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Docker Begins

Installations

docker

docker-compose

docker-machine

  1. find your daemon
  2. docker info

docker desktop for mac

Find symlinks find $(which docker) -type l -ls

Mac native application, that you install in /Applications find /var/run/docker.sock -type l -ls

hyperkit does not use docker-machine to create VM. docker-machine and docker desktop for mac can co-exist.

gives only one VM to run a docker daemon

docker toolbox on mac

docker-machine create -d "virtualbox" project1
docker-machine env project1
docker-machine create -d "virtualbox" project2
docker-machine env project2
eval $(docker-machine env project1)

notice docker_host URL. IP address for each VM is different

switch between docker desktop and docker toolbox
unset ${!DOCKER_*} #stop using docker-machine if any
eval $(docker-machine env project1) #set env variables to use a docker-machine

[SKIP]

Run docker command on mac but connect to docker daemon running in docker-machine

docker -H tcp://192.168.99.102:2376 --tlsverify --tlscert /Users/shadjachaudhari13/.docker/machine/machines/project1/cert.pem --tlscacert /Users/shadjachaudhari13/.docker/machine/machines/project1/ca.pem --tlskey /Users/shadjachaudhari13/.docker/machine/machines/project1/key.pem --tls ps [SKIP]

To SSH into docker-machine
eval $(docker-machine env project1)
docker run -d -p 8000:80 nginx  # browse <daemon ip>:8000 on mac's browser
docker-machine ssh project1
ping <docker-ip> # works
docker run -d nginx
ps aux | grep nginx
ping <docker-ip> # works without exposing ports

Run a container:busybox and start first process - PID 1

syntax docker run <image>

docker run busybox echo hello
docker run busybox cat /etc/hostname

container exits as PID 1 has done its job and terminated

docker run busybox sleep 300
containerid=$(docker ps | awk 'NR > 1 {print $1}')
docker top $containerid

PID 1 would be 'sleep 300'

Exit foreground container in different ways

exit ctrl+c

Run a container:busybox in interactive mode

Interactive containers are useful when you are putting together your own image. You can run a container and verify all the steps you need to deploy your app, and capture them in a Dockerfile

docker run --interactive --tty ubuntu
apt-get update && apt-get install telnet git -y
ctrl+c

stops container by exiting --tty

[TIP]

Daemonize foreground container

docker run -it ubuntu
ctrl+p Ctrl+q

tty exits but container still runs in background

Run container in background - detached mode

docker run -d ubuntu

Enter container running in detached mode

containerid=$(docker ps | awk 'NR > 1 {print $1}')
docker exec --interactive --tty $containerid bash
apt-get update

Exit background container in different ways

ctrl+c type 'exit'

stop container

  1. docker stop
  2. docker -it exec bash # stopping PID1 is stopping container $ kill 1

Write dockerfile and build image: nginx with telnet,git

  • upper case for DIRECTIVEs

[SKIP]

  • each Directive is considered as difference in file system(RUN ADD COPY contribute to layer creation), is run in an intermediate container. notice docker build log lines: 1. running in intermediate container 2. removing intermediate container 3. using cache NOTE: Because of portability reasons, folders on host CAN'T be mounted in Dockerfile because the Dockerfile should run anywhere, it shouldnt be dependent on host.
    [SKIP]
docker build . -f-<<EOF
FROM nginx
RUN apt-get update
RUN apt-get install telnet git -y
EOF

docker build <remote context> -f-<<EOF
EOF
[TIP] remote context will always copy latest code.

BUILD

build context
docker build https://github.com/shadjachaudhari13/nodefun.git -f-<<EOF
FROM node:8
ARG PORT=8080
COPY . .
RUN npm install
ENV PORT 8080
EOF

docker run -d -p 9000:8080 6b43e2004c34 npm start

access 192.168.99.100:9000 in REST client

note build context

COPY

COPY . . will always invalidate cache if file being copied are changed. COPY src dest COPY copies files along with their permissions src is relative to Dockerfile, dest is absolute path inside container. Can't COPY from parent directory COPY ../ . is invalid. use WORKDIR to set $(pwd)

WORKDIR

sets current working directory for instructions RUN, CMD, ENTRYPOINT, COPY and ADD while building Dockerfile WORKDIR(pwd for all subsequent instructions IN Dockerfile) and build context(is where Dockerfile is) are different from each other WORKDIR will be created if not existing already, could be a blank folder too useful if the executable/artifacts you want to run when container starts are located somewhere in subdirectories not recommended to use RUN cd .. like commands keep app files in separate dir than root, avoid clutter

[build context continued..]

cd ~/Downloads
docker build . -f-<<EOF
FROM node:8
RUN git clone https://github.com/shadjachaudhari13/nodefun
WORKDIR nodefun
RUN npm install
EOF

note build context. Current directory and sub directories are set to build context. keep only required files along with Dockerfile

make changes to nodefun repository foo=bar1

cache: reuse existing layers

[run previous command twice to observe cached lines]

docker build . -f-<<EOF
FROM node:8
RUN git clone https://github.com/shadjachaudhari13/nodefun
WORKDIR nodefun
RUN npm install
EOF
``
> sample output

Sending build context to Docker daemon    125kB
Step 1/4 : FROM node:8
 ---> 1f6c34f7921c
Step 2/4 : RUN git clone https://github.com/shadjachaudhari13/nodefun
 ---> *Using cache*
 ---> 1eef8c4feaca
Step 3/4 : WORKDIR nodefun
 ---> Using cache
 ---> 28f94c66a848
Step 4/4 : RUN npm install
 ---> Using cache
 ---> ff3438c4324d
Successfully built ff3438c4324d

TIP:

  1. share code from local
  2. set remote context
  3. keep instructions that are likely to bring bring change at the end of file
  4. trick the Dockerfile!!! (add instruction that will invalidate cache at correct moment)
docker build . -f-<<EOF
FROM node:8
RUN echo $(date)>trick.log
RUN git clone https://github.com/shadjachaudhari13/nodefun
WORKDIR nodefun
RUN npm install
EOF

Push/Pull image:tag to repository

docker tag <image-id> shadjachaudhari/nodefun:mydemo
docker login
docker push shadjachaudhari/nodefun:mydemo
docker tag <image-id> shadjachaudhari/nodefun
docker push shadjachaudhari/nodefun

docker pull fetches independent layers in parallel

when tag not mentioned latest tag is applied,replaced

Use your own image as base image
docker build . -f-<<EOF
FROM shadjachaudhari/nodefun:mydemo #checks local repository first then remote. "IfNotExist PullPolicy"
RUN echo hello

VOLUME

share code repo on the host with docker container, dynamic changes to app and test quickly

store gems/requirements in volume and share such volume with app container. this way dependencies can be cached and reused while only new ones will be added/removed

VOLUME directive in dockerfile makes sure a mount point is initialized when container runs

containers can share volumes with each other

sharing data is not same as copying data into containers

Docker Compose Rises

docker compose volumes: use case: dependencies in separate container from app

git clone https://github.com/shadjachaudhari13/rubyfun.git
cd rubyfun
docker-compose -f docker-compose-v1.yaml up --build

source code shared at /rubyfun

dependency are getting installed everytime. can they be reused?

docker-compose -f docker-compose-v2.yaml up --build
docker-compose -f docker-compose-v2.yaml up --build
docker volume ls
docker images

name of docker image built by docker-compose Note: ruby image is 900mb. Lets save it offline.

docker save -o rubyfun.tar <image-id>
docker rmi -f $(docker images -q)
docker-compose -f docker-compose-v2.yaml up --build # kill process when you see layers are being pulled freshly
docker load -i rubyfun.tar
docker-compose -f docker-compose-v2.yaml up # all layers exists

ENV

Modify app dynamically using volumes: nodefun

[Dynamic update demo] (https://github.com/shadjachaudhari13/nodefun/blob/master/index.js)

https://github.com/shadjachaudhari13/nodefun.git
cd nodefun
docker-compose up --build --force-recreate
# change index.js
docker-compose up --force-recreate

##### give up sudo privilleges
[why not to run container as root](./uid-demo-Dockerfile)

sudo chmod 600 secrets.txt docker build -f uid-demo-Dockerfile --no-cache . docker run 

#### write docker compose with networks
[demo nginx with host network] (./docker-compose-nginx.yaml)
[keep changing PORT] (./default.conf)
[demo docker-compose networks] (./docker-compose-networks.yaml)
> multiple networks in one compose file
> one container can get multiple IPs as it can belong to multiple networks

#### How to build parent image? Ways to create images?
> Build from scratch: your first layer of fs

> debootstrap to tar
example https://github.com/tianon/docker-brew-ubuntu-core/blob/185c5e23efaa8c7c857683e6dcf4d886acda3cba/trusty/Dockerfile

> docker commit <container-id> shadjachaudhari/rubyfun:latest