Changing the default process of the container
- Remove all Docker containers and images. …
- Stop the Docker service. …
- Remove the Docker storage directory. …
- Create a new /var/lib/docker storage directory. …
- Use bind mount to set the new location. …
- Start the Docker service.
Ex: Create a dockerfile, for using ubuntu as base image, and install java in it.
Download jenkins.war and make execution of “java -jar jenkins.war” as the default process.
Every docker image come with default process.
As long as default process is running, the container will be running condition.
The moment, the default process is closed, the container will be exited.
Lets remove all the container
# docker rm -f $(docker ps -aq)
When we start ubuntu container, we use below command
# docker run –name c1 -it ubuntu
To comeout of the container we use Ctrl + p + q
# docker container ls
( our container c1 is running in the background )
When we start jenkins container, we use below command
# docker run –name j1 -d -P jenkins/jenkins
Now, I want to open interactive terminal to enter jenkins
# docker exec -it j1 bash
( In ubuntu container, I can directly go into -it terminal,
where as in jenkins i am running an additional command exec ? )
Lets try to go to interactive terminal in docker run command )
# docker run –name j2 -it jenkins/jenkins
( we are not getting interactive terminal )
I want to run tomcat as container
# docker run –name t1 -d -P tomee
Lets find the reason
docker container ls ( to see the list of containers )
Observer the command section.
It tells you the default process that gets executed, when we start the container.
Container Default process
bash — is nothing but the terminal.
For linux based container, the default process is shell process
( ex of shell process are bash shell, bourne shell etc )
Hence we are able to enter -it mode in ubuntu )
We are trying to change the default process of the container.
# vim dockerfile
RUN apt-get update
RUN apt-get install -y default-jdk
Build an image from the dockerfile
# docker build -t myubuntu .
TO see the list of images ( we can see our new image )
# docker image ls
TO start container from new image
# docker run myubuntu ( Observe the logs generated on the
screen, we got logs related to jenkins , jenkins is fully up and running )
Its an ubuntu container, it is behaving as a jenkins container )
RUn the below command
# docker ps -a
For myubuntu the command is java -jar jenkins.war
For ubuntu the commans is /bin/bash
Working on docker registry
Registry is a location where docker images are saved.
Types of registry
1) public registry
2) private registry
public registry is hub.docker.com
Images uploaded here are available for everyone.
Usecase: Create a customized ubuntu image, by installing tree in it.
Save this container as an image, and upload this image in docker hub.
Step 1: Create a new account in hub.docker.com
Step 2: Creating our own container
# docker run –name c5 -it ubuntu
Lets install tree package in this container
/# apt-get update
/# apt-get install tree
Step 3: Save the above container as an image
# docker commit c5 sunildevops77/ubuntu_img26
( sunildevops77/ubuntu_img15 — is the image name )
Note: Image name should start with docker_id/
To see the list of images
# docker image ls ( we can see the new image )
TO upload the image to hub.docker.com ( docker login command is used )
# docker login ( provide docker_id and password )
To upload the image
# docker push <image_name>
# docker push sunildevops77/ubuntu_img26
login to docker hub to see your image
This is the process of running docker containers in a distributed environment, on multiple docker host machines.
All these containers can have a single service running on them and they share the resources between each other, even running on different host machines.
Docker swarm is the tool used for performing container orchestration
1) Load balancing
2) scaling of containers
3) performing rolling updates
4) handling failover scenarios
Machine on which docker swarm is installed is called as manager.
Other machines are called as workers.
Lets create 3 machines
Name is as Manager, Worker1, Worker2
All the above machines should have docker installed in it.
Install docker using get.docker.com
( Optional step to change the prompt )
After installing docker in the 1st machine ( Manager ), Lets change the host name.
Host name will be available in the file hostname. We will change the hostname to manager.
# vim /etc/hostname
After changing the hostname, lets restart the machine
# init 6
Similary repeat the same in worker1 and worker2
Connect to Manager, install docker swarm in it.
$ sudo su –
Command to install docker swarm in manager machine
# docker swarm init –advertise-addr private_ip_of_manager
# docker swarm init –advertise-addr 172.31.42.135
Please read the log messages
Now, we need to add workers to manager
Copy the docker swarm join command in the log and run in the worker1 and worker2
Open another gitbash terminal, connect to worker1
sudo su –
# docker swarm join –token SWMTKN-1-27lf3n7xxqy2u3gb61mvfybk51uqjq9hj4m5uwdd4lcgtgafth-0hmrtwzrcyqv4h7cl3euekq68 172.31.44.50:2377
Repeat for worker2
TO see the no of nodes from the manager
Manager # docker node ls ( we can see manager, worker1 and worker 2)