Docker Service and Command Usage Guide

Published on January 3, 2025

Docker Service and Command Usage Guide

This document explains the differences between system-level Docker (dockerd) and user-level Docker Desktop, and also when to use sudo with Docker commands.

1. Starting Docker Services

System-wide Docker Engine

sudo systemctl start docker

  • Starts the Docker Engine (dockerd) as a system service.

  • Runs with root privileges and affects all users.

  • Commonly used on servers and Linux distributions where Docker Engine is installed directly.

Example:

sudo systemctl start docker
docker ps

User-level Docker Desktop

systemctl --user start docker-desktop

  • Starts Docker Desktop as a user service.

  • Runs inside your user session only.

  • Does not require root to run Docker commands.

Example:

systemctl --user start docker-desktop
docker ps

| Command | Scope | Runs As | Use Case | | --------------------------------------- | ------------ | ------- | -------------------------------- | | sudo systemctl start docker | System-wide | Root | Servers, multi-user environments | | systemctl --user start docker-desktop | User session | User | Development, Docker Desktop |

2. Running Docker Commands

With sudo

sudo docker build -t myapp .

  • Runs the Docker CLI with root privileges.

  • Required if your user is not in the docker group.

  • Example error without sudo:

Got permission denied while trying to connect to the Docker daemon socket

Without sudo

docker build -t myapp .

  • Runs Docker as your regular user.

  • Works if:

    • Your user is added to the docker group:
    sudo usermod -aG docker $USER
    • Or you are using Docker Desktop, which manages permissions automatically.

| Command | Privileges | Requirement | Use Case | | --------------------- | ---------- | -------------------------------- | -------------------------- | | sudo docker build . | Root | No setup | Quick use, but less secure | | docker build . | User | docker group or Docker Desktop | Safer, preferred |

Example Workflow

Using system Docker (dockerd):

# Start Docker Engine (system-wide)
sudo systemctl start docker
# Build image (needs sudo if not in docker group)
sudo docker build -t node-app .

Using Docker Desktop (user session):

# Start Docker Desktop
systemctl --user start docker-desktop
# Build image (no sudo required)
docker build -t node-app .

Summary

  • Use system Docker (dockerd) for servers and production.

  • Use Docker Desktop (user session) for local development.

  • Add your user to the docker group for convenience and security.

  • Prefer running Docker without sudo where possible.

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