Skip to content

Docker Installation and Setup

Overview

Install a working Docker Engine (or Desktop), verify with docker version / hello-world, and know when rootless Docker and contexts matter.

Docker Engine on Linux is the production-like path. Docker Desktop bundles Engine + UI on macOS/Windows. Rootless reduces privilege; contexts point the CLI at remote engines.

This is a core tutorial in Module 2 · Installing Docker of the REBASH Academy Docker for Cloud & DevOps Engineers series — written for Cloud, DevOps, Platform, and SRE engineers.

Prerequisites

Learning Objectives

By the end of this tutorial, you will be able to:

  • Install Engine or Desktop for your OS
  • Confirm daemon is running
  • Run hello-world
  • List Docker contexts
  • State rootless trade-offs

Architecture

This topic’s control points and relationships are shown below.

Docker architecture

Theory

What

You can run containers with Docker Engine on Linux servers, Docker Desktop on macOS/Windows, or rootless Engine variants that reduce host privilege. The CLI can target different engines via contexts. Post-install group membership on Linux (docker group) controls who may talk to the daemon socket.

Why

Dev/prod parity suffers when laptops use Desktop’s virtual machine networking while CI uses Engine on Linux. Security-sensitive environments prefer rootless or restricted access because membership of the docker group is effectively root via the socket. Choosing the right install path early avoids “it works locally” surprises.

How it works

On Linux servers and CI runners, install Engine from the vendor repository, start the systemd unit, and verify with docker version / docker info. On macOS/Windows, Desktop runs a Linux virtual machine that hosts the engine. Rootless mode runs the daemon as your user with networking trade-offs. Contexts switch the CLI between local Desktop, a remote TCP endpoint, or another node. After adding a user to the docker group, a full logout/login is required for group membership to apply.

Option When
Engine (Linux) Servers, CI runners, closest to production
Desktop Local macOS/Windows development
Rootless Security-sensitive laptops (limits apply)
Context Point CLI at remote/dev VM

Key concepts

  • Socket permissions — who can control the daemon
  • Desktop VM — extra network/filesystem translation layer
  • Credential helpers — registry login storage
  • Version skew — keep CLI and Engine reasonably aligned

Common pitfalls

  • Using sudo docker forever instead of fixing group membership (or vice versa, granting it too widely)
  • Exposing dockerd on TCP 0.0.0.0 without mutual TLS
  • Assuming Desktop file mounts behave like Linux bind mounts in production
  • Skipping docker info after install and missing cgroup or storage-driver issues

Hands-on Lab

Create a workspace for this tutorial.

mkdir -p ~/rebash-docker/module-02 && cd ~/rebash-docker/module-02

Focus: verify Docker Engine install and daemon connectivity

Step 1 – Daemon and client checks

docker version
docker info --format '{{.ServerVersion}} {{.Driver}}'
docker pull alpine:3.20
docker run --rm alpine:3.20 uname -a

Step 2 – Permission / context notes

docker context ls
id
cat > install-notes.md << 'EOF'
- Prefer Docker Engine from official docs for your OS
- docker group is root-equivalent — grant carefully
- Consider rootless mode when isolation requires it
EOF

Final step – Cleanup note

docker rmi alpine:3.20 2>/dev/null || true
# Keep ~/rebash-docker/ for later tutorials

Validation

  • Lab commands run under ~/rebash-docker/module-02/
  • You can explain each Theory section in your own words
  • You used modern tooling where it applies to this topic
  • You can describe one production failure mode for this topic

Code Walkthrough

Production practice for Docker Installation and Setup always combines:

  1. Inspect before you change (status, plan, logs, dry-run)
  2. Prefer reversible, documented changes (Git, IaC, drop-ins, version pins)
  3. Capture evidence (command output, pipeline logs) for handovers
  4. Prefer current tools and APIs over legacy shortcuts
  5. Least privilege — escalate credentials only when required

Keep runbooks short enough to follow under pressure. Automate checks; keep humans for judgement.

Security Considerations

  • Treat credentials and tokens for docker as privileged — never commit them
  • Prefer short-lived auth (OIDC, roles, SSO) over long-lived keys
  • Validate blast radius before apply/deploy/delete operations
  • Restrict who can approve production changes
  • Collect audit logs; limit who can read sensitive traces

Common Mistakes

Using sudo docker forever instead of fixing group membership (or vice versa, granting it

Validate assumptions against the Theory section and official docs before changing production.

Exposing dockerd on TCP 0.0.0.0 without mutual TLS

Lab shortcuts (open security groups, admin roles, skip approvals) must not ship unchanged.

Changing production without a rollback path

Always know how to revert (previous artefact, prior release, state rollback, DNS failback).

Best Practices

  • Encode Docker Installation and Setup changes as code and review them in pull requests
  • Pin versions (images, modules, actions, provider plugins)
  • Separate environments with clear promotion gates
  • Alert on symptoms with runbooks attached
  • Destroy lab resources; tag everything with owner and expiry where possible

Troubleshooting

Symptom Likely cause Fix
Auth / permission denied Wrong identity, policy, or scope Check caller identity, roles, and least-privilege policies
Timeout / no route Network, DNS, security group, or endpoint Trace path, DNS, and allow-lists before retrying
Drift / unexpected plan Manual change or wrong state/workspace Reconcile desired vs actual; avoid click-ops on managed resources
Pipeline/job red Flaky step, cache, or missing secret Read failing step logs; bisect recent workflow/config changes
Cost spike Idle load balancer, NAT, oversized compute Inventory billable resources; stop/delete labs promptly

Summary

Docker Installation and Setup is essential for Cloud and DevOps engineers working with docker. Practise the lab until the inspection and change path is muscle memory, then continue the track.

Interview Questions

  1. What does membership in the docker group imply on Linux?
  2. Client works but daemon errors — where do you look?
  3. Rootless Docker — when would you choose it?
  4. How do you verify Engine versus Compose plugin install?
  5. What is a Docker context used for?

Sample answer — question 2

Run docker version/docker info and inspect daemon logs. Permission denied on the socket usually means group/context issues.

Sample answer — question 4

Treat docker.sock access as root-equivalent.

References