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April 2017

Recap part of March with starting from Page 80

  • docker login: login to docker to get / push to your private images

get basic container

docker run -i -t ubuntu /bin/bash (inside container) apt-get update apt-get install apache2 exit

docker commit <CONTAINER_ID> btmash/apache2 -m "My new ubuntu image with apache" -a "Ashok Modi"

  • 'docker images' will now list custom image with namespace
  • 'docker inspect btmash/apache2' will now list comment and author

dockerfile

  • Instead of manually typing commands inside running container, build using dockerfile '''

You must specify a base image

FROM ubuntu:16.04

This is meta information. Not necessary but still good to have

MAINTAINER Ashok Modi 'btmash@gmail.com'

Use an environment variable if you want to easily get packages updated

ENV REFRESHED_AT 2017-04-20

The real meat and bones

RUN apt-get update; apt-get install -y nginx RUN echo 'My first web page' > /var/www/html/index.html EXPOSE 80 '''

Each line in above is a new layer and will get cached. If you add anything in middle, the lines below are no longer cached and will re-run. Any new lines introduced to end of file will be run and then cached. In above case, I can get image rebuilt by just updating REFRESHED_AT env without touching rest of file.

Use

  • docker build
    • Builds docker container based on docker file
  • docker build -t="btmash/static_nginx"
    • Builds docker container and will give it name 'btmash/nginx'
  • docker build -t="btmash/static_nginx:v1"
    • Builds docker container and will give it name 'btmash/nginx' and tag 'v1' (defaults to latest otherwise)

docker run -d -p 80 --name static_web btmash/nginx nginx -g "daemon off;"

  • -d: Run as a daemon
  • -p: Expose a port.
    • Format would be PORT_ON_MACHINE:PORT_ON_CONTAINER
    • If you specify port without :, port 80 from container above would be exposed and assigned a random port from machine for user to access (so you might access site at http://127.0.0.1:49024)
    • If you specify at 80:80, port 80 from container would be exposed and assigned port 80 from machine for user to access (so you might access site at http://127.0.0.1).
    • If you specify at 8080:80, port 80 from container would be exposed and site would be accessed at http://127.0.0.1:8080
    • Use this to also assign to specific interface (like 127.0.0.1:80:80)
      • Or to a random port (like 127.0.0.1::80)
  • -P: Expose all ports identified in dockerfile

More dockerfile commands

Some are CMD, ENTRYPOINT, ADD, COPY, VOLUME, WORKDIR, USER, ONBUILD, LABEL, STOPSIGNAL, ARG, SHELL, HEALTHCHECK and ENV

  • CMD
    • Runs AFTER container has built.
    • Specify in array format to be very clear. ex CMD ['/bin/bash', '-l'] will be interpreted as /bin/bash -l
  • ENTRYPOINT
    • Similar to CMD
    • CMD would be default instruction after container is built. ENTRYPOINT overrides start instruction