Installing Docker - Visual Walkthrough

Process Flow - Installing Docker

Start

↓

Update package info

↓

Install prerequisites

↓

Add Docker repository

↓

Install Docker Engine

↓

Start and enable Docker service

↓

Verify Docker installation

↓

End

This flow shows the step-by-step process to install Docker on a Linux system, from updating packages to verifying the installation.

Execution Sample

Docker

sudo apt update
sudo apt install ca-certificates curl gnupg
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu $(. /etc/os-release && echo \"$VERSION_CODENAME\") stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
sudo systemctl start docker
sudo systemctl enable docker
sudo docker run hello-world

This code installs Docker on Ubuntu, starts the Docker service, enables it on boot, and runs a test container.

Process Table

Step	Command	Action	Result	Notes
1	sudo apt update	Update package lists	Package info refreshed	Prepares system for new installs
2	sudo apt install ca-certificates curl gnupg	Install prerequisites	Prerequisites installed	Needed for secure downloads
3	sudo mkdir -p /etc/apt/keyrings	Create keyrings directory	Directory created	Stores Docker GPG key
4	curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg	Download and save Docker GPG key	Key saved securely	Ensures package authenticity
5	echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu $(. /etc/os-release && echo \"$VERSION_CODENAME\") stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null	Add Docker repository	Repository added	Enables apt to access Docker packages
6	sudo apt update	Update package lists with Docker repo	Package info refreshed with Docker repo	Includes Docker packages
7	sudo apt install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin	Install Docker Engine and tools	Docker installed	Core Docker components ready
8	sudo systemctl start docker	Start Docker service	Docker service running	Docker daemon active
9	sudo systemctl enable docker	Enable Docker on boot	Docker service enabled	Starts automatically on reboot
10	sudo docker run hello-world	Run test Docker container	Hello from Docker! message	Confirms Docker works
11	-	End	Installation complete	Docker ready to use

💡 Docker installed, service running, and test container executed successfully

Status Tracker

Variable	Start	After Step 1	After Step 6	After Step 7	After Step 8	After Step 10
Package Info	Old	Updated	Updated with Docker repo	Same	Same	Same
Docker Service	Stopped	Stopped	Stopped	Stopped	Running	Running
Docker Installation	Not installed	Not installed	Not installed	Installed	Installed	Installed
Test Container Output	None	None	None	None	None	"Hello from Docker!"

Key Moments - 3 Insights

Why do we run 'sudo apt update' twice?

The first 'apt update' refreshes package info before installing prerequisites. The second updates package info again after adding Docker's repository to include Docker packages, as shown in execution_table steps 1 and 6.

What does 'sudo systemctl enable docker' do compared to 'start'?

'start' runs Docker immediately (step 8), while 'enable' makes Docker start automatically on system boot (step 9), ensuring Docker runs after reboot.

How do we know Docker installed correctly?

Running 'sudo docker run hello-world' (step 10) outputs a confirmation message 'Hello from Docker!', proving Docker can run containers.

Visual Quiz - 3 Questions

Look at the execution_table at step 7. What is installed at this step?

A Only Docker CLI

B Docker Engine and related tools

C Docker service started

D Test container run

💡 Hint

Check the 'Action' and 'Result' columns at step 7 in execution_table.

At which step does the Docker service start running?

A Step 8

B Step 6

C Step 9

D Step 10

💡 Hint

Look at the 'Docker Service' variable in variable_tracker after each step.

If we skip step 4 (adding Docker GPG key), what will likely happen?

A Docker packages will install without issues

B Docker service will start but not run containers

C Package authenticity cannot be verified, install may fail

D Test container will run but show warnings

💡 Hint

Step 4 ensures package authenticity; missing it affects package installation security.

Concept Snapshot

Installing Docker on Ubuntu:
1. Update package info (apt update)
2. Install prerequisites (ca-certificates, curl, gnupg)
3. Add Docker GPG key and repo
4. Update package info again
5. Install Docker Engine and tools
6. Start and enable Docker service
7. Run 'hello-world' container to verify
Key: Run 'apt update' after adding repo to get Docker packages.

Full Transcript

To install Docker, first update your system's package list. Then install necessary tools like curl and gnupg to securely download Docker's GPG key. Create a directory to store this key and add Docker's official GPG key to your system. Update your package list again to include Docker's repository. Next, install Docker Engine and related tools. Start the Docker service and enable it to run on boot. Finally, run a test container 'hello-world' to confirm Docker is installed and working correctly.

Practice

1. What is the main purpose of installing Docker on your computer?

easy

A. To create spreadsheets

B. To edit text files

C. To run applications inside containers

D. To browse the internet

Solution

1. Step 1: Understand Docker's role

   Docker is a tool that allows running applications inside isolated containers.

2. Step 2: Compare options

   Only To run applications inside containers describes running apps in containers, which is Docker's main use.

3. Final Answer:

   To run applications inside containers -> Option C

4. Quick Check:

   Docker runs apps in containers = D [OK]

Hint: Docker runs apps in containers, not for editing or browsing [OK]

Common Mistakes:

• Confusing Docker with text editors or browsers
• Thinking Docker is for general software installation
• Assuming Docker manages spreadsheets

2. Which command correctly checks the installed Docker version after installation?

easy

A. version docker --check

B. docker version check

C. check docker version

D. docker --version

Solution

1. Step 1: Recall Docker version command syntax

   The correct command to check Docker version is docker --version.

2. Step 2: Eliminate incorrect syntax

   Other options do not follow Docker CLI syntax and will cause errors.

3. Final Answer:

   docker --version -> Option D

4. Quick Check:

   Correct Docker version command = A [OK]

Hint: Use 'docker --version' to check Docker version quickly [OK]

Common Mistakes:

• Using incorrect command order or words
• Omitting double dashes before 'version'
• Trying non-Docker commands to check version

3. After running docker --version, you see this output:

Docker version 24.0.2, build cb74dfc

What does this output tell you?

medium

A. Docker is installed and working

B. Docker is not installed

C. Docker installation failed

D. Docker needs to be updated

Solution

1. Step 1: Interpret the version output

   The output shows Docker's version number and build info, meaning Docker is installed.

2. Step 2: Understand what output means

   If Docker was not installed or failed, the command would error or show no version.

3. Final Answer:

   Docker is installed and working -> Option A

4. Quick Check:

   Version output means Docker works = C [OK]

Hint: Version output means Docker installed correctly [OK]

Common Mistakes:

• Thinking version output means failure
• Confusing version info with error messages
• Assuming update needed without checking latest version

4. You tried to install Docker on Ubuntu with sudo apt install docker but got an error. What is the likely fix?

medium

A. Use sudo apt install docker.io instead

B. Run docker --version again

C. Restart the computer and try again

D. Install Docker using yum command

Solution

1. Step 1: Understand Ubuntu package naming

   On Ubuntu, the Docker package is named docker.io, not just docker.

2. Step 2: Correct the install command

   Using sudo apt install docker.io installs Docker properly on Ubuntu.

3. Final Answer:

   Use sudo apt install docker.io instead -> Option A

4. Quick Check:

   Ubuntu Docker package = docker.io = A [OK]

Hint: Ubuntu Docker package is 'docker.io', not 'docker' [OK]

Common Mistakes:

• Trying to install 'docker' package which doesn't exist
• Using wrong package manager commands
• Ignoring error messages without checking package name

5. You want to install Docker on Windows using the official installer. Which step should you do first?

medium

A. Run sudo apt install docker in PowerShell

B. Download Docker Desktop from the official Docker website

C. Open Command Prompt and type docker run

D. Install VirtualBox before Docker

Solution

1. Step 1: Identify Windows installation method

   Windows users install Docker using Docker Desktop downloaded from Docker's official site.

2. Step 2: Eliminate incorrect steps

   Linux commands like sudo apt install don't work on Windows; VirtualBox is not required.

3. Final Answer:

   Download Docker Desktop from the official Docker website -> Option B

4. Quick Check:

   Windows Docker install starts with official Docker Desktop download = B [OK]

Hint: Windows Docker install starts with official Docker Desktop download [OK]

Common Mistakes:

• Trying Linux commands on Windows
• Assuming VirtualBox is needed for Docker
• Running Docker commands before installation