dockerfile.md

Dockerfile File

Command	Purpose	Example	Notes
FROM <image>	a base image the built image is based on	FROM node:8	should be the very first command in Dockerfile and used once (in most cases)
MAINTAINER <someone>	an author of the image	MAINTAINER John Smith <john.smith@example.com>
COPY <src> [...] <dest>	copies file(s) into Docker image’s file system	COPY index.html /css www/
ADD <src> ... <dest>	works like COPY, but handles remote resources (accessible via URL) and .tar files	ADD app-icons.tar /img	files contained within TAR are extracted into destination path
ENV <name> <value>	defines an environment variable in the image	ENV hostname db_store
WORKDIR <path>	changes image’s current working directory to the given path	WORKDIR /var/www	if specified directory does not exist, it will be created
EXPOSE <port[/<protocol>]> ...	opens given port(s) (optionally along with a protocol whose default value is tcp)	EXPOSE 7000/udp	allows to connect with a service contained in the image
RUN <command>	executes given command(s)	RUN cd sass && gulp build:css	we can use any command accessible in OS like mv, tar or apt-get
CMD <command>	like RUN (differences are below)	CMD echo 'Docker service is up...'

RUN vs. CMD

• RUN - executed once when building the image
• CMD - executed every time the service is being run

Example Dockerfile

# use Node.js v.8
FROM node:8
 
# create app directory
WORKDIR /usr/src/app
 
# copy files
COPY package*.json ./
COPY ./ ./
 
# install Node dependencies
RUN npm install
 
# run the service accessible via port 8080
EXPOSE 8080
CMD "npm start"