Managing applications across different computers used to be a nightmare because software often works on one machine but fails on another. This “it works on my machine” problem is exactly why learning this is essential for modern developers. Docker Commands allows you to package software into neat containers that run anywhere consistently.
What are Docker Commands?
Before we dive into the extensive list, it is vital to understand what Docker actually does. Imagine you are moving house. Instead of throwing your clothes, books, and kitchenware loosely into a truck, you put them into standardised boxes. Docker containers are those boxes. They hold everything an application needs to run: code, libraries, and settings, so it doesn’t matter if the “truck” is a Windows laptop or a Linux server.
To start interacting with these “boxes”, you need to use the command-line interface (CLI). Even if you prefer graphical tools, knowing this by heart is a superpower for any developer. It allows for automation, faster troubleshooting, and a deeper understanding of how your software lives and breathes.
Initial Setup and Verification
When you first install Docker, you need to ensure the engine is purring like a kitten. You can verify your installation using these foundational commands:
- docker –version: This confirms that the software is installed and tells you which version you are running.
- docker info: This provides a “health check” of your entire Docker environment, showing how many containers are running, paused, or stopped.
- docker help: This is your best friend. It displays a full list with brief descriptions of what each one does.
How to Create and Manage Images with Docker Commands?
In the world of Docker, an “image” is a read-only template. Think of it as a recipe for a cake. You can’t eat the recipe, but you use it to bake the actual cake (the container). Managing these recipes requires a specific set of commands.
How to Get Images
Most people don’t write every image from scratch. They use Docker Hub, a massive library of pre-made images. To bring an image onto your computer, you use the docker pull command. For instance, if you want to run a web server, you might type docker pull nginx.
Once you have downloaded a few, your disc space can fill up quickly. You can see what you have by typing docker images. This acts as your local cheat sheet for all the blueprints currently stored on your machine.
Building Your Own Custom Images
As a creator, you will eventually want to make your own images. This is done using a “Dockerfile”, a simple text file with instructions. The command to turn that text file into a usable image is docker build. Usually, you will use the -t flag to give it a name, like this: docker build -t my-cool-app ..
Running and Operating Containers in Docker Commands
Once you have your image, it is time to start it. This is where the real action happens. Running a container is the most frequent task in any Linux environment.
What is “Docker Run”?
The docker run command is a bit of a multitasker. If you don’t have the image locally, it pulls it; then it creates the container and starts it.
- docker run -d: This runs the container in “detached” mode, meaning it runs in the background so you can keep using your terminal.
- docker run -p 80:80: This maps a port from your computer to the container, allowing you to see your website in a browser.
- docker run –name my_web: This gives your container a friendly name so you don’t have to remember long ID numbers.
Monitoring Your Work
Once containers are running, you need to keep an eye on them. The docker ps command is the primary way to see what is active. However, if a container crashes or you stop it, it won’t show up there. You must use docker ps -a to see a full history of all containers, whether they are running or not.
Docker Commands Cheat Sheet
As you gain experience, you will realise that managing containers is about more than just starting them. You need to enter them, stop them, and sometimes “kill” them if they behave badly. Here is a more detailed cheat sheet for daily operations:
Entering a Running Container
Sometimes you need to go “inside” the box to fix something or check a file. On a Linux system, you use the Docker exec command.
Example: docker exec -it <container_id> /bin/bash
The -it stands for “interactive terminal”, and it drops you right into the container’s command line as if you were logged into a different computer.
Stopping and Removing
When you are finished with your work, you should tidy up.
- docker stop: Sends a “polite” request to the container to save its work and shut down.
- docker kill: Forces the container to shut down immediately (the “unplug the power” method).
- docker rm: Deletes the container entirely. Note that you cannot remove a container while it is still running!
Networks and Volumes
To become a true pro, you must understand how containers talk to each other and how they save data. Without these, your data would disappear every time you stopped a container.
Persistent Data with Volumes
Since containers are temporary, we use “Volumes” to store data like databases or user uploads.
- docker volume create: Makes a permanent storage spot on your hard drive.
- docker volume ls: Lists all the storage spots you have created.
- docker volume inspect: Shows you exactly where the files are stored on your linux host.
Connecting Containers via Networks
By default, Docker containers are isolated. If you want your “Web App” container to talk to your “Database” container, they need to be on the same network.
- docker network create: Sets up a private communication line.
- docker network connect: Links an existing container to a network.
How to Clean Docker Commands Linux Environment?
Docker is very efficient, but it can be a bit of a “hoarder”. It keeps old images, stopped containers, and unused networks even when you don’t need them anymore. If your computer starts running slowly or you run out of disc space, it is time for a deep clean.
The most powerful tool in your is Docker system prune. When you run this, Docker will ask, “Are you sure you want to remove all unused data?” If you say yes, it will wipe away every stopped container and dangling image, often freeing up gigabytes of space.
For a more surgical approach, you can use:
- docker container prune: Deletes only the stopped containers.
- docker image prune: Deletes only the images that aren’t being used.
FAQs
What are the most important commands to learn first?
The “Big Three” commands for any beginner are docker run (to start), docker ps (to see what is running), and docker stop (to shut things down).
How can I see a full Docker commands list on my computer?
Simply type docker help in your terminal. This will display all available commands along with a short explanation of their functions.
Is there a Docker Commands cheat sheet PDF for networking?
Yes, for networking, you should focus on docker network ls, docker network create, and docker network connect. These allow containers to communicate securely on your Linux host.
Why should I use a cheat sheet PDF?
A cheat sheet pdf is helpful because it provides a quick physical or digital reference that prevents you from having to search the internet every time you forget a specific flag or syntax.
How do I delete all containers using on Linux?
To remove all stopped containers at once, use the command docker container prune. If you want to delete everything (images, networks, and containers), use docker system prune.
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