What is Docker?

From Shipping Containers to Software Containers

Docker is a revolutionary technology that has completely changed the way software is developed, shipped, and deployed. If you want to become a DevOps engineer or stay relevant in modern software engineering, learning Docker is essential.

But what exactly is Docker, and why is it called “Docker”?
To understand that, we need to take a quick journey back into the history of the shipping industry.

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Before the Shipping Container Revolution

The Chaos Before the 1950s

Before the 1950s, loading and unloading cargo from ships was extremely slow, difficult, and expensive.

Ships carried goods in:

• Wooden boxes

• Barrels

• Sacks

• Nets and odd-shaped bags

Everything had different shapes and sizes, so:

• Hundreds of workers were needed to load/unload

• The cargo often got damaged

• Ships wasted a lot of space

• The process was slow and inefficient

Major Problems

• Slow loading/unloading

• Expensive due to huge labor costs

• Damage and loss of goods

• Inefficient space usage

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1950: The Birth of the Shipping Container

In 1956, American entrepreneur Malcolm McLean introduced the modern shipping container.

These containers were:

• Standard-sized (usually 8 ft or 20 ft long)

• Strong & secure

• Easy to move using cranes

• Stackable

Benefits of Containers

• Fast loading/unloading

• Cheap due to less manpower

• Safe, with reduced damage and theft

• Organized, because every mode of transport used the same standard size

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Why the Name “Docker”?

The word Docker comes from “dock,” referring to a port or harbor.

A Docker (person) is someone who loads/unloads containers at a harbor.
In American English, these workers are also called:

• Longshoremen

• Stevedores

So just like real dockers handle shipping containers, the Docker technology handles software containers.

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Software Before Docker: The Same Chaos

Even in software development, before around 2010, the same “pre-container” problems existed.

Common Issues

1. Version Conflicts

Example:

• Your PC: Python 1.2

• Friend’s PC: Python 3.1

• App works on your machine, but not theirs

2. OS Compatibility Issues

• Works on Windows

• Doesn’t work on Linux or Mac

3. Deployment Problems

The famous line:
“It works on my machine!”

Developers, managers, and servers all had different environments.

This costs companies time, money, and frustration.

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Solomon Hykes and the Birth of Docker

2010: dotCloud

Solomon Hykes founded a company named dotCloud and built an internal tool to solve deployment issues.

2013: The Five-Minute Revolution

During a 2013 conference, Solomon got only five minutes to demonstrate his tool.

Those five minutes changed the software world.

He open-sourced the tool and named it:

Docker

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Docker: Platform or Tool?

Docker is not just a single tool; it is an entire platform built around three main concepts:

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1. Containers

A container packages everything needed for an application:

• Required OS libraries

• Application code

• Dependencies

Just like a shipping container can hold anything, a Docker container holds your entire software environment.

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2. Images

An image is like a snapshot of a container.
You can:

• Share it

• Version it

• Recreate the same environment anywhere

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3. Docker Platform

The Docker platform:

• Loads containers

• Runs containers

• Distributes containers across machines

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How Docker Solves Real-World Problems

Problem: Version Conflicts

Before:

• Python 1.2 and 3.1 can’t run together

With Docker:

• Two containers

• Each container has its own Python version

• Both run on the same machine, no conflict

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Problem: “Works on My Machine”

Before:

• Works on Windows PC

• Fails on Linux server

With Docker:

• Package the app inside a container

• Build an image

• Run the same container anywhere: Windows, Linux, or Mac

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Typical Workflow

1. Develop inside a container

2. Create an image

3. Share with your team or server

4. Deploy the image anywhere

5. Guaranteed identical behavior

No more surprises.

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Docker Logo: The Whale and Containers

Docker’s logo shows:

• A whale

• Carrying stacked containers

Symbolism:

• Whale = Powerful platform

• Containers = Software payloads

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Why Docker is So Important

Global Adoption

• Used by nearly every tech company

• Google, Apple, Microsoft, Amazon—all use Docker

• Every cloud provider supports Docker

Kubernetes Exists Because of Docker

In 2014, Google launched Kubernetes, a system to orchestrate Docker containers.

Without Docker:

• Kubernetes wouldn’t exist

• ChatGPT wouldn’t scale

• YouTube couldn’t handle its traffic

• Modern cloud computing would be impossible

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From dotCloud to Docker Inc.

Docker became so popular that Solomon Hykes renamed his company to Docker Inc., replacing the dotCloud brand entirely.

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Career Benefits of Learning Docker

For DevOps Engineers

• Absolutely essential

• No alternative technology offers the same influence

For Software Engineers

• Helps build advanced, environment-free applications

• Improves understanding of infrastructure

Salary Impact

Docker skills can significantly boost your salary.
For example:
A developer earning 30,000 BDT could reach 45,000 BDT due to Docker expertise alone.

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Final Words

Docker is not just another tool—it is the container revolution for the software industry.

Just as shipping containers reshaped global trade in the 1950s, Docker reshaped software development in 2013.

Docker’s Core Strengths

• Consistency: Same behavior everywhere

• Isolation: No conflicts

• Speed: Faster development and deployment

• Efficiency: Optimal resource use

If you want to build a career in modern software engineering or DevOps, Docker is a must-have skill.
It is the key to entering today’s technology ecosystem.

Because now, the excuse
“It works on my machine.”
no longer works.