You can start up a temporary development environment by going to Play with Docker, you'll need to setup an account.
Your session will last 4 hours before it's reset, you can drag files onto the session or if you have an external repository such as gitlab.com or github.com you can run a git clone to pull any projects in.
A Docker container must have something to do, if the last instruction you give a docker container is to upgrade a package it would run the upgrade and then shut down.
I'll use this image as an example nginx:alpine. If you look at it's Docker file the last command is to start up nginx CMD ["nginx", "-g", "daemon off;"].
In the play with docker console run docker run -p 8080:80 nginx:alpine.
Near the top you should see the port number 8080 appear, if you click on it you'll get to the nginx test page.
docker run- Tells Docker to run a command.-p 8080:80- Maps the docker containers port 80 to the hosts port 8080.nginz:alpine- The container to use.
Start the above docker container but daemonize it with a -d so docker run -p 8080:80 -v $(pwd):/usr/share/nginx/index -d nginx:alpine.
Run docker ps under NAMES you should see the name of the container.
Run docker exec -it <container name> /bin/sh you should now find yourself in the shell of the running container.
Make a change to the web page displayed on port 8080 using vi vi /usr/share/nginx/html/index.html and change something, for example:
change
<h1>Welcome to nginx!</h1>
to
<h1>Hello, Welcome to nginx!</h1>
Create a new index.html file for nginx;
<!DOCTYPE html>
<html>
<body>
<h1>Welcome to my nginx page!</h1>
</body>
</html>
Save it to the play with Docker console and run docker run -p 8080:80 -v $(pwd)/index.html:/usr/share/nginx/html/index.html -d nginx:alpine
The web page that is displayed should now show your message.
A docker file can be used to create a new docker container.
make a new file called dockerfile and add the following:
FROM nginx:apline
COPY ./index.html /usr/share/nginx/html/index.html
CMD ["nginx", "-g", "daemon off;"]
Create the index.html file that docker is going to add to the new image:
<!DOCTYPE html>
<html>
<body>
<h1>Welcome to my nginx page!</h1>
</body>
</html>
Now build the new image docker build -t "test:dockerfile" and run it docker run -p 8080:80 -d test:dockerfile.
Rather than dealing with increasingly long command lines to more complex Docker containers everything can be put into a docker compose file e.g.
version: '3'
services:
nginx:
image: nginx:alpine
ports:
- 8001:80
This is publicly available project that can creates some containers on a docker host to monitor other docker containers, possibly useful in helping debug more complex testing developement environments github.com/stefanprodan.