1. docker container can be find / downloaded from docker hub / docker store.
http://hub.docker.com
i.e
$docker run ansible
$docker run mogodb
$docker run redis
$docker run nodejs
2. Docker have two addition
i. Community Edition
ii. Enterprise Edition
3. Community Edition are availble for mac/windows/cloud (AWS)
4. Install docker desktop for windows / mac from http://docs.docker.com/install
5. It will be eaiser to install docker through convenience script, instruction must be found on http://docs.docker.com/install
6. Download images/container from http://hub.docker.com
7. To test visit the hub.docker and search for whalesay image to test the docker installation.
$sudo docker run docker/whalesay cowsay HelloWorld
Docker will pull the image and runs it.
8. Docker Command
i. $docker run <<container-name>> : to run the image, the image will be downloaded if not available.
ii. $docker ps : will list all the containers
-a : show the status and other details
iii. $docker stop <<container-name>>
iv. $docker rm <<container-name>> : remove the installed docker.
v. $docker images : list down the downloaded images.
vi. $docker rmi <<image-name>> : to remove the downloaded image.
a. Stop and delete all the dependent container to remove image.
vii. $docker pull <<image-name>> : just to pull the image without running it.
viii. $docker run ubuntu : to run the container
ix. $docker ps -a : list down the running container.
x. Why the containers are in Exited status?
Containers are ment to run process / tasks /webserer / application server/database instance not operating system once the task / process is completed the container exists.
$docker run ubuntu sleep 5 : the ubuntun imaghe will start and sleep for 5 seconds one the task is completed the ubuntu iamge will be in Existed.
xi. $docker exec distracted_mcclintock cat /etc/hosts : execute command inside the container to display the file content.
xii. Processes runs either on four ground / active mode.
a. $docker run kodekloud/simple-webapp : Run the image on attached mode.
b. $docker run -d kodekloud/simple-webapp : Run the image in detach mode (backgroundm ode).
- $kdocker attach <<image-name>> / <<image-id>> : to connect the detach container run the following command
- first five character of docker image id are enough to run any docker command.
ix. $docker run redis : to run the latest redis server
$docker run redis:4.0 : to run the older version redis use the tag, the tag can be used with any image.
xx. The hub.docker.com listdown all the versions / tags for all the available images.
xxi. $docker run -i my/simple-prompt-docker : where -i is for an interactive mode to receive command line input and pass as parameter in application.
$docker run -it my/simple-prompt-docker : for more interactive mode where you will see the application asking for input and you need to type you value and application will process that input further.
xxii. Port forwarding:
$docker run my/webapp: to start the web application image, the webapp is running on 5000 port (i.e http://172.17.0.2:5000/). Every machine have default IP and only accessable from docker host and not accessable outside the host.
$docker run -p 80:5000 my/webapp : Map the port to access docker webapp image instance running on 5000 port.
- this way you can run multipule instance of application using different ports.
i.e
$docker run -p 8000:5000 my/webapp
$docker run -p 9000:5000 my/webapp
$docker run -p 3306:3306 mysql
$docker run -p 8306:3306 mysql
$docker run -p 9306:3306 mysql
- all above host ports are forwarded to one post of docker image.
xxiii. Volume Mapping
i.e $docker run mysql
$docker stop mysql
$docker rm mysql
Onec the container removed all the data inside mysql database will be removed as well to prevent this we need to map the mysql data files with host file path.
$docker run -v /opt/datadir:/var/lib/mysql mysql
one the container starts with volume mapping all the data will be stored in the host system. Removing the mysql container will not effect the stored data.
xxiv. Inspect Container:
$docker inspect <<container-name>> : will return the json contain the details about container.
xxv. Container logs (Processing running in detach mode)
$ docker logs <<container-name>>
xxvi. Set Environment Variables:
The environment varabiles can be used inside the application and to set those run the following command:
$docker run -e APP_COLOR=blue myweb
$docker run -e APP_COLOR=red myweb
$docker run -e APP_COLOR=green myweb
to view the envrionment variable of container use inspect command
$docker inspect <<container-name>>
You will find the list of ENV in config tag of josn returned by inspect command.
9. Free lab to prectise the lab and quiz http://kodekloud.com/p/docker-labs
10. Create your own docker image.
- Task list
i. Install OS (ubuntu)
ii. Update apt repository
iii. Install apt updates
iv. Install the python and its dependencies
v. Copy the source
vi. Run the application
- Process
i. Create docker file 'Dockerfile' and put all the commands are you will execute on OS.
i.e
--------------------------------
FROM Ubuntu
RUN apt-get update
RUN apt-get install python
RUN pip install flask
RUN pip install flask-mysql
COPY ./opt/source-code
ENTRYPOINT FLASK_APP=/opt/source-code/app.py flask run
----------------------------------
- In the above file, everything on left (i.e FORM, RUN, COPY) are instruction and text on the right side are Argument.
-FROM Ubuntu: deifne the base OS required for docker image.
ii. Build you image with docker build command using Dockerfile as parameter.
$docker build Dockerfile -t isyed/my-python-app
or
$docker build .
- If you want to re-run / contine if the building image failed on any step.
iii. Run the push command to push the newly created image to public hub docker repository.
$docker push isyed/my-python-app
- here isyed is my account name which is created on docker website.
$docker history isyed/my-python-app
- to know the history and size of container image.
