Docker Workshop

This is a practical workshop on using Docker for developing and deploying applications.

git clone https://github.com/rosedu/workshop-docker
cd workshop-docker/

And let's get going! 🚀

Note

If, at any point in time, you miss a command, or something bad simply happened, reset the environment by running:

./reset-all.sh

Important

We re recommend you write all commands below by hand, i.e. without using copy & paste. This will get you better accustomed to the Docker ecosystem.

Initial Setup

Follow the steps below for an initial setup of the environment.

Create a DockerHub Account

Sign up for a DockerHub account. We will use it for exercises below.

Install Docker

Warning

You will probably be unable to run Docker properly in macOS environment. If you have a macOS environment, use a virtual machine, such as the Intro to Operating Systems Virtual Machine.

Install Docker on a Debian-based system (such as Ubuntu, including on Windows Subsystem for Linux (WSL), by running the script:

./install-docker.sh

It will take a while to run.

If the script above fails for any reason, install Docker by following these instructions.

Important

Make sure to add your user to the docker group so you can run the docker commands without sudo. Follow the post-installation steps to have Docker running as non-root user.

To validate your Docker installation, run the command:

docker version

If the command above runs OK, Docker will run successfully.

Set Up Initial Environment

Set up an initial Docker environment by running the script:

./reset-all.sh

The script will (re)create two containers (cdl-nginx and ctf-piece_of_pie) that we will use in the exercises below.

Inspect Docker Instances

Let's start with inspecting the Docker installation and instances on the virtual machine.

Follow the steps below:

See available docker commands:
```
docker help
```
Check the docker version:
```
docker version
```
See information about the docker installation:
```
docker info
```

Find out the currently running Docker containers:

docker ps

You will the Docker containers that are currently running, namely an Nginx container:

CONTAINER ID   IMAGE          COMMAND                  CREATED       STATUS          PORTS                                     NAMES
fbfe1d0b5870   nginx:latest   "/docker-entrypoint.…"   6 hours ago   Up 38 seconds   0.0.0.0:8080->80/tcp, [::]:8080->80/tcp   cdl-nginx

Find out all containers, including those that are stopped:

docker ps -a

A new container, named ctf-piece_of_pie is now visible:

CONTAINER ID   IMAGE              COMMAND                  CREATED          STATUS                        PORTS                                     NAMES
16a526c7c94c   ctf-piece_of_pie   "/usr/local/bin/run.…"   24 minutes ago   Exited (137) 51 seconds ago                                             ctf-piece_of_pie
fbfe1d0b5870   nginx:latest       "/docker-entrypoint.…"   6 hours ago      Up 40 seconds                 0.0.0.0:8080->80/tcp, [::]:8080->80/tcp   cdl-nginx

Find out port-related information about the cdl-nginx container that is running:
```
docker port cdl-nginx
```
You can see the port forwarding:
```
80/tcp -> 0.0.0.0:8080
80/tcp -> [::]:8080
```
You can check the current install by querying the server:
```
curl localhost:8080
```
You will see the default HTML page of Nginx.

No information is shown for containers that are not running:
```
docker port ctf-piece_of_pie
```
Get detailed information about the Docker instances, either started or stopped:
```
docker inspect cdl-nginx
docker inspect ctf-piece_of_pie
```
Find out of the runtime logging information of the container:
```
docker logs cdl-nginx
docker logs ctf-piece_of_pie
```
Find out runtime statistics and resource consumption of the running Nginx container:
```
docker stats cdl-nginx
```
Close the screen by running Ctrl+c three times.
Find out the internal processes of the running Nginx container:
```
docker top cdl-nginx
```

Do It Yourself

Repeat the steps above, at least 2-3 times.

Now, let's use the steps above on different containers. Start two new containers named cdl-caddy and cdl-debian-bash by running the corresponding scripts:

./vanilla-caddy/run-caddy-container.sh
./debian-bash/run-debian-bash-container.sh

Inspect the two newly started containers using the commands above.

Interact with Docker Instances

Let's now do actual interaction with Docker container instances. Such as starting and stopping containers, copying files to / from containers, getting a shell inside containers etc.

Follow the steps below.

Start Instances

Start the ctf-piece_of_pie instance:

docker start ctf-piece_of_pie

Now check it is started:

docker ps

You can see it appears as a started container.

Check the ports and the processes:

docker port ctf-piece_of_pie
docker top ctf-piece_of_pie

Connect locally to test the service:

nc localhost 31337

Stop Instances

Stop the cdl-nginx instance:

docker stop cdl-nginx

You can see it does not appear as a started container.

Check to see the list of stopped containers:

docker ps -a

Remove Containers

A stopped container can be removed. Once this is done, the container is gone forever. It will have to be re-instantiated if needed, as we'll see in section "Images and Containers".

Remove the cdl-nginx container:

docker rm cdl-nginx

The container is now gone. You can use different commands to see if is gone:

docker ps -a
docker inspect cdl-nginx
docker stats cdl-nginx

Connect to a Container

You can connect to a container by using docker exec. Typically, you want to start a shell. Start a shell on the ctf-piece_of_pie container by using

docker exec -it ctf-piece_of_pie /bin/bash

More than that, you can run different commands inside the container:

docker exec -it ctf-piece_of_pie ls
docker exec -it ctf-piece_of_pie ls /proc
docker exec -it ctf-piece_of_pie cat /etc/shadow
docker exec -it ctf-piece_of_pie id

Copy Files To / From a Container

You can copy files or entire directories to or from a container. For example, to copy the README.md file to the cdl-nginx container in the root/ directory, use:

docker cp README.md cdl-nginx:/root/

Likewise, if we want to copy the index.html file we use:

docker cp cdl-nginx:/usr/share/nginx/html/index.html .

Note: There is a period (.) at the end of the command above. It is required, it points to the current directory.

You can see that the container doesn't need to be running.

Do It Yourself

Make sure all four containers are started: cdl-nginx, ctf-piece_of_pie, cdl-caddy, cdl-debian-bash. Start them if they are not stared.

Copy files to and from containers.

Copy README.md and install-docker.sh files from the current directory in the /usr/local/ directory in all containers available (via docker ps -a).
Copy the ctf/ local directory in the /usr/local/ directory in all containers available (via docker ps -a).
Create a directory for each available container:
```
mkdir container-cdl-nginx
mkdir container-ctf-piece_of_pie
mkdir container-cdl-caddy
mkdir container-cdl-debian-bash
```
Copy the /bin/bash binary from each available container to their respective directory.

Copy the /etc/os-release file from each available container to their respective directory. Check the contents to see what Linux distro was used to construct the filesystem.

Docker Images

Images are stored locally either by being pulled from a container registry such as DockerHub (see section "Getting Images") or from a Dockefile (see section "Dockerfile").

List the available Docker images by using:

docker image ls

You will get an output such as:

REPOSITORY         TAG        IMAGE ID       CREATED        SIZE
ctf-piece_of_pie   latest     1f844c4f935b   9 hours ago    209MB
<none>             <none>     99ba2c76892a   9 hours ago    216MB
<none>             <none>     e81d4254c928   13 hours ago   209MB
<none>             <none>     2d74afaf7b34   13 hours ago   209MB
debian             bookworm   617f2e89852e   2 weeks ago    117MB
nginx              latest     3b25b682ea82   4 weeks ago    192MB
gcc                14.2       d0b5d902201b   3 months ago   1.42GB

The <none> entries store intermediary versions of an image file.

You can also inspect an image, such as debian:bookworm.

docker image inspect debian:bookworm

Images and Containers

As stated above, containers are created from images. Let's re-create the Nginx container, starting from the nginx:latest image:

docker create --rm --name cdl-nginx nginx:latest

Check out it was created by running:

docker ps -a

The container is currently stopped. In order to start the container, run:

docker start cdl-nginx

Check out it was started by running:

docker ps
docker logs cdl-nginx
docker inspect cdl-nginx
docker stats cdl-nginx

The create and start command can be combined in a single command, docker run.

Create two more Nginx containers by running docker run:

docker run --rm --name cdl2-nginx -p 8882:80 nginx:latest
docker run --rm --name cdl3-nginx -p 8883:80 nginx:latest

Check whether they are running:

docker ps
docker stats cdl2-nginx
docker stats cdl3-nginx
curl localhost:8882
curl localhost:8883

The --rm option will remove an Nginx instance once it is stopped.

Stop the instances:

docker stop cdl2-nginx
docker stop cdl3-nginx

Now the containers are gone forever (because of the --rm option):

docker ps -a

Do It Yourself

Create more Nginx instances from available images:

Use docker run to create 5 more Nginx images from the nginx:latest image. Make sure you use different public ports.

Use the --rm option of docker run.
Stop the containers you have just started.
Check they are gone forever.

Getting Images

Images are stored locally either by being pulled from a container registry such as DockerHub (see section "Getting Images") or from a Dockerfile (see section "Dockerfile).

To search for an image you like, use the commands below:

docker search database

To pull images locally, use:

docker pull <container-image-name-and-path-in-regitry>

such as:

docker pull nginx:latest
docker pull gcc:14.2

Do It Yourself

Download and instantiate other images.

Download images the applications: MongoDB, MariaDB. Use the names mongodb/mongodb-community-server:latest and mariadb:latest.
Create 5 container instances for MongoDB and 5 container instances for MariaDB. Use the --rm option for docker run.
Check to see the container instances are running.
After a while, stop the newly instances.

Dockerfile

Dockerfiles provide recipes for creating images. The images can then be instantiated into containers.

Check Dockerfiles

Check the Dockerfile used by the ctf-piece-of-pie container.

Also check the following Dockerfiles:

linux-kernel-labs defines a Docker container.
uso-lab
dropbox

This is a brief overview of the main keywords in a Dockerfile:

FROM - the base container on top of which the setup will be done;
RUN - runs a setup command;
WORKDIR - sets the container work directory to the specific path;
USER - sets the running user to the specific username;
ARG - defines an argument at build time;
COPY - copies a file from the build directory to the container.

The Dockerfile reference presents an extensive presentation of keywords in a Dockerfile.

Build Images from Dockerfiles

All four Dockerfiles presented above are part of the dockerfile/ directory. Let's use them to create Docker images:

Build the CTF Docker image:
```
docker build -f dockerfile/ctf.Dockerfile -t my-ctf ctf/
```
The options in the above command are:
- -f dockerfile/ctf.Dockerfile: the path to the Dockerfile used to build the image
- -t my-ctf: the image name (also called a tag)
- ctf/: the directory that will be used as the base for COPY commands
Running the command above results in the creation of the my-ctf image.

Build the linux-kernel-labs Docker image:

docker build -f dockerfile/linux-kernel-labs.Dockerfile -t linux-kernel-labs .

Running the command above results in an error:

=> ERROR [32/36] RUN groupadd -g $ARG_GID ubuntu
------
 > [32/36] RUN groupadd -g $ARG_GID ubuntu:
0.207 groupadd: invalid group ID 'ubuntu'
------
linux-kernel-labs.Dockerfile:42
--------------------
  40 |     ARG ARG_GID
  41 |
  42 | >>> RUN groupadd -g $ARG_GID ubuntu

This is caused by missing build arguments ARG_UID and ARG_GID. We provide these arguments via the --build-arg option:

docker build -f dockerfile/linux-kernel-labs.Dockerfile --build-arg ARG_GID=$(id -g) --build-arg ARG_UID=$(id -u) -t linux-kernel-labs .

Running the command above results in the creation of the linux-kernel-labs image.

Build the uso-lab Docker image:

docker build -f dockerfile/uso-lab.Dockerfile -t uso-lab .

Running the command above results in an error:

 => ERROR [15/16] COPY ./run.sh /usr/local/bin/run.sh
------
 > [15/16] COPY ./run.sh /usr/local/bin/run.sh:
------
uso-lab.Dockerfile:20
--------------------
  18 |     RUN rm -rf /var/lib/apt/lists/*
  19 |
  20 | >>> COPY ./run.sh /usr/local/bin/run.sh
  21 |     CMD ["run.sh"]

This is because the run.sh script is not available in the local filesystem. You will fix that as a task below.

Build the dropbox Docker image:

docker build -f dockerfile/dropbox.Dockerfile -t dropbox .

Running the command above results in a similar error as above:

=> ERROR [9/9] COPY ./run.sh /usr/local/bin/run.sh
------
 > [9/9] COPY ./run.sh /usr/local/bin/run.sh:
------
dropbox.Dockerfile:80
--------------------
  78 |
  79 |     # Install init script and dropbox command line wrapper
  80 | >>> COPY ./run.sh /usr/local/bin/run.sh
  81 |     CMD ["run.sh"]

This is because the run.sh script is not available in the local filesystem. You will fix that as a task below.

Do It Yourself

Fix Build Issue

First, fix the issue with the creation of the uso-lab image. That is:

Copy the run.sh script locally.
Run the docker build command again. Be sure to pass the correct path as the final argument to the docker build command. This is the path where the run.sh script is located locally.

Follow similar steps to fix the issue with the creation of the dropbox image.

Images from Other Dockerfiles

Search the Internet (GitHub or otherwise) for two Dockerfiles. Build images from those two Dockerfiles.

Python Server

Go to the python-server/ directory and build the container using the following command:

docker build -t python-server:1.0 .

The command builds the container with the specification from the Dockerfile. Run the container:

docker run -p 8888:8888 --name python-server python-server:1.0

Test the container functionality by running:

curl localhost:8888

Change the base image to Debian and rebuild the container tagged with the python-server-debian:1.0 tag.

Create a Makefile with has the following rules:

build: creates a new image using the Dockerfile;
start: starts a container based on the python-server image named python-workspace in the background;
stop: stops the python-workspace container;
connect: connects to the container in an interactive shell.

Assignment Checker

A common use case for using containers is platform-agnostic testing. The assignment-checker/ directory contains a bash scripts which runs tests on an application by running it and comparing its output with a reference.

Create a Docker image which is able to run this script, compile de application and run the tests.

Volumes

While it makes sense to run Docker containers by themselves as services, all the data that they produce is ephemeral and will be deleted when the container is destroyed.

To provide an input to the containers and a permanent storage for them we use Docker volumes.

Volumes are used to save outputs of files permanently.

Set Up Test Container

Enter the perpetual-writer/ directory and build and run a container that periodically (once every 5 seconds) writes a message to a log file:

cd perpetual-writer/
make run

The command above starts the perpetual-writer container:

$ docker ps
CONTAINER ID   IMAGE              COMMAND                  CREATED             STATUS             PORTS                                     NAMES
81353bb256cb   perpetual-writer   "bash /run.sh"           4 seconds ago       Up 2 seconds                                                 perpetual-writer

To check the generation of messages, enter the container:

docker exec -it perpetual-writer /bin/bash

And now check the output of the log file in the /perpetual-logs/logs file:

root@34c8d901cc21:/# cat /perpetual-storage/logs
I have been running as of Sat Mar 29 08:00:16 UTC 2025
I have been running as of Sat Mar 29 08:00:21 UTC 2025
I have been running as of Sat Mar 29 08:00:26 UTC 2025
[...]

Exit the container:

root@34c8d901cc21:/# exit

And stop and remove the container:

make clean

Run the Container with Bind Mount

In the example above, we were able to run the container and see the generated content while inside the container. But for a majority of use cases, we would want to be able to retrieve the output from (and feed the input to) the container.

For this, we do a bind mount of a local directory to the container. This will mount the local directory in the container; any updates to the directory will be synced between the local setup and the container.

To see the bind mount in action, first create the local directory perpetual-storage/:

mkdir perpetual-storage

And then start a container using the perpetual-writer image and bind mount the local directory perpetual-storage to the container. The bind mount point in the container is /perpetual-storage:

docker run -d --name perpetual-writer -v $(pwd)/perpetual-storage:/perpetual-storage -t perpetual-writer

The container is now running. It generates output in the /perpetual-storage/logs file inside the container. And, because of the bind mount, that file is available, and its contents are synced on the local perpetual-storage/ directory:

$ ls perpetual-storage/
logs

$ cat perpetual-storage/logs
I have been running as of Sat Mar 29 09:20:51 UTC 2025
I have been running as of Sat Mar 29 09:20:56 UTC 2025

$ cat perpetual-storage/logs
I have been running as of Sat Mar 29 09:20:51 UTC 2025
I have been running as of Sat Mar 29 09:20:56 UTC 2025
I have been running as of Sat Mar 29 09:21:01 UTC 2025

In the above commands, we can see the file perpetual-storage/logs being updated as the container runs.

Stop it and remove the container:

docker stop perpetual-writer
docker rm perpetual-writer

The perpetual-storage/logs file is now no longer updated.

Now, start a new container based on the same image using the same command. Enter the container and check the content of the /perpetual-storage/logs file. The file is now again updated. So we have a persistent storage that we can share to different container runs.

More Bind Mounts

Let's run the nginx container using content on our host system, from the nginx-website/ directory.

docker run -d --name simple-nginx -v $(pwd)/nginx-website:/usr/share/nginx/html:ro -p 8085:80 nginx

Check the website with curl:

$ curl localhost:8085
Simple NGINX server

It works. We served local content (in the nginx-website/ directory) by using a bind mount to /usr/share/nginx/html/, and serving the content with Nginx inside the container. The nginx-website/ directory is mounted to the /usr/share/nginx/html/ directory, the root directory of Nginx.

Run another container to serve content from the better-website/ local directory:

docker run -d --name better-nginx -v $(pwd)/better-website:/usr/share/nginx/html:ro -p 8086:80 nginx

Check the website with curl:

$ curl localhost:8086
<!DOCTYPE html>
<html>
    <head>
        Better website
    </head>
    <body>
        <strong>I'm simply better</strong>
    </body>
</html>

It works.

Additional Bind Mount

Add an additional mount point to the above command to mount the nginx-confs/nginx.conf file as the Nginx configuration file fount at /etc/nginx/nginx.conf. Use a new -v ... command option.

Do It Yourself

Create a new directory yet-another-website/ and start a container and bind the directory to the container to be served with Nginx. Verify with curl.

Build Program With GCC13

An advantage of using containers is the fact that they offer a flexible environment for testing and building applications. Based on this Dockerfile, create a Docker image which compiles an application based based on a Makefile located in the /workdir path.

The container must be able to compile applications using GCC13.

The application to be compiled is located in assignment-checker/src. Use the included Makefile to compile it.

Container Registries

Now that we have created a set of containers, we want to publish them so they are available to the world and to download on other systems.

To push the python-container image that we have built earlier, we will need to tag it so that it has an associated namespace as such:

docker tag python-container:1.0 <dockerhub-username>/python-container:1.0

Where <dockerhub-username> is your DockerHub username.

To push the container you will use the docker push command:

docker push <dockerhub-username>/python-container:1.0

Tag the assignment-checker container and push it to DockerHub.

Using GitHub Container Registry

While using DockerHub offers great visibility for projects and container images, it limits the number of pulls for images on a specific IP. To bypass this issue we will create a GitHub Container Registry (GHCR) account and login to it.

Follow the GHCR tutorial to create a GHCR account.

Login to the account the same as you did with the DockerHub account and tag the assignment-checker image to be pushed to GHCR.

Name		Name	Last commit message	Last commit date
Latest commit History 22 Commits
assignment-checker		assignment-checker
better-website		better-website
ctf		ctf
debian-bash		debian-bash
dockerfile		dockerfile
nginx-confs		nginx-confs
nginx-website		nginx-website
perpetual-writer		perpetual-writer
python-container		python-container
vanilla-caddy		vanilla-caddy
vanilla-nginx		vanilla-nginx
LICENSE		LICENSE
README.md		README.md
install-docker.sh		install-docker.sh
reset-all.sh		reset-all.sh

License

rosedu/workshop-docker

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Docker Workshop

Initial Setup

Create a DockerHub Account

Install Docker

Set Up Initial Environment

Inspect Docker Instances

Do It Yourself

Interact with Docker Instances

Start Instances

Stop Instances

Remove Containers

Connect to a Container

Copy Files To / From a Container

Do It Yourself

Docker Images

Images and Containers

Do It Yourself

Getting Images

Do It Yourself

Dockerfile

Check Dockerfiles

Build Images from Dockerfiles

Do It Yourself

Fix Build Issue

Images from Other Dockerfiles

Python Server

Assignment Checker

Volumes

Set Up Test Container

Run the Container with Bind Mount

More Bind Mounts

Additional Bind Mount

Do It Yourself

Build Program With GCC13

Container Registries

Using GitHub Container Registry

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