Docker In Details

 

Course Contents:-

1. Overview of Docker
2. Difference between Virtualization & Containerization
3. Installation & Configuration of Docker Runtime on Linux & Windows
4. Practice on Docker commands
5. launch a Webserver in a container
6. Launch public & official images of application like Jenkins, Nginx, DB etc..
7. Launch a base OS Container
8. How to save changes inside the container & create a fresh image(commit)
9. How to ship image & container from one hardware to another.
10. How to remove stop/rm multiple container/images
11. Docker Registry

12. Docker Networking
      Check current docker network         
      Docker Network Bridge            
      Docker Network Weaving         
      Launch our own Docker Cluster with our defined Network          
      Launch containers in our own isolated network 

13. Dockerfile
      Importance of Dockerfile
      How to write Dockerfile
      How to build Dockerfile
      How to launch containers using Dockerfile
      How to export Dockerfile to CI tool      

  14. Docker-compose      How to launch fleet of docker containers using docker-compose

Getting started

https://docs.docker.com/docker-for-windows/install/

Install Docker on RHEL based VM

1. yum update -y
2. yum install docker -y
3. systemctl start docker
4. systemctl status docker
5. ifconfig

Commands

To list docker version

docker --version

To list running containers

docker ps

To list all stopped/terminated/Exited containers
docker ps -a

To pull image
docker pull "image_name"

To run a container in interactive mode

once you existed the container will terminate.
docker run -it image_name --name=name of your container   process(bash)
ex: docker run -it --name="container_name" "image_name" bash

To run container for long time.

docker run -itd --name=my-<container name> <image name> bash

To remove all stopped containers from the list ex docker ps -a
docker rm $(docker ps -a -q)

To list images

docker images

to find images in local machine

cd /var/lib/docker/

To remove image
docker rmi -f imagename

To go inside a running container
docker exec -it "container_id/container_name" bash

To save changes from container to image
docker commit "container_id" image_name

pull httpd image:

docker pull httpd

Or

docker run -itd --name webserver  httpd

docker images

docker ps 

curl -kv http://localhost:80

docker stop <httpd container id>

docker run -dit --name <container name> -p 8080:80 <httpd>

docker ps 

curl -kv http://localhost:80

browse with public ip and port

docker exec -it <container name> bash

ls htdocs/index.html

cat htdocs/index.html

docker run -dit --name my-web-server  -p 8090:80 httpd

to list container files without logging into container

docker exec <container name>  ls -l

Docker Commit:

docker run -itd --name my-centos centos:latest

docker ps

docker exec -it my-centos bash

yum install httpd -y

ls /var/www/html

mkdir /tmp/imperial

exit

docker ps 

docker images

docker commit <container name> my-new-centos:v1.0

docker images

docker run -itd --name my-new-web  -p 9999:80 mycentos:v1.0 /usr/sbin/httpd -D FOREGROUND 

docker ps

browse with public ip

login to container

go to document root /var/www/html

create index.html with content

and refresh browser

Docker Volume:

go to efs location 

cd /tmp/myefs/myworkspace

ls myworkspace/my_scripted_pipeline/webapp/target/webapp

mkdir docker-volume

cp -rf myworkspace/my_scripted_pipeline/webapp/target/webapp docker-volume/

ls docker-volume

docker images

docker run -itd --name my-con-with-vol -v /tmp/myefs/docker-volume/:/var/www/html -p 8888:80 mycentos:v1.0 /usr/sbin/httpd -D FOREGROUND

browse from browser with 8888

docker exec -it my-con-with-vol ls /var/www/html

Check docker container log

docker logs <container id>

To save the current image to ship it to another device or hardware
docker save "image name" > "my_image_name".tar

To load the above image back to container after shipping
docker load < "my_image_name".tar

To export the running container to another hardware or device with existing configuration
docker export "container_name" > "my_export_image".tar

To import the container
docker import  - "new_image_name" < my_export_image.tar

Create container out of imported image.

docker run -itd --name=<container name> <Image name> bash

To push docker image to your Docker Hub Account.
Initially,

docker login

docker tag imagename yourdockerusername/imagename:tag

docker push yourdockerusername/imagename:tag

To mount volume on containers -v source:destination
docker run -itd --name=container_name -v /tmp/webapp:/var/www/html image_name

To list container file system from Host
docker exec "container_id" command
ex:- docker exec container_id ls /tmp/data0

or

docker exec container_id cat /etc/passwd

To see docker network
docker network ls

to see network information of the containers
docker network inspect bridge

To create out own network
docker network create --driver=bridge --subnet=192.168.2.0/24 "your_network_name"

To check our network
docker network inspect drivername
ex:- docker network inspect "your_network_name" (network name or network id)

To launch container in our network
docker run -itd --network=my_network --name=myweb -p 9999:80  httpd_image:aamirs /usr/sbin/httpd -D FOREGROUND

or

docker run -itd --network=my_network --name=mytest_conatiner centos

To delete a network
docker network rm "network_id or network_name"


To create a docker Private Registry for docker images
https://docs.docker.com/registry/deploying/#run-a-local-registry

To list docker information
docker info

To list docker system info
docker system df

or

docker system df -v

To list docker Statistics
docker stats "container_id"

To find list of Docker commands
docker --help

To find docker volume mount point information on a container
docker inspect -f "{{ .Mounts }}" container_id

To grep only Mounts from above command
docker inspect -f "{{ json .Mounts }}" container_id | jq

or

docker inspect -f "{{ json .Mounts }}" container_id | python -m json.tool

To find history of docker images
docker history image_name

To find all the information about a container
docker inspect container_id

How to create docker volume
docker volume create "volume_name"

by default it will be created under /var/lib/docker/volumes

If we wish to change default volume location, we change it in below file & restart docker service
ls /lib/systemd/system/docker.service

https://stackoverflow.com/questions/36014554/how-to-change-the-default-location-for-docker-create-volume-command

check

docker volume ls

ls /var/lib/docker/volumes

These volumes can also mounted to a container

docker run -itd -v "your_volume_name":/tmp image_name


Docker Daemon logs
Below command will log docker logs only in RHEL based VM's , Other OS may have different location to log the docker logs.

cat /var/log/messages | grep docker

Docker container logs

cat /var/lib/docker/containers/<container_id>/<container_id>-json.log

Container config info files

cat /var/lib/docker/containers/container_id/config.v2.json

cat /var/lib/docker/containers/container_id/hostconfig.json

========================

Dockerfile

https://gitlab.com/Azam-devops/webserver-docker

https://gitlab.com/Azam-devops/docker-jenkins

Difference between Entrypoint & CMD & RUN command with examples

Entrypoint  Shell Form & Exec Form

• RUN executes command(s) in a new layer and creates a new image. E.g., it is often used for installing software packages.
• CMD sets default command and/or parameters, which can be overwritten from command line when docker container runs.
• ENTRYPOINT configures a container that will run as an executable.

Shell form
<instruction> <command>

 

ENV name John Dow ENTRYPOINT echo "Hello, $name"

docker run -it <image>

Exec form

This is the preferred form for CMD and ENTRYPOINT instructions.

<instruction> ["executable", "param1", "param2", ...]

ENV name John Dow

ENTRYPOINT ["/bin/echo", "Hello, $name"]

docker run -it <image>

ENV name John Dow

ENTRYPOINT ["/bin/bash", "-c", "echo Hello, $name"]

docker run -it <image>

RUN has two forms:

• RUN <command> (shell form)
• RUN ["executable", "param1", "param2"] (exec form)

CMD has three forms:

• CMD ["executable","param1","param2"] (exec form, preferred)
• CMD ["param1","param2"] (sets additional default parameters for ENTRYPOINT in exec form)
• CMD command param1 param2 (shell form)

CMD echo "Hello world"

docker run -it <image>

 

docker run -it <image> /bin/bash

 

ENTRYPOINT has two forms:

• ENTRYPOINT ["executable", "param1", "param2"] (exec form, preferred)
• ENTRYPOINT command param1 param2 (shell form)

ENTRYPOINT ["/bin/echo", "Hello"]

CMD ["world"]

docker run -it <image>

docker run -it <image> John

• CMD echo “Hello World” (shell form)
• CMD ["echo", "Hello World"] (exec form)
• ENTRYPOINT echo "Hello World" (shell form)
• ENTRYPOINT ["echo", "Hello World"] (exec form)

 Example Dockerfile for testing all above commands--- >

FROM centos:latest
#ENV name John Dow
#ENTRYPOINT echo "$name"

#ENV name John Dow
#ENTRYPOINT ["/bin/echo", "Hello, $name"]

#ENV name Aamir
#ENV var1 Shaikh
#ENTRYPOINT ["/bin/bash", "-c", "echo Hello, $name, $var1"]

#CMD echo "Hello world"

#ENTRYPOINT ["/bin/echo", "Hello"]
#CMD ["world"]

#CMD ["/bin/ping", "localhost"]
========================

To create a Dockerfile.
Refer gitlab https://gitlab.com/andromeda99/webserver-docker link
create a docker file on any location

To run a dockerfile
run a dockerfile where you create it.
docker build -t "new_image_name"  .

To launch webserver using above link
docker run -itd --name=web1_mywebserver -p 8888:80 "new_image_name"

Now launch in your own network & mount volume
docker run -itd -v /tmp/webapp:/var/www/html/ --name=container_name --network=your_network_name -p 9999:80 image_name

How to check the value of an environment variable in a container

docker exec my_testwebserver  bash  -c 'echo $DocumentRoot'

Docker Compose
https://gitlab.com/andromeda99/docker_compose

https://docs.docker.com/compose/install/

Some Useful links:-
https://docs.docker.com/registry/deploying/#run-a-local-registry

https://gitlab.com/andromeda99/webserver-docker.git

https://stackoverflow.com/questions/30133664/how-do-you-list-volumes-in-docker-containers

https://goinbigdata.com/docker-run-vs-cmd-vs-entrypoint/

https://stackoverflow.com/questions/30969435/where-is-the-docker-daemon-log

https://sematext.com/blog/docker-logs-location/

https://docs.docker.com/engine/reference/commandline/volume_ls/

https://stackoverflow.com/questions/28722548/updating-path-environment-variable-permanently-in-docker-container/38905161

https://www.aelius.com/njh/subnet_sheet.html

https://phoenixnap.com/kb/ansible-check-if-file-exists