Docker Desktop, WSL 2 and Docker Engine on Linux

This lesson covers the platform details that differ between Windows, macOS and Linux and that cause most first-week problems. After it you will be able to choose between Docker Desktop and Docker Engine, configure the WSL 2 backend on Windows, fix the classic "permission denied" error on Linux, and tune Docker Desktop's resource settings.

Docker Desktop vs Docker Engine

Containers need a Linux kernel. On Linux, Docker Engine runs natively as a system service. On Windows and macOS, Docker Desktop starts a small Linux virtual machine, runs the daemon inside it, and forwards the docker CLI, ports and files to that VM so the experience feels native.

| | Docker Engine | Docker Desktop | |---|---|---| | Platforms | Linux only | Windows, macOS, Linux | | Includes | daemon, CLI, Compose and Buildx plugins | Engine plus GUI dashboard, Kubernetes, extensions | | Runs as | systemd service | Application with an embedded VM | | Licence | Free (Apache 2.0) | Free for personal use and small businesses; paid for larger organizations |

For servers and CI runners, install Docker Engine. For a developer laptop on Windows or macOS, install Docker Desktop.

Windows: WSL 2 Backend

Docker Desktop on Windows uses the Windows Subsystem for Linux 2 as its backend. WSL 2 provides a real Linux kernel, which is faster and more compatible than the older Hyper-V backend.

powershell

# Run in an elevated PowerShell, then reboot
wsl --install
wsl --set-default-version 2
wsl --update

After installing Docker Desktop, open Settings > Resources > WSL integration and enable your distribution (for example Ubuntu). The docker command then works from both PowerShell and the WSL shell, and both talk to the same daemon.

Two performance rules matter on Windows:

Keep project files inside the Linux filesystem (\\wsl$\Ubuntu\home\you\project), not on C:\. Bind mounts across the Windows-to-Linux boundary are dramatically slower and break file watchers.
Run your editor's WSL integration (for example VS Code's Remote - WSL) so the terminal, Git and Docker all operate on the same filesystem.

Desktop can also switch to Windows containers from the tray menu, but this course, like most real-world work, uses Linux containers.

macOS: Apple Silicon and File Sharing

On Apple silicon (M-series) the Desktop VM is arm64, so images are pulled as linux/arm64 by default. Most official images publish multi-architecture manifests, so this is transparent. When an image only exists for amd64, request it explicitly and Docker emulates it with Rosetta or QEMU:

bash

docker run --platform linux/amd64 --rm some/amd64-only-image

Emulated containers are slower; prefer native arm64 images when they exist. File sharing uses VirtioFS, the fastest option for bind mounts on macOS.

Linux: Engine Install and the docker Group

The sample code at the top installs Docker Engine from Docker's own apt repository on Ubuntu or Debian, which stays current, unlike the distribution's docker.io package. Fedora and RHEL use dnf with the equivalent repository. After installation:

bash

sudo systemctl enable --now docker   # start on boot
docker ps
# permission denied while trying to connect to the Docker daemon socket

That error means your user cannot access /var/run/docker.sock, which is owned by root:docker. Add yourself to the docker group and start a new login session (or run newgrp docker). Membership in this group is equivalent to root, so grant it deliberately. If you prefer not to, rootless mode (dockerd-rootless-setuptool.sh install) runs the daemon as your own user, with minor limitations such as no ports below 1024 by default.

Docker Desktop Settings Worth Knowing

In the Desktop dashboard, Settings > Resources sets CPU, memory and disk for the VM (on Windows with WSL 2, memory is governed by a .wslconfig file in your user profile instead). Docker Engine exposes daemon.json for options such as the default logging driver, and Kubernetes enables a one-click single-node cluster you will use in the orchestration lesson. Verify everything from a terminal:

bash

docker context ls          # desktop-linux should be marked with *
docker run --rm hello-world
docker compose version

Troubleshooting Checklist

"Cannot connect to the Docker daemon": the daemon is not running. Start Docker Desktop, or on Linux check systemctl status docker.
docker works in PowerShell but not in Ubuntu: enable that distribution under WSL integration.
exec format error: the image architecture does not match the machine; add --platform.

Key Takeaways

Docker Engine runs natively on Linux; Docker Desktop wraps a Linux VM for Windows and macOS and adds a GUI and Kubernetes.
On Windows use the WSL 2 backend and keep code inside the WSL filesystem.
Apple silicon pulls arm64 images by default; use --platform linux/amd64 only when necessary.
On Linux, add your user to the docker group or use rootless mode, and enable the service with systemd.
docker context ls, docker run hello-world and docker compose version confirm a healthy setup.

Next lesson: Images vs Containers — understand the difference between the template and the running instance.