Docker on Mac: Solving the CLI Connection Error & Understanding the 64GB VM

The Problem

You open your terminal, ready to hack, and type docker ps or try to start a container. Instead of a list of containers, you get this error:

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

I ran into this recently while setting up my Kali Linux environment on my MacBook Pro M3. I tried to start it like a service (systemctl start docker), but that didn’t work either.

The Explanation: Mac vs. Linux

The confusion comes from how Docker works on different operating systems.

• Linux: Docker runs natively. The Docker daemon interacts directly with the Linux kernel. You can start/stop it as a system service.
• macOS & Windows: Docker cannot run natively because these OSs don’t have the Linux kernel features (cgroups, namespaces) that containers need.

To solve this, Docker Desktop creates a lightweight Linux Virtual Machine (VM) in the background.

• The docker command in your terminal is just a client (remote control).
• It sends commands to the daemon running inside that hidden Linux VM.
• Key Takeaway: If the Docker Desktop app isn’t running, the VM isn’t running, and your terminal has no one to talk to.

The “Scary” 64GB File

While investigating, I found a massive file that looked concerning:

/Users/ranger/Library/Containers/com.docker.docker/Data/vms/0/data/docker.raw

It showed a size of 64GB!

Don’t Panic

I learned that this is a Sparse File.

• 64GB is just the maximum capacity limit set by Docker.
• The actual disk space used is only what you’ve written to it (in my case, about 8GB).
• It grows as you add images/containers but won’t eat 64GB of your drive unless you actually fill it up.

The Solution

Manual Way

You must launch the Docker Desktop application before using the terminal commands.

1. Press Cmd + Space.
2. Type “Docker”.
3. Wait for the whale icon to stop animating.

The “Ranger Way” (Automated)

I didn’t want to manually open the app and wait every time. So, I created a smart alias in my .zshrc that:

1. Launches Docker Desktop.
2. Waits for it to initialize (with a cool countdown).
3. Automatically starts and enters my Kali Linux container.

Add this to your ~/.zshrc:

# Kali Linux Docker Launcher
function kali-up() {
    echo "🚀 Launching Docker Desktop..."
    open -a Docker
    
    echo "⏳ Waiting for Docker to initialize..."
    # Wait loop with visual feedback (max 40s)
    for i in {1..40}; do
        if docker info >/dev/null 2>&1; then
            echo -e "\n✅ Docker is ready!"
            break
        fi
        echo -ne "   $((40-i))s... \r"
        sleep 1
    done

    echo "🐳 Starting Kali Container..."
    # Replace 'kali-mcp' with your container name
    docker start kali-mcp && docker exec -it kali-mcp bash
}

Now, I just type kali-up and I’m in.

Rangers lead the way! 🚀