Docker Image
How to start
Create a File called Dockerfile without any extension with following example structure:
# Use an existing docker image as a base
From alpine
# Download and install a dependency
RUN apk add --update redis
#Tell the image what to do when it starts as a container
CMD ["redis-server"]
Then build the image via the command line through running within the directory of the Dockerfile follwing command:
docker build .
After that run the container while calling docker run <containerID>
## Convention for Tagging
For giving a tag to a docker file there is a strict convention which should be used. The convention looks like
docker build -t <YourDockerID>/<repo/Project name>:<version>
The version is always called latest for the latest image
Example :
docker build -t kn0rr/redis-server:latest .
Then you can run the image by docker run kn0rr/redis-server , by default the “latest” image is used
## Create an own image out of an running container
If you want to create an image out of an running container with some additional commands you can do it like following.
# run the container and start an interactive shell
docker run -it alpine sh
# do some stuff here which should be done in your new image e.g. install redis
apk add --update redis
Then open a new terminal to do a docker ps .
After that run addtional commands you want to execute within the container while refering to the containerID at the end e.g.
docker commit -c 'CMD ["redis-server"]' 776abe4ec8c5
NOTE: Within a Windows Terminal the command is a little bit different:
docker commit -c "CMD 'redis-server'" 776abe4ec8c5
Then you will get the new Image ID
Enhanced Build commands
To create in image where you want to integrate some data you need to ehance the Dockerfile with some further commands
# Use an existing docker image as a base
From node:alpine
# Working Directory.Specify to make sure not to copy data into root directory
WORKDIR /usr/app
# Copy the files from the build context into the current working directory
# of the container. Necessary so that package.json and index. json are
# available
COPY ./package.json ./
# Download and install a dependency
RUN npm install
# Here you can specify the files you want to copy later, because they
# change frequently, so that you make the most out of the caching
COPY ./ ./
#Tell the image what to do when it starts as a container
CMD ["npm","start"]