Docker Handbook

Docker is a way for the DevOps engineers to transfer a part of their pain to the devs.

In this handbook, you might see me using both docker and nvidia-docker, the latter is used for container which require a GPU to run. In most of the cases, these are interchangable, except for when you’re running containers which require gpus, where nvidia-docker is mandatory.

There are 5 steps to moving from your ragtag scripts to docker:

Stop running your ragtag scripts
Write a Dockerfile
Run docker build to build an image
(Optional) Push your container into a registry
Running your image locally with docker run

Writing a `Dockerfile`

Let’s first look at a very simple dockerfile:

# set base image (host OS)
FROM python:3.8

# copy the content of the local src directory to the working directory
WORKDIR /usr/local/
COPY . .

# install dependencies
RUN apt-get update
RUN pip install -r requirements.txt

# command to run on container start
ENTRYPOINT ["python","hello.py"]

The DockerFile is a way to tell docker that: ‘hey Docker, these are the things that you need to be able to build a docker image of whatever I’m working on.'. Think of it like a recipe, where the final dish to be prepared is the docker image.

COPY . . tells docker to copy everything in the current directory into the docker image which is being built. In ordr to avoid copying everything, you can use a .dockerignore file like the one shown below:

# Ignore any files or directories within the subdirectory named "modules" 
some_folder/*

# Ignore any files or directories in the context root beginning with "modules"
some_name*

I personally like to move all of the dependency installations into a different shell script called setup.sh and just run it in the dockerfile as follows:

RUN sh setup.sh

where setup.sh could be something like:

pip install --upgrade pip
pip install git+https://github.com/username/repo.git
echo 'setup complete :)'

Building an image

Once you’re ready with your dockerfile, it’s now time to build the image. This generally takes quite some time if you have tons of dependencies.

nvidia-docker build . --file Dockerfile --tag spongebob

--file: specifies the name of the dockerfile, defaults to Dockerfile
--tag think of it like the name of the image you’re building. In this case I named it spongebob

note:: nvidia-docker and docker are the same thing, except for the fact that nvidia-docker required when you want to access Nvidia GPUs later on when running the image.

Once your image has been built, you can check it out with:

docker image ls

Pushing an image into a registry

In order to push your image, you would first have to tag it

docker tag spongebob mayukhdeb/spongebob:latest

then you can push it into dockerhub as follows:

docker push mayukhdeb/spongebob:latest

Running an image locally

docker run mayukhdeb/spongebob:latest

In order to open up ports, you’ll have to use the -p and the --network args as follows:

docker run -p 5656:5656 --network="host" spongebob

And to use nvidia GPUs, you have to use the --gpus arg:

nvidia-docker run  --gpus all -p 5656:5656 --network="host" spongebob

As an extra, if you want to also pass CLI args into your script, you can simply append them into the end of the command. Let us try to pass a --friend argument into the script:

nvidia-docker run  --gpus all -p 5656:5656 --network="host" spongebob --friend="patrick"

Writing a Dockerfile#

Building an image#

Pushing an image into a registry#

Running an image locally#

Writing a `Dockerfile`

Building an image

Pushing an image into a registry

Running an image locally