Dockerfile - some basic best practices

Create a new docker file - Dockerfile

FROM alpine:3.4MAINTAINER Deiveehan Nallazhagappan deiveehan@gmail.com

RUN apk update
RUN apk add vim

Go to the prompt and say docker build -t deiveehan/alpine-extend .

This should create the image.

What is image cache: 

This is the image cache that gets built for each every docker command in the docker file. 

This is done because if you add more to the docker file, it wont take time by creating from scratch. 

For example if I add one more line to add git. 

FROM alpine:3.4MAINTAINER Deiveehan Nallazhagappan deiveehan@gmail.com

RUN apk update
RUN apk add vim
RUN apk add git

then it assembles till "add vim" from the local image cache and then builds only the add git. 

Best practices:
1. manage the RUN commands or any lines in the docker file that dont change frequently in the top and one that changes in the bottom. 

You can do like this
RUN apk update && \
    apk add curl && \
    apk add vim && \
    apk add git

so that it does not create multiple local image caches. 

2. Pick the right image (a slim image)

3. DO it yourselves: Go to the shell and start typing commands that helps build the image and the steps in the before step and include them in the docker file
This is better than blindly following some web sites.