Docker File

A Docker file is a text document that contains all the commands a user could call on the command line to assemble an image.

docker build -f <path_of_docker_file>

From

FROM <image>[:<tag>]

Run (execute commands on top of current image)

Example:

RUN apt-get update

RUN apt-get install -y curl

Cmd (Run the software contained in the image, basically executing the image in the container)

There can be only one cmd instruction in the docker file

CMD ["executable","param1","param2"]

Expose (Indicates the port on which the container is listening for connections)

Expose <port>

Env (To set environment variable for the application)

Add

Volume

Workdir

Building a custom docker image using docker file

Docker file

# Each instruction in this file generates a new layer that gets pushed to your local image cache

# The line below states we will base our new image on the Latest Official Ubuntu

FROM ubuntu:latest

# Identify the maintainer of an image

LABEL version="0.0.1"

LABEL maitainer="anshulc55@gmail.com"

# Update the image to the latest packages

RUN apt-get update && apt-get upgrade -y

# Install NGINX to test.

RUN apt-get install nginx -y

# Expose port 80

EXPOSE 80

# Last is the actual command to start up NGINX within our Container

CMD [ "nginx", "-g", "daemon off;"]

To execute this docker file to create a custom image

docker image build -t customnginx:0.0.1(Image name with tag) .(directory of dockerfile)

To run the built custom docker image in a container

docker run -d -p 8080:80 customnginx

# This will make nginx accessible to outside world on port 8080. We have used port 80 because in docker file we have exposed port 80 for listening.

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