2_dockerfile

Make your own image

Prerequisites

1. Clone this repository git clone https://github.com/bossan/docker-workshop
2. Go to the folder docker-workshop/examples/dockerfile.

Build an image from the Dockerfile

Run the following command to build an image:

docker build -t workshop-app .

• build: because we want to build the image
• -t workshop-app: 'tags' the image, so it has a readable name
• . means we select the Dockerfile in the current directory

Run the container

Run the following command to start the container:

docker run -d -p 3000:3000 workshop-app

• run: because we want to run a container
• -d: to run it in 'detached' mode (runs in the background)
• -p 3000:3000: means we enable port-forwarding from port 3000 on our local computer to 3000 in the container
• workshop-app: the tag of the image we created earlier

Check running containers

Run the following command:

docker ps

Open the app

Go to http://localhost:3000 to see what the app does.

Using play-with-docker? Instead of opening localhost:3000 you should click on the "OPEN PORT" button and fill in 3000. This should open a new page with the application.

Run even more containers

It is possible to run multiple containers based on the same image. You can use the following command to start another container:

docker run -d -p 3001:3000 --name second-container workshop-app

• run: because we want to run a container
• -d: to run it in 'detached' mode (runs in the background)
• -p 3001:3000: means we enable port-forwarding from port 3001 on our local computer to 3000 in the container. (Port 3000 is already in use by the other container).
• --name second-container: we can give the container a nice name instead of Docker automatically generating a name for us.
• workshop-app: the name of the image we created earlier

Stop the running containers

Before we continue to the next step, you should stop all running containers.

First check which containers are running with:

docker ps

This should look something like:

CONTAINER ID   IMAGE            COMMAND                  CREATED          STATUS          PORTS                    NAMES
9123b9d77e25   workshop-app     "docker-entrypoint.s…"   3 seconds ago    Up 2 seconds    0.0.0.0:3001->3000/tcp   second-container
c529fce32424   workshop-app     "docker-entrypoint.s…"   14 seconds ago   Up 13 seconds   0.0.0.0:3000->3000/tcp   dreamy_swirles

Now you can stop each container by specifying the ID:

docker stop c529fce32424

• stop: because we want to stop the container
• c529fce32424: because it is the ID of the container (this is different on your machine)

Or

docker stop second-container

• stop: because we want to stop the container
• second-container: because it is the name of the container we created

Starting containers again

After stopping a container it is not gone. You can restart the container. For example:

docker start second-container

• start: because we want to start the container
• second-container: because we want to start this container again.

Deleting containers

If you want to delete a container, you can do so with the following command:

docker rm second-container

• rm: because we want to delete a container
• second-container: because we want to delete this specific container.

Note: You cannot delete a running container.