Docker
Dockerfiles, Images and Containers
Dockerfile is a file containing a set of instructions to build an Image which can be used to start a Docker container.
Analogy:
Dockerfile = Makefile
Image == binary
Container == running process
Example of a Dockerfile:
FROM node
WORKDIR /app
COPY . /app
RUN npm install
EXPOSE 80
CMD ["node", "server.js"]
Running docker build . inside a directory containing this Dockerfile will build the image.
EXPOSE 80 line is just for documentation purposes. To actually expose and bind to a port
use: docker run -p 3333:80 IMAGE.
COPY . . copies from local directory into the image WORKDIR.
If RUN npm install runs during image building, CMD ["node", "server.js"] runs when the container is started.
Commands
docker build . Build an image from a Dockerfile located in working directory
docker run IMAGE Run a built image
docker ps Show running containers
docker ps -a Show all containers (default shows just running)
docker run -p 3000:80 IMAGE Run a container and bind to local 3000 exposed container 80
Getting inside a container
docker attach will let you connect to your Docker container, but this isn't really the same thing as ssh. If your
container is running a webserver, for example, docker attach will probably connect you to the stdout of the web server
process. It won't necessarily give you a shell.
docker exec -it <CONTAINER ID> bash
This is useful when you have for example a MySQL server running inside a container. Once you're inside with docker exec you can
just connect to your db with mysql -h 127.0.0.1 -P 3306 -u root -p or whatever ports/user/pass you are using.