My favorite material from Codio's Container Basics on Coursera
Container Creation and Orchestration Basics | Codio
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 \
$(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin
docker --version
docker compose version
Docker version 23.0.1, build a5ee5b1
Docker Compose version v2.16.0
sudo mkdir code
sudo touch code/numbers.txt
8
4
3
1
7
22
48
100
9
sudo touch code/evenOdd.sh
#!bin/bash
file='numbers.txt'
while read number; do
remainder=$((number%2))
if [ $remainder == 0 ]; then
echo "Number is even"
else
echo "Number is odd"
fi
done < $file
cd ..
sudo docker login
sudo touch code/Dockerfile
FROM centos
ADD . /code
WORKDIR /code
ENTRYPOINT ["bash", "evenOdd.sh"]
sudo docker build code/
sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
<none> <none> 7553068eca5c 6 seconds ago 231MB
hello-world latest feb5d9fea6a5 17 months ago 13.3kB
sudo docker build -t even-odd code/
sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
even-odd latest 7553068eca5c 16 minutes ago 231MB
hello-world latest feb5d9fea6a5 17 months ago 13.3kB
sudo docker run --name eo-container even-odd
This is a very simple example of a running a custom image in a container. The general process, however, is common. Create a Dockerfile specific to our needs. We chose our own operating system, copied over the files we need, and then gave a command to run an application. The resulting container is an isolated environment that runs our application on startup and then stops once the application is done.
cat server/server.py
from http.server import BaseHTTPRequestHandler, HTTPServer
class ContainerRequests(BaseHTTPRequestHandler):
def do_GET(self):
self.send_response(200)
self.send_header('Content-type', 'text/html')
self.end_headers()
self.wfile.write('Hello from a Docker container\n'.encode())
def do_POST(self):
self.send_response(200)
self.send_header('Content-type', 'text/html')
self.end_headers()
self.wfile.write('Hello from port 9000.\n'.encode())
host = '0.0.0.0'
port = 9000
HTTPServer((host, port), ContainerRequests).serve_forever()
sudo touch server/Dockerfile
FROM python
Add . /code
WORKDIR /code
ENTRYPOINT ["python", "server.py"]
sudo docker build -t python_server server/
sudo docker run -d --name web_server python_server
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8e7877cbeb26 python_server "python server.py" 17 seconds ago Up 16 seconds web_server
We can add a flag when running our image to map a port on the Linux VM to the port in the container. Before we can do that, we first need to remove the web_server container.
sudo docker stop web_server
sudo docker rm web_server
sudo docker run -p 80:9000 -d --name web_server python_server
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1056057c44f4 python_server "python server.py" About a minute ago Up About a minute 0.0.0.0:80->9000/tcp, :::80->9000/tcp web_server
curl 0.0.0.0:80
curl -X POST 0.0.0.0:80
Hello from a Docker container
Hello from port 9000.
sudo docker stop web_server
Containers need an operating system but they are also environments to run specific applications. That means they may need special packages installed as well. Instead of building on top of a general purpose image like CentOS, you can select an image for a specific programming language, database, web server, or other tools like load balancers, content management, etc.
Choosing one of these task-specific images as a starting point offers a convenience of not having to specify which software you have to install. On the last page, the base image in our Dockerfile was python. We used this instead of centos so that we did not have to install Python ourselves.
sudo touch birthday/Dockerfile
FROM alpine
ADD . /code
WORKDIR /code
RUN apk add py3-pip python3
RUN python3 -m pip install -r requirements.txt
ENTRYPOINT ["python3", "main.py"]
sudo docker build -t birthday-image birthday/
sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
birthday-image latest 92f31c7d65ec 9 seconds ago 85.9MB
python_server latest 3c61b2f2d123 10 minutes ago 921MB
even-odd latest 7553068eca5c 32 minutes ago 231MB
hello-world latest feb5d9fea6a5 17 months ago 13.3kB
sudo touch code/passwords.txt
Super-secret password
sudo docker build -t even-odd:0.2 code/
sudo docker run -d -t --name secrets even-odd:0.2
Stop all running containers with a single command.
sudo docker stop $(sudo docker container ls -q)
