Master Docker Installation and Usage on Ubuntu 20.04 with Docker Compose

Introduction

Getting Docker up and running on Ubuntu 20.04 is a game-changer for container-based development. In this guide, we’ll walk you through the entire Docker installation process on Ubuntu, from setting up Docker Engine to managing containers and images. You’ll also learn how to use Docker Compose to streamline multi-container applications, and we’ll cover common troubleshooting tips along the way. Whether you’re new to Docker or just looking to sharpen your skills, this tutorial will equip you with the tools you need to get the most out of Docker on Ubuntu.

Step 1 — Installing Docker

So, you’ve decided to set up Docker on your Ubuntu system! But here’s the thing: the version of Docker you get from the official Ubuntu repository might not always be the latest. To get the freshest version, packed with all the newest features and bug fixes, it’s a good idea to install Docker from the official Docker repository. Don’t worry—I’m going to walk you through it, step by step.

First, let’s make sure your system is up-to-date with the latest packages and updates. You’ll want to run this to update your package list:

$ sudo apt update

Next, you need to install a few packages that will help your system securely fetch packages over HTTPS—super important for adding Docker’s official repository. Run this:

$ sudo apt install apt-transport-https ca-certificates curl software-properties-common

Once those are installed, it’s time to add Docker’s GPG key. This step is a security check, ensuring that the Docker packages you’re downloading are legit and haven’t been tampered with. Here’s how you add the key:

$ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add –

Now, let’s tell your system where to find Docker’s packages. You’ll add Docker’s official repository to your system’s list of sources with this command:

$ sudo add-apt-repository “deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable”

Once you run that command, your system will automatically update its package database to include Docker’s repository. To double-check everything, you can run this command to confirm that your system is ready to install Docker from the Docker repository:

$ apt-cache policy docker-ce

You should see something like this:

docker-ce:
  Installed: (none)
  Candidate: 5:19.03.9~3-0~ubuntu-focal
  Version table:
     5:19.03.9~3-0~ubuntu-focal 500
        500 https://download.docker.com/linux/ubuntu focal/stable amd64 Packages

This means Docker isn’t installed yet, but the package is ready to go. Now, it’s time to install Docker! Just run:

$ sudo apt install docker-ce

Once that’s done, Docker will be installed on your system. The Docker service (also known as the Docker daemon) will automatically start and be set to run every time your system boots up. To check that Docker is up and running, use this command:

$ sudo systemctl status docker

If everything’s working as it should, you should see something like this:

● docker.service – Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
   Active: active (running) since Tue 2020-05-19 17:00:41 UTC; 17s ago
   TriggeredBy: ● docker.socket
   Docs: https://docs.docker.com
   Main PID: 24321 (dockerd)
      Tasks: 8
      Memory: 46.4M
   CGroup: /system.slice/docker.service
           └─24321 /usr/bin/dockerd -H fd:// –containerd=/run/containerd/containerd.sock

And there you go! Docker is installed, the service is running, and you’re all set to start working with containers. Plus, you now have access to the Docker command-line tool (Docker client). In the next sections, we’ll dive deeper into how to use the docker command to manage containers and images.

What is Docker?

Step 2 — Executing the Docker Command Without Sudo (Optional)

Alright, so you’ve installed Docker on your Ubuntu machine, and you’re ready to dive in. But here’s the deal: by default, Docker commands can only be run by the root user or someone who’s part of the special “docker” group. Think of this group as a VIP club that grants you access to Docker’s inner workings.

If you try running a Docker command and you’re not in this club, you’ll probably get an error like this:

docker: Cannot connect to the Docker daemon. Is the docker daemon running on this host? See ‘docker run –help’.

This happens because Docker needs the right permissions to talk to its daemon (that’s the background process running Docker containers), and usually, that means you need root access. So, what can you do? You probably don’t want to type sudo every single time you want to run a Docker command, right? Who could blame you?

Well, there’s a way to fix that! You can add your user to the “docker” group, which gives you the permissions you need to run Docker commands without needing to use sudo all the time. Here’s how you do it:

$ sudo usermod -aG docker ${USER}

This command adds your current user to the Docker group. But, you’re not quite done yet. To make sure the changes take effect, you either need to log out and back in, or you can make the change immediately by running:

$ su – ${USER}

Once you run that, it will ask for your password. After you enter it, you’re all set! To confirm that you’re now in the Docker group, you can run:

$ groups

This will give you a list of groups your user belongs to. You should see docker listed there, like this:

sammy sudo docker

Now, your user has the power to run Docker commands without having to type sudo every time.

$ sudo usermod -aG docker username

And that’s it! From now on, we’ll assume you’re running Docker commands as a member of the Docker group. But hey, if you prefer to stick with using sudo for each command, that’s fine too. Either way, the next step is the fun part: using the Docker command! Let’s dive into what you can do with it.

Docker Containers Overview

Step 3 — Using the Docker Command

So, you’ve got Docker up and running on your Ubuntu machine, and now it’s time to start using it. You’re all set to jump into Docker commands, but first, let’s talk about how they work. Here’s the thing: Docker commands follow a specific format. Think of it like giving directions to your car’s GPS—you need to tell it exactly where to go, and in Docker’s case, where to act, what to do, and with which items.

The general format for running a Docker command looks like this:

docker [option] [command] [arguments]

Each part of this structure plays its own role. The option fine-tunes your command, the command is the action you want Docker to perform, and the arguments specify the details. Pretty straightforward, right?

Now, you might be wondering, “What commands can I actually use?” Well, with Docker version 19 (and beyond), you’ve got a whole range of commands available. Each one lets you interact with Docker containers and images in different ways. Let’s break down some of the key subcommands you’ll be using most often:

• attach: This one lets you attach your local standard input, output, and error streams to a running container. It’s like tuning in to your container’s live feed.
• build: Need to build a new image from a Dockerfile? This is your go-to command. Think of it as the “construction worker” of Docker.
• commit: Made some changes to a container? You can commit those changes into a brand-new image.
• cp: Need to copy files or folders between your container and your local system? This is like your file-sharing tool for Docker.
• create: Ready to spin up a fresh container? Use this command to create one from scratch.
• exec: Sometimes, you need to run a command inside a running container. This command is like giving a task to a robot that’s already walking around.
• export: This lets you export a container’s entire filesystem into a tar archive. It’s like packaging up your container for easy sharing.
• images: Want to list all the images you have on your system? This command shows you your gallery of Docker creations.
• logs: Need to check what’s happening inside a container? This command fetches the logs so you can see exactly what’s going on under the hood.

And that’s just the start! There are many more commands to explore. For example,

docker ps

docker pull

docker push

Let’s say you’re curious about the available options for a specific command. No problem! You can always check out the available options with the --help flag. For example:

docker run –help

And if you want a peek at some system-wide information about your Docker setup, try running:

docker info

This will give you cool details, like your Docker version, storage drivers, and which containers are running.

Now that we’ve covered the basics of Docker commands, let’s dive deeper into some of the most important ones—like how to work with Docker images. You’ll be using images all the time, as they form the foundation of Docker’s containerized world. Ready to dive in? Let’s go!

Docker Overview and Resources

Step 4 — Working with Docker Images

Imagine you’re about to start a project, and you’ve got all the materials you need laid out in front of you. But here’s the twist—these materials aren’t sitting on a table; they’re ready to be assembled into a custom creation on your machine. That’s what Docker images are to Docker containers. These images are like blueprints for your containers, the base materials that bring your project to life.

By default, Docker pulls these images from Docker Hub, a massive online library of ready-made blueprints maintained by Docker itself. Think of Docker Hub as a giant warehouse, filled with pre-built images for all sorts of applications and Linux distributions. The best part? It’s not just Docker’s own stuff; anyone can contribute their creations. So, whether you’re looking for an image for Ubuntu, Node.js, or a custom setup, chances are, you’ll find it there.

Now, let’s see if your Docker setup is actually working. You know, you’ve done the installation and everything, but how do you know it’s ready to roll? Here’s a fun little trick. Run this command:

$ docker run hello-world

Docker will go on a small adventure, searching for the “hello-world” image on your system. If it doesn’t find it, it’ll pull it straight from Docker Hub. You’ll see something like this:

Unable to find image ‘hello-world:latest’ locally
latest: Pulling from library/hello-world
0e03bdcc26d7: Pull complete
Digest: sha256:6a65f928fb91fcfbc963f7aa6d57c8eeb426ad9a20c7ee045538ef34847f44f1
Status: Downloaded newer image for hello-world:latest
Hello from Docker!

What just happened here? Docker couldn’t find the image locally, so it fetched it from Docker Hub, then created a container from it. The “Hello from Docker!” message means your system is all set up and ready to work with containers.

Now, let’s say you want to look for something more than just the hello-world image. You can use the docker search command to dig through the Docker Hub catalog. For example, if you’re after an official Ubuntu image, just type:

$ docker search ubuntu

This will bring back a list of images related to Ubuntu. You’ll see entries like this:

NAME        DESCRIPTION          STARS        OFFICIAL        AUTOMATED
ubuntu        Ubuntu is a Debian-based Linux operating sys…       10908        [OK]        [Yes]
dorowu/ubuntu-desktop-lxde-vnc      Docker image to provide HTML5 VNC interface …        428        [OK]        [No]
rastasheep/ubuntu-sshd       Dockerized SSH service, built on top of offi…        244        [OK]        [No]

The [OK] in the “OFFICIAL” column means that the image is official, so you can trust that it’s maintained by the organization behind Ubuntu itself. If you find the image you want, you can grab it by running:

$ docker pull ubuntu

Docker will fetch the Ubuntu image, and you’ll see something like this:

Using default tag: latest
latest: Pulling from library/ubuntu
d51af753c3d3: Pull complete
fc878cd0a91c: Pull complete
6154df8ff988: Pull complete
fee5db0ff82f: Pull complete
Digest: sha256:747d2dbbaaee995098c9792d99bd333c6783ce56150d1b11e333bbceed5c54d7
Status: Downloaded newer image for ubuntu:latest
docker.io/library/ubuntu:latest

Once Docker has pulled the image, you’re ready to roll! You can use this image to create a container. If you’re wondering what images you’ve already downloaded, just run:

$ docker images

The output will show you a list of images, like this:

REPOSITORY        TAG        IMAGE ID        CREATED        SIZE
ubuntu        latest        1d622ef86b13        3 weeks ago        73.9MB
hello-world        latest        bf756fb1ae65        4 months ago        13.3kB

Here, you can see both the ubuntu and hello-world images, along with other useful details like the image ID, creation time, and size.

So, what can you do next? Well, Docker isn’t just for reading and pulling images. It’s all about getting creative. You can modify these images, install new software, or tweak configurations. When you’re done making changes, you can save your modified container as a new image.

This new image can be shared with the world, or just kept for your own use, by pushing it to Docker Hub or another registry. But we’ll dive into how to do that in the next section. For now, focus on getting comfortable with Docker images—after all, they’re the foundation for everything you’ll do with Docker containers!

Step 5 — Running a Docker Container

Picture this: you’ve just run the hello-world container, and while it did its job by showing you a simple “Hello from Docker!” message, it didn’t really do much else. But here’s the thing—Docker containers can do a lot more than just display a test message. They’re like portable, lightweight virtual machines that can handle all sorts of tasks. The best part? They don’t use nearly as many resources as a full virtual machine would.

Now, let’s step things up a bit. Instead of just running a basic test container, let’s run something more practical using the latest Ubuntu image. The beauty of Docker is that you can turn this image into a container and interact with it just like you would with a normal machine.

To do this, you’ll need to add a couple of flags to the docker run command. The -i flag stands for “interactive mode,” which keeps the container running, and the -t flag gives you a terminal (or pseudo-TTY). This setup lets you get inside the container’s shell and make changes just like you’re logged into a regular system. The command will look like this:

$ docker run -it ubuntu

Once you run that command, your terminal prompt will change. You’ll notice something different—it’ll look like you’ve logged into a system, but in reality, you’re inside the container. You’ll see something like this:

root@d9b100f2f636:/#

That number, d9b100f2f636 , is the container ID. It’s really important because, when you need to stop, remove, or do anything else with the container, you’ll refer to it by that ID.

Now that you’re inside, you can start working! You can run any command you’d normally use on a Linux machine. For example, let’s say you want to update the system inside your container. Since you’re logged in as the root user, there’s no need for sudo . Just type:

apt update

The system will fetch the latest updates, and then you can install whatever you need. For this example, let’s install Node.js. You’ll do it like this:

apt install nodejs

Once Node.js is installed, check if everything’s working by verifying the installed version with:

node -v

If everything goes smoothly, you’ll see something like this:

v10.19.0

Now here’s a fun fact: any changes you make inside the container—like installing Node.js or adding a new app—only affect that container. They don’t touch your host machine or any other containers. It’s like having a mini, self-contained environment where you can experiment without messing up the main system.

When you’re done, you can exit the container and return to your regular host terminal by typing:

exit

And just like that, you’re back to your regular command line.

In the next part of this tutorial, we’ll dive deeper into managing Docker containers—like how to list, stop, and remove them. So, stay tuned!

What is a Docker Container?

Step 6 — Managing Docker Containers

So, you’ve started using Docker, and now your system has containers everywhere—some are running, some are inactive, and maybe a few are just hanging around. The thing is, managing these containers efficiently is super important if you want to keep things organized and make sure your Docker environment stays smooth. Think of it like having a digital closet—you don’t want it to get too cluttered!

To get started, let’s take a look at the active containers. Just type in:

$ docker ps

This command shows you all the containers that are currently running. When you run it, you’ll see something like this:

CONTAINER ID    IMAGE      COMMAND      CREATED

For example, in our tutorial, we started two containers: one from the hello-world image and another from the ubuntu image. While these containers might not be running anymore, they’re still hanging around in your system, just waiting to be managed.

If you want to see everything, not just the ones running, use this command to view both active and inactive containers:

$ docker ps -a

The output will look something like this:

1c08a7a0d0e4  ubuntu      ”/bin/bash”    2 minutes ago    Exited (0)  8 seconds ago  quizzical_mcnulty

a707221a5f6c  hello-world      ”/hello”    6 minutes ago    Exited (0)  6 minutes ago  youngful_curie

As you can see, the container IDs, images used to create them, commands executed, and their current status are all listed. You can easily tell what’s going on.

But what if you just want to know about the most recent container you created? Well, you can add the -l flag to focus on the latest one:

$ docker ps -l

The output will show you exactly the details of the newest container:

CONTAINER ID    IMAGE      COMMAND      CREATED      STATUS      PORTS      NAMES

1c08a7a0d0e4  ubuntu      ”/bin/bash”    2 minutes ago    Exited (0)    40 seconds ago  quizzical_mcnulty

Okay, now that you’ve seen what’s going on, what if you want to bring a stopped container back to life? Simple! Just use the

docker start

$ docker start 1c08a7a0d0e4

After you start it, check the status again using

docker ps

$ docker ps

Now, to stop a running container, you simply use

docker stop

$ docker stop quizzical_mcnulty

Once the container is stopped and you’re sure you won’t need it again, you can remove it from your system entirely using:

$ docker rm youngful_curie

This will delete the container. Poof! Gone.

But wait, what if you want to get fancy and create a container with a specific name? Well, with Docker, you can do that too. Here’s how:

$ docker run –name my-container ubuntu

Now, you’ve created a container from the ubuntu image, and you’ve given it the name my-container . Fancy, right?

And just when you thought things couldn’t get any better, Docker lets you automatically remove containers once they stop. You don’t have to worry about old containers cluttering up your system anymore. Simply add the --rm switch when running a new container:

$ docker run –rm ubuntu

When that container stops, it’ll delete itself. No mess, no fuss.

If you want to dive deeper into these options and discover even more flags, use this handy command to see what else Docker has to offer:

$ docker run –help

Finally, here’s a little secret: you can take a container and turn it into a new image. That’s right—any changes you make inside the container can be saved and reused in future containers. This lets you create your own customized base images. Pretty cool, huh? But we’ll get into that in the next section of the tutorial. Stay tuned!

Step 7 — Committing Changes in a Container to a Docker Image

Imagine you’ve set up a Docker container, maybe from a simple Ubuntu image, and you’ve started installing some software, like Node.js. You’re feeling pretty good about it, right? But here’s the thing—those changes are only inside that container. Once you stop and remove the container, all your hard work gets wiped out. All that precious Node.js you installed? Gone. Poof.

But don’t worry, there’s a way to save all those changes! You can commit the changes to a new Docker image. Think of it like making a snapshot of your container—like saving your progress in a game so you can come back to it later or share it with friends.

For example, let’s say after installing Node.js inside your Ubuntu container, you want to save the updated state, so you can use it again or share it with others. That’s where committing comes in. With Docker, you can turn your container into a new image that reflects all the changes you’ve made.

Here’s how you do it. You’ll use this command:

$ docker commit -m “What you did to the image” -a “Author Name” container_id repository/new_image_name

Let’s break that down:

• -m : This is where you add a commit message. It’s like writing a note to yourself saying, “Hey, I installed Node.js in this container!”
• -a : This is where you specify the author of the changes. You can put your name here, so everyone knows who made the changes.
• container_id : Remember that ID you saw when you started the container? That’s what you’ll use here.
• repository/new_image_name : This is the name of the new image. If you haven’t created a repository on Docker Hub, it’ll usually default to your Docker Hub username.

Let’s say your username is sammy, and the container ID is d9b100f2f636. To save the container’s updated state (with Node.js installed), you’d type:

$ docker commit -m “added Node.js” -a “sammy” d9b100f2f636 sammy/ubuntu-nodejs

Once you run this command, voila! A new image is created and saved locally on your system. It contains everything you’ve done inside the container, like the Node.js installation.

Now, you might be wondering, “Did it work?” Well, you can check by listing all the images on your system. Just run:

$ docker images

The output will look something like this:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
sammy/ubuntu-nodejs  latest              7c1f35226ca6        7 seconds ago       179MB
ubuntu              latest              1d622ef86b13        3 weeks ago         73.9MB

In this example, the sammy/ubuntu-nodejs image is the new one you just created, derived from the official Ubuntu image. You’ll notice the size is a bit bigger because it includes all the changes you made, like the Node.js installation.

So, next time you need to spin up a container with Ubuntu and Node.js already installed, you don’t need to go through the whole installation process again. You can simply use the sammy/ubuntu-nodejs image. Neat, right?

If you want to take it a step further, you can automate this whole process using a Dockerfile. This lets you automatically install software and customize images without having to manually install anything. But that’s a topic for another time.

The next thing you’ll probably want to do is share this new image with others. After all, you’ve created something useful, and now it’s time for others to benefit. That’s where pushing the image to a Docker registry, like Docker Hub, comes in. But we’ll get to that in the next section. Stay tuned!

What is a Docker Container?

Step 8 — Pushing Docker Images to a Docker Repository

So, you’ve created a shiny new Docker image—congratulations! Now comes the fun part: sharing it with the world, or just with a select few. You can either make it available to the public on Docker Hub or push it to another Docker registry that you have access to. The world is your oyster! But, before we get into it, there’s one important thing to remember—you’ll need an account on the platform where you want to push your image. Once that’s sorted, you’re ready to go.

The first thing you need to do is log into Docker Hub. It’s like unlocking the door to your Docker repository. Use this simple command:

$ docker login -u docker-registry-username

Once you hit enter, Docker will ask for your password. Provide the correct credentials, and boom, you’re authenticated. Now you’re good to push those images to your account.

But wait—there’s a catch. If the username you used to create the image is different from the Docker registry username, you’ll need to tag the image properly. Think of tagging as giving your image the correct name tag at a party—this way, Docker knows exactly where to send it. So, if your registry username is docker-registry-username , and your image is named sammy/ubuntu-nodejs , you would need to run:

$ docker tag sammy/ubuntu-nodejs docker-registry-username/ubuntu-nodejs

This step is key, because it ensures that the image is correctly associated with your account on Docker Hub. Now, you’re all set to send it off. Push the image by running:

$ docker push docker-registry-username/ubuntu-nodejs

In your case, if you’re pushing sammy/ubuntu-nodejs to your Docker Hub repository, you would run:

$ docker push sammy/ubuntu-nodejs

And now, we wait. The image layers need to upload, and depending on how big your image is, this could take a little time. But once it’s done, you’ll see output like this:

The push refers to a repository [docker.io/sammy/ubuntu-nodejs]
e3fbbfb44187: Pushed
5f70bf18a086: Pushed
a3b5c80a4eba: Pushed
7f18b442972b: Pushed
3ce512daaf78: Pushed
7aae4540b42d: Pushed

That’s Docker telling you, “Hey, everything’s been uploaded successfully!” Now, your image is safely stored on Docker Hub and ready for the world—or your team—to use. It’ll show up on your account’s dashboard, just like any other file you might upload to the cloud.

If you hit an error while pushing, don’t panic! Maybe you forgot to log in. If you see something like this:

The push refers to a repository [docker.io/sammy/ubuntu-nodejs]
e3fbbfb44187: Preparing
5f70bf18a086: Preparing
a3b5c80a4eba: Preparing
7f18b442972b: Preparing
3ce512daaf78: Preparing
7aae4540b42d: Waiting
unauthorized: authentication required

This means you weren’t logged in properly. Just run the

$ docker login

Now, your image is officially in Docker Hub! You can verify its existence by checking your account and sharing it with others. If someone else wants to use your image, or if you want to pull it to a new machine, you can simply run:

$ docker pull sammy/ubuntu-nodejs

This will download the image to that machine, and from there, they (or you) can create a container based on your newly uploaded image. And there you have it—a Docker image in the cloud, ready for action. Happy Docker-ing!

Working with Docker Images and Repositories

Docker vs Docker Compose

Imagine you’re building a house, but instead of having one big construction crew, you need to hire several specialized teams. There’s one crew for the foundation (web server), another for the plumbing (database), and another for the wiring (caching layer). Sounds like a logistical nightmare, right? Well, that’s where Docker comes in: it helps you manage those individual teams, or rather, containers. But when it comes to managing all of them together, that’s where Docker Compose comes into play.

Docker is fantastic for building and running individual containers—think of it as your go-to tool for constructing a single part of your house. But let’s face it, when your house has multiple teams working on different sections, managing them all separately can get a bit… well, chaotic. Docker Compose was designed to make life easier when you need to manage multiple containers at once. It takes the headache out of juggling several containers by letting you define and run them with just one configuration file.

Instead of manually starting up separate containers for each service—like your web server, database, and caching system—you can write them all out in a neat and tidy file called docker-compose.yml . Once you’ve got everything set up, all it takes is one simple command to bring everything to life:

$ docker-compose up

That’s it! With a single command, you’ve orchestrated all your services at once, without needing to handle each container individually. Docker Compose allows your containers to work together as a cohesive system, saving you time and effort.

Now, you might be thinking, “This sounds great, but how do I know when to use Docker Compose?” Well, let’s break it down. Docker Compose is perfect for complex applications where you’re dealing with multiple interconnected containers. If you’re testing isolated containers or just working on a small, self-contained app, Docker CLI (the command-line interface) is a perfectly good tool. But as soon as you start needing multiple containers working together, Docker Compose becomes your best friend.

Here’s a quick comparison to help clarify the differences between Docker CLI and Docker Compose:

With Docker CLI, you’re handling each container by itself, which is great for isolated setups. But when you need to orchestrate multiple containers and manage them as part of a bigger picture, Docker Compose steps in to make everything smoother and more manageable, especially in development and testing environments.

If you’re curious to dive deeper into Docker Compose, there are plenty of tutorials out there to guide you. These will take you from the basics—setting up simple applications—to more complex configurations where Docker Compose really shines. It’s a game-changer for developers who want to streamline their workflows and manage multiple containers without the hassle.

So, whether you’re just getting started with Docker or you’re diving into a complex multi-container project, Docker Compose is definitely worth checking out!

Troubleshooting Common Docker Installation Issues

So, you’re all fired up to dive into Docker, right? You’ve got the tools ready, and you’re about to set everything up—but then, boom, you hit a roadblock. Sound familiar? Don’t worry, you’re not alone. It’s pretty common to face a few bumps when setting up Docker, especially for the first time. But no need to stress! Here’s a story of some of the most common hiccups you might encounter, along with the fixes that’ll help you get back on track.

Problem: “docker: command not found”

You’ve typed in docker to run your first command, but instead of Docker jumping into action, you get a cold, empty error that says, “docker: command not found.” You’re probably thinking, “What gives?” Well, the reason behind this is usually a simple one: Docker’s command-line interface (CLI) isn’t included in your system’s $PATH variable. No worries, this is easy to fix. All you need to do is reinstall Docker or make sure the /usr/bin directory is included in your path. Here’s how you can do that:

sudo apt install docker-ce docker-ce-cli containerd.io

This will restore the necessary Docker CLI tools, and voilà! You’ll be able to use the docker command from the terminal without a hitch.

Problem: “Cannot connect to the Docker daemon”

Next, let’s say you’ve managed to install Docker, but you hit another roadblock: “Cannot connect to the Docker daemon.” This can happen for a couple of reasons. Either your Docker daemon (the background service that runs Docker containers) isn’t running, or your user doesn’t have the right permissions to access the Docker service.

But don’t worry—it’s a quick fix. First, make sure the Docker service is running:

sudo systemctl start docker

Then, you need to add your user to the Docker group so you won’t have to type sudo before every Docker command. Run this command:

sudo usermod -aG docker $USER

Once you’ve done that, you’ll need to log out and log back in to apply the changes. After logging back in, you should be good to go, and Docker will recognize you as a user with the right permissions. No more need for sudo —you’re all set to run Docker commands freely!

Problem: GPG Key or Repository Error

Okay, this one’s a bit tricky, but you’ll handle it. Sometimes you might run into a GPG key error or issues with the Docker repository. This usually happens when the key server or the Docker GPG key has changed. No need to panic! Just head over to Docker’s official documentation to get the latest GPG key and repository setup instructions. If you’re using a specific version of Ubuntu, like Ubuntu 22.04, you might need some version-specific tweaks, so make sure to check for those details.

But hey, if you want a smoother, more automated installation process that helps avoid these kinds of errors in the future, why not consider using a tool like Ansible? Ansible lets you automate Docker installations across multiple machines, ensuring consistent configurations and saving you time.

In Conclusion:

So, there you have it! These are the common Docker installation issues you might run into. The good news? Each one has a straightforward fix that’ll help you continue your Docker-based development journey without too much of a detour. Whether you’re just getting started with Docker or running into some snags along the way, you now know exactly what to do to get back on track and keep pushing forward with your Ubuntu Docker setup. Happy containerizing!

Common Docker Installation Issues and How to Fix Them

Docker Desktop on Ubuntu (Beta)

Picture this: you’re a developer, diving into the world of Docker, trying to make sense of containers, images, and networks. Maybe you’re new to it all, or maybe you’re just looking for a smoother, more intuitive way to manage your Docker setup. Well, here’s the thing—Docker Desktop for Ubuntu is here to make your life easier. It’s still in beta, but it already has some awesome features that will definitely help you get more out of Docker.

Imagine having all the tools you need to manage containers, images, volumes, and networks—right at your fingertips, with a clean, graphical user interface (GUI). That’s what Docker Desktop brings to the table. If you prefer a visual interface over typing out endless commands, Docker Desktop is a total game-changer. It’s like having a map to guide you through the Docker world, making it much easier to navigate, especially if you’re just starting out with containers.

But hold on, there’s more! Not only does it give you a GUI, but Docker Desktop also comes with the full Docker Engine and integrated Kubernetes support. Now, if you’re not familiar with Kubernetes, here’s the deal: it’s a powerful system for managing containerized applications. Let’s say you’re building something complex with multiple containers all working together—Kubernetes is what helps you manage all of them. Docker Desktop bundles Kubernetes into the mix, making it super handy for development and testing environments, where managing multiple containers is essential.

Let’s get down to the details. To install Docker Desktop on Ubuntu, all you need to do is download the .deb package from Docker’s official website. Once you’ve got it, just run this command:

$ sudo apt install ./docker-desktop-<version>–<arch>.deb

Easy enough, right?

Before you start the installation, it’s always a good idea to check Docker’s official documentation. Docker updates its tools regularly, and the docs will help ensure you’re following the latest steps and meeting system requirements, making the whole process smooth and hassle-free.

Docker Official Documentation

So, whether you’re just experimenting with Docker, developing complex apps, or building out your containerized setup, Docker Desktop on Ubuntu is definitely worth a try. It might just become your new best friend in the world of containers.

Installing Docker Using a Dockerfile

Imagine you’re working on a project where consistency and automation are key—maybe you’re setting up Docker on several machines, or perhaps you need to replicate an environment over and over again. Docker is already a great tool for running containers, but how do you ensure every installation is exactly the same and runs smoothly? This is where a Dockerfile comes in to make your life easier.

A Dockerfile is like a recipe. It’s a script with instructions that tell Docker exactly how to build an image. Think of it as the blueprint for setting up Docker automatically, making sure everything is in place without needing to manually configure each step. It’s not just about Docker containers; it’s about setting the environment just right every time.

Let’s dive into an example. You want to install Docker on an Ubuntu 20.04 system, and you want to do it the smart way—automatically. Here’s what the Dockerfile looks like:

FROM ubuntu:20.04
RUN apt-get update & 
    apt-get install -y apt-transport-https ca-certificates curl gnupg lsb-release & 
    curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add – & 
    add-apt-repository “deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable” & 
    apt-get update & 
    apt-get install -y docker-ce docker-ce-cli containerd.io

Let’s break it down so it makes sense. Think of each part as a chapter in a recipe book.

FROM ubuntu:20.04 – This is your base. You’re starting with Ubuntu 20.04 as the foundation. It’s like choosing a brand-new, clean kitchen for your cooking session.

RUN apt-get update – Before you start cooking, you need to make sure everything’s up to date in your kitchen. This command updates your Ubuntu system with the latest package info.

apt-get install -y – Here’s where you bring in the ingredients. You’re installing packages like apt-transport-https, ca-certificates, curl, gnupg, and lsb-release—all necessary for adding Docker’s official GPG key and repository.

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add – – This step adds Docker’s key to your system, ensuring that the Docker packages you’re downloading are the real deal. You don’t want untrustworthy ingredients in your setup, right?

add-apt-repository – This command adds Docker’s official repository to your system’s list of trusted sources. It’s like adding a trusted supplier to your list.

apt-get install -y docker-ce docker-ce-cli containerd.io – Finally, you install the main ingredients: Docker Engine, Docker CLI, and containerd. These are the key components to get Docker up and running on your machine.

Once your Dockerfile is ready, Docker will automatically fetch everything it needs and install Docker with no extra effort on your part.

But what if you want to level up and automate things even further? Here’s where Ansible comes in. Ansible is a tool that can help automate the installation of Docker across multiple machines. It’s like having a personal assistant who ensures that every machine gets the same exact setup. With Ansible , you can write playbooks that automate everything—from installing Docker to configuring Docker Compose and more.

This is especially useful when managing large infrastructures or different environments. With Ansible , you can automate these tasks, ensuring everything is set up correctly and efficiently every time. Imagine not worrying about human error when deploying Docker across many machines. That’s why Ansible is such a powerful tool.

If you’re interested in using Ansible for Docker, there are plenty of guides out there to help you. Whether it’s installing Docker, setting up Docker Compose, or managing a network of Docker instances, Ansible can make everything smoother. Plus, you’ll have a more consistent and repeatable setup across the board—what’s not to love?

By using Dockerfiles and Ansible together, you can streamline your Docker setup and make sure every deployment goes as smoothly as possible. No more hassle. Just automation and consistency. You’ve got this!

How to Uninstall Docker on Ubuntu

So, you’ve been using Docker on your Ubuntu system, but now it’s time to move on. Whether you’re troubleshooting, cleaning up, or switching to something else, you need to make sure Docker is completely removed—without leaving any mess behind. Luckily, it’s easier than you might think. Let’s go step by step to make sure everything gets wiped clean, from Docker packages to any leftover data.

First, let’s take care of the core Docker components. You know, Docker Engine, the Docker CLI, and containerd. These are the heart of Docker, and to properly remove Docker, they need to go too. You’ll use the apt package manager to purge them. It’s like tidying up your workspace—getting rid of all the clutter. Here’s the command you’ll need:

$ sudo apt purge docker-ce docker-ce-cli containerd.io

This command doesn’t just uninstall Docker; it also gets rid of all the configuration files associated with these components, so there’s no trace left behind.

But wait—Docker is a sneaky one. Even after uninstalling the packages, there might still be some leftover data hanging around. Things like Docker images, containers, volumes, and other data might still be sitting on your system. To make sure everything is completely gone, you need to manually remove the directories where this data is stored. It’s like giving your system a final clean sweep. Run these commands to clear it all out:

$ sudo rm -rf /var/lib/docker

$ sudo rm -rf /var/lib/containerd

These commands delete the directories where Docker stores all its images, containers, volumes, and persistent data. You’ll want to do this step, or you might find some Docker leftovers still hanging around, like ghost files on your system.

Next, if you added your user to the Docker group (which you probably did to avoid typing sudo every time), you might want to clean up that group too. After all, we’re aiming for a clean slate here. To remove the Docker group, just run:

$ sudo groupdel docker

Now, you might be wondering, “What about all those extra packages that Docker pulled in during the installation? Do I need to get rid of those too?” Good question! After uninstalling Docker, there could be some leftover dependencies that aren’t being used anymore. No problem—this is a quick fix. Just run:

$ sudo apt autoremove

This command will do a little spring cleaning and remove any packages that were installed as dependencies but are no longer needed by anything else on your system.

By following these steps, you’ll ensure that Docker is completely gone from your Ubuntu system—nothing left behind. You’ll walk away knowing that your system is fresh, clean, and Docker-free. You’ve got this!

Conclusion

In conclusion, mastering Docker on Ubuntu 20.04 is essential for anyone working with containerized applications. This guide has walked you through the entire process, from installing Docker and managing containers to utilizing Docker Compose for multi-container setups. With the knowledge of committing changes to Docker images and pushing them to Docker Hub, you’re well-equipped to build and deploy your containerized environments. As containerization continues to grow, Docker and Docker Compose will remain critical tools in streamlining development workflows. Stay up-to-date with future updates to ensure you’re making the most of these powerful tools on Ubuntu.

Master Docker Installation and Management on Ubuntu 20.04