Building a Docker environment with Colima

TL;DR

• It is simple to build a Docker environment using Colima, if you cannot use Docker Desktop on macOS.

Background

Docker Desktop has been paid for since March 31, 2022 (However, companies with less than 250 employees, less than $10 million in annual revenue, personal or educational use and non-profit OSS will continue to be free of charge). As a result, the Docker Desktop alternative is now required to use Docker for free on macOS etc.

There are several alternatives to Docker Desktop, such as minikube, Rancher Desktop and Lima, but currently Colima looks to be the best in terms of simplicity of setup.

What is Colima?

Colima (Containers in Lima) is a derivative project of Lima, as suggested by its name, which aims to build a Docker/Kuberbetes environment on macOS with minimal setup.

The mechanism of running Docker with Colima is basically the same as with Docker Desktop. A Docker daemon (dockerd) is started in a Linux VM launched by Colima, and Docker clients on the host can access the Docker daemon via docker.socket which is mounted from VM to the host.

Install

Let's install Colima. Colima supports multiple installation methods including Homebrew, MacPorts and Nix.

% brew install colima  # When installing with Homebrew

If the version information can be obtained with colima version command, the Colima installation is complete.

Colima allows us to choose a runtime. Since we want to use Docker as the runtime, install the Docker client here.

% brew install docker

Colima 101

This section describes the basic usage of Colima. The following information is based on the v0.5.2 version of Colima, so be careful if you have installed a major different version.

You can create a new instance of VM (or specify an existing instance) and start it with the colima start command. For example, the following command creates a new instance specifying the number of CPUs, memory size (GB) and disk size (GB), mounts $HOME/ and starts it. The :w is required to make the volume writable. The name of the instance to be created can be specified with the --profile option (default value is default), and the runtime type can be specified with the --runtime option (default value is docker).

% colima start --cpu 4 --memory 8 --disk 100 --mount $HOME/:w

If the instance is successfully created, the colima list command should show an instance named default and the STATUS should be Running. In this state, the Docker client can communicate with the Docker daemon via docker.sock and Docker is ready to use.

To stop the instance, use the colima stop command. And the instance is automatically stopped when the PC is rebooted. The stopped instance can be restarted by colima start command. If the --profile option is not specified, the default instance is started.

The instance configuration can be updated by colima start --edit command. However, the disk size cannot be changed after the instance is created.

Tips

Insecure registries setting

In Docker Desktop, insecure registries can be configured using the GUI. In Colima, you can configure insecure registries by colima start --edit command. Find the following part in the contents displayed by colima start --edit command and update the docker section according to the EXAMPLE.

# EXAMPLE - add insecure registries
# docker:
#   insecure-registries:
#     - myregistry.com:5000
#     - host.docker.internal:5000
#
# Colima default behaviour: buildkit enabled
# Default: {}
docker: {}

Summary

In this article, I have explained about how to build a Docker environment on macOS using Colima. I think Colima is superior to similar alternatives in terms of simplicity of setup.