Debug School: Gaurav Pathak

Day2- Docker Command By Gaurav Pathak

Gaurav Pathak — Thu, 27 Apr 2023 05:30:06 +0000

Some Docker Commands
• cp
• diff
• rename
• port
• update
• wait
• logs
• events
• top
• inspect
Docker commands for images
• docker images
• docker pull
• docker info
• docker rmi
• docker inspect
• docker commit – m “message” – a”name” container id alias name

Steps to create a docker images with java and apache installed
docker run -itd ubuntu
docker exec -it “containerid” /bin/bash
install java
apt-get update
apt-get install openjdk-11-jdk -y
apt-get install openjdk-11-jdk-headless -y
install apache
apt-get install apache2 -y
Install wget
apt-get install wget -y
Install war file
wget https://tomcat.apache.org/tomcat-7.0-doc/appdev/sample/sample.war
chmod 755 sample.war
commit the image
docker commit -m"my first commit" -a"gaurav" containerid name
docker images
Validate java and apache
docker exec containerid java
docker exec containerid which apache2
docker exec containerid ls /opt/

After committing to save file in tar

docker save -o image.tar name of image

To load the image which is saved as tar,

docker load -i name.tar:

Check the images using docker images command to see if the tar is loaded.
To share the image with large group we can push our image to docker repository
Create an account in docker hub
Login to docker hub
docker login
provide username and password
tag the image matching to repo name
docker tag image /gauravpathakddn/devopstraining
Push the image to repo
docker push /gauravpathakddn/devopstraining

Day3- Kubernetes Introduction by Gaurav Pathak

Gaurav Pathak — Wed, 26 Apr 2023 09:59:04 +0000

As per my initial understanding ...

What is Kubernetes?

Kubernetes is container orchestration tool for managing, automating, and scaling containerized applications. Using Kubernetes interface through GUI or kubectl , developers /devops can view ,access and deploy into container ecosystem.

Why Kubernetes?

Managing container within a data centre is complex ,rather than individually managing each container in a cluster, a DevOps team can instead use Kubernetes to allocate the necessary resources to a container in advance, and manage them effectively.

Explained Kubernetes Architecture

Kubernetes cluster has master nodes(control plane) and worker nodes.
Master node is the in charge and the worker nodes do the actual work. We can have multiple master node which are connected via a load balancer.

Master Components

API-Server – Its front door for the user who want to use Kubernetes and its services. It exposes the API(REST) and consumes JSON via manifest files.

CLUSTER STORE – It’s the persistent storage which has the information about cluster state and configuration.

CONTROLLER MANAGER – It’s a watcher within the master nodes that watch for changes and help in maintaining desired state.

SCHEDULER - It assign the work to worker nodes when asked from API Server. It watches API server for a change.

Worker Components

Kublet - It is the main Kubernetes agent. It registers nodes with clusters and instantiates pods and reports back to master.

Container Engine (Ex -Docker) – It a container management tool for pulling images and creating container.
Kube Proxy – It handle networking w.r.t to POD and also manage load balancing.

Workstation Components

It can be laptop with kubectl installed.
It can be web based UI.
Text Editor or IDE.

What is POD?

A pod is the smallest execution unit in Kubernetes.
POD contains one or multiple containers.
POD communicate over pod network to each other
POD is IP addresses and abstract the container running inside them For ex- container 1 -> port 80 , container 2 -> port 90 . IP Address for POD – 10.10.2.2 Then to access container1 address will be 10.10.2.2:80
If a pod fails, it cannot be redeployed. A pod can only be created.
PODs are having three stages – Pending , Running, Success/Failed

Day 1 Docker - Assignment- By Gaurav Pathak

Gaurav Pathak — Mon, 24 Apr 2023 17:55:01 +0000

What is Docker?

Docker is a container management tool. It allow developers ,admins etc. to easily deploy their application in a container.

Why We need docker?

Docker allows you to instantly create and manage containers with ease, which facilitates faster deployments. Also when compared with Physical Server/Virtual server, docker help us in cutting cost, saves time and improve software development quality. It provides a complete application isolation by provisioning container on fly within few seconds.

What is Container?

A container is a runtime instance of a Docker image.

How Container Works?

Containers bundle the application along with its dependency packages. It kind of providing a standalone environment to run the specific application.

How to install Docker?

We can use below scripts to install docker.
Step 1 – Download and Run the script.
$ curl -fsSL get.docker.com -o get-docker.sh
$ sudo sh get-docker.sh
Step 2 – Enable Docker
$ sudo systemctl enable docker
Step 3 – Start Docker
$ sudo systemctl start docker

What are the components of docker?

Docker Engine (Docker Client + DockerD)
Docker Images
Docker Registry
Container

What is a container lifecycle commands?

docker create image(httpd)
docker start containerId
docker stop container nameorId
docker restart
docker pause
docker unpause
docker kill ex:- docker kill containerId
docker remove ex:- docker rm containerId

What is docker pause/unpause?

The docker pause command is used to suspend all processes in the specified containers.
The docker unpause command un-suspends all processes in the specified containers.

What is docker stop/kill?

Docker stop command sends SIGTERM signal to running container process.
Docker stop command will gracefully terminate the container making sure that all child process will gracefully end up before container will shutdown. It return process exited code as 0 upon successful termination.

Docker kill command is kind of similar to docker stop command however it sends SIGKILL signal to our running container process. SIGKILL signal immediately shuts the container down without taking any pause.

How to get inside a container?

We can get inside a container using SHELL.
We can use docker exec command. This will let us to run arbitrary commands inside an existing container. Ex - docker exec 6d77829ff395 ps -eaf .
6d77829ff395 - Container Id for an ubuntu container.
To exec command in interactive mode we can use command
docker exec -it 6d77829ff395.

How to access container from outside?

To access container from outside we need NETWORK.
Use docker inspect command to get container IP address and follow the below steps
docker inspect 955a249cbf71
docker ps
curl http://172.17.0.9
ping "172.17.0.9"

What is the rule for container is running?

Container is running AS LONG AS PID1 is running Anything