

apt-get update

apt-get install docker.io -y

docker pull ubuntu

7. after that we need to install “Dockle” on our system for that run below command

VERSION=$(
 curl --silent "https://api.github.com/repos/goodwithtech/dockle/releases/latest" | \
 grep '"tag_name":' | \
 sed -E 's/.*"v([^"]+)".*/\1/' \
) && curl -L -o dockle.deb https://github.com/goodwithtech/dockle/releases/download/v${VERSION}/dockle_${VERSION}_Linux-64bit.deb

sudo dpkg -i dockle.deb && rm dockle.deb

8. After that run dockle command to scan ubuntu image as follows

dockle ubuntu

Now you can see the result of your scan and then you can take necessary action accordingly

9. If you want store your output in result format you can do also that Dockle support “Json, Sarif”

docker -f json -o results.json ubuntu

10. If you want read more about Dockle you can read on “Dockle”