As soon as you start using Docker, you’ll likely hear about .dockerignore files from many different people, so it’s time to clear the air on what they are and how they can improve your workflow. So what exactly are these mysterious little files? Well, they actually do something pretty simple – they allow you to configure exactly which directories or files within your container are ignored by Docker when images are created or containers are created from an image.
What are .dockerignore files
.Dockerignore files are used to specify which files and directories should be ignored by the Docker build process. This can be useful if you have certain files or directories that you don’t want included in your final image. For example, you might want to exclude sensitive data or unnecessary dependencies. By using .dockerignore files, you can improve your workflow by reducing the size of your images and making them more manageable. You’ll also reduce the time it takes for builds to complete because less is being built.
You can add any number of patterns in a single .dockerignore file, just make sure each pattern is on its own line. And as a last note, .dockerignore files are typically placed at the root level of your project directory so they will apply globally across all Docker commands.
How they help
Instead of including all of these assets in your Dockerfile, you could create a .dockerignore file with all of the folders to exclude from copying. Then when your build is done, those folders will not exist on the filesystem inside your container. For more information about how to write a .dockerignore file for Ruby on Rails applications, check out this blog post
2 things to do immediately after installing docker
- Download a text editor like Sublime Text or Atom.
- In your text editor, create a new file and save it as .dockerignore in the root directory of your project.
- Inside the file, write patterns for any files or directories you want Docker to ignore when building your image.
- For example, you might want to ignore files like .gitignore or Dockerfile.
- By default, Docker will include these files in your image, which can clutter it up and make it difficult to work with.
- The .dockerignore file allows you to keep your image clean and tidy, which makes it more efficient and easier to work with overall. 7. Remember that if you’re working on a collaborative project where someone else is also making changes to the same codebase, then you’ll need to add them to your .dockerignore file so they don’t get accidentally overwritten.
- Now go ahead and take that extra minute to add one of these files! It’ll be worth it!
6 best practices for using Docker
Docker is a great tool for development, but there are a few best practices you should follow to get the most out of it. First, make sure to create a .dockerignore file. This will help improve your workflow by excluding certain files and directories from being built into your Docker image.
Second, be sure to keep your Dockerfile simple. A simple Dockerfile is easier to read and understand, and is less likely to break. Third, use Docker Compose to manage multiple containers. This will help keep your environment consistent and simplify development. Fourth, avoid installing unnecessary packages in your containers. This will keep your images small and easy to deploy. Fifth, tag your images with versions so you can easily roll back changes if necessary.