Debug School: Satish

Day 2 - Docker commands

Satish — Wed, 26 Apr 2023 09:56:08 +0000

*Executed some more Docker commands *
Docker Commands – First Commands
Command Description
info Display system-wide information
version Show the Docker version information
Docker Commands – Working with Containers
Command Description
attach Attach local standard input, output, and error streams to a running container
cp Copy files/folders between a container and the local filesystem
create Create a new container
diff Inspect changes to files or directories on a container’s filesystem
exec Run a command in a running container
inspect Return low-level information on Docker objects
kill Kill one or more running containers
pause Pause all processes within one or more containers
port List port mappings or a specific mapping for the container
ps List containers
rename Rename a container
restart Restart one or more containers
rm Remove one or more containers
run Run a command in a new container
start Start one or more stopped containers
stop Stop one or more running containers
unpause Unpause all processes within one or more containers
update Update configuration of one or more containers
wait Block until one or more containers stop, then print their exit codes
Docker Commands – Monitoring Containers
Command Description
logs Fetch the logs of a container
ps List containers
stats Display a live stream of container(s) resource usage statistics
top Display the running processes of a container
events Get real time events from the server
Docker Commands – Working with Image
Command Description
build Build an image from a Dockerfile
commit Create a new image from a container’s changes
export Export a container’s filesystem as a tar archive
history Show the history of an image
images List images
import Import the contents from a tarball to create a filesystem image
inspect Return low-level information on Docker objects
load Load an image from a tar archive or STDIN
rmi Remove one or more images
save Save one or more images to a tar archive (streamed to STDOUT by default)
tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
Docker Commands – Working with Registry/Repository
Command Description
login Log in to a Docker registry
logout Log out from a Docker registry
pull Pull an image or a repository from a registry
push Push an image or a repository to a registry
search Search the Docker Hub for images
Docker Commands – Management Commands
Command Description
config Manage Docker configs
container Manage containers
image Manage images
network Manage networks
node Manage Swarm nodes
plugin Manage plugins
secret Manage Docker secrets
service Manage services
swarm Manage Swarm
system Manage Docker
trust Manage trust on Docker images
volume Manage volumes
Docker Cheatsheet
Build docker image
$ cd /path/to/Dockerfile
$ sudo docker build .
View running processes

$ sudo docker ps
View all processes

$ sudo docker ps -a
Run an image in a new container daemonized

$ sudo docker run -d
Run an image in interactive mode with the command /bin/bash

$ sudo docker run -i -t /bin/bash
Run an image in interactive mode with the command /bin/bash and link the ports.

$ sudo docker run -i -t --link : /bin/bash
Run an image with an ENTRYPOINT command in interactive mode with the command /bin/bash

$ sudo docker run --entrypoint /bin/bash -i -t
Run an image in interactive mode with the command /bin/bash mounting the host director /var/app/current to the container directory /usr/src/app

$ sudo docker run -i -t -v /var/app/current:/usr/src/app/ /bin/bash
Run an image in interactive mode with the command /bin/bash setting the environments variables FOO and BAR

$ sudo docker run -i -t -e FOO=foo -e BAR=bar /bin/bash

• docker commit – m “message” – a”name” container id alias name

*How to design docker image *
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"message" -a"satish" containerid name
docker images
Validate java and apache
docker exec containerid java
docker exec containerid which apache2
docker exec containerid ls /opt/
Saving and loading tar file
After committing the docker image
Save the file
docker save -o image.tar name of image
you can stop the containers if u want
Load the file
docker load -i image.tar
Pushing the docker image to repository
Create an account in docker hub
Login to docker hub in putty
docker login
provide username and password
tag the image matching to repo name
docker tag image sati1241/satishdevops
Push the image to repo
docker push sati1241/satishdevops

Day -1 Dockers realted questions.

Satish — Wed, 26 Apr 2023 09:29:27 +0000

What is Docker?

Docker is a set of platform as a service products that use OS-level virtualization to deliver software in packages called containers. The service has both free and premium tiers. The software that hosts the containers is called Docker Engine.
Why We need docker?

Because Docker containers encapsulate everything an application needs to run (and only those things), they allow applications to be shuttled easily between environments.
Docker enables more efficient use of system resources. Instances of containerized apps use far less memory than virtual machines, they start up ...

What is Container?
A container is a unit of software that packages code and its dependencies so the application runs quickly and reliably across computing environments.

How Container Works?

Containers are an abstraction in the application layer, whereby code and dependencies are compiled or packaged together. It is possible to run multiple containers on one machine. Each container instance shares the OS kernel with other containers, each running as an isolated process.
How to install Docker?

You can download and install Docker on multiple platforms. Refer to the following section and choose the best installation path for you.
What are the components docker?

You can download and install Docker on multiple platforms. Refer to the following section and choose the best installation path for you.
1 Docker Installation in Centos/RHEL
1.1 Method -1: How to install Docker Community Edition via YUM?
1.2 Method – 2: How to install Docker Community Edition via RPM Packages?
1.3 Method – 3: How to install Docker Community Edition via script?
2 Docker install in Ubuntu
3 How to Install Docker in RHEL8 / RHEL9 / CENTOS8 / CENTOS9?
I used the below method
Docker provides convenience scripts at get.docker.com.
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
Step 4 – Verify that docker is installed correctly by running the hello-world image.

$ sudo docker run hello-world

What is a container lifecycle commands?

CREATE -> START -> STOP -> START -> RESTART -> PAUSE -> UNPAUSE -> KILL -> REMOVE
What is docker pause/unpuase?

Paused / Unpaused state
So, as the container is running, there must be a way to pause it. We can do so by running the pause command. This command effectively freezes or suspends all the processes running in a container. When in a paused state, the container is unaware of its state.

docker pause container

It basically sends the SIGSTOP signal to pause the processes in the container.

Similarly, to get the paused container back on running, we’d use the docker unpause command:

docker unpause container

What is docker stop/kill?

For a container to be in a killed state, we run the docker kill command, which sends SIGKILL signals to terminate the main process immediately. This means the difference between docker stop and docker kill is that - stop can allow safe termination (within the grace period) while kill terminates immediately.
How to get inside a container?

Once you have your Docker container up and running, you can work with the environment of the Docker container in the same way you would do with an Ubuntu machine. You can access the bash or shell of the container and execute commands inside it and play around with the file system. You can build, test, and deploy your applications inside the container itself.
Predominantly, there are 3 ways to access the shell of a running container. These are -

Using the Docker run command to run a container and access its shell.
$ docker run -it --name=myubuntu ubuntu:latest bash
Using the Docker exec command to run commands in an active container.
$ docker exec [OPTIONS] CONTAINER COMMAND [ARG...]
$ docker exec -it myubuntu bash

Using the Docker start command and attach a shell to a stopped container.

$ docker start [OPTIONS] CONTAINER [CONTAINER...]
$ docker container ps -a
$ docker start -ai myubuntu

How to access container from outside?

In order to make a port available to services outside of Docker, or to Docker containers which are not connected to the container's network, we can use the -P or -p flag. This creates a firewall rule which maps a container port to a port on the Docker host to the outside world.
Accesss from Outside === Network

65 docker inspect 955a249cbf71
66 docker ps
67 curl 172.17.0.9
68 ping "172.17.0.9"
69 history

What is the rule for container is running?

The docker run command first creates a writeable container layer over the specified image, and then starts it using the specified command.
To check the status of a specific container you can use the docker ps command to list all running containers and filter them using grep to show the specific container you're interested in.

Day -3 related to Kubernetes

Satish — Wed, 26 Apr 2023 09:28:22 +0000

What is Kubernetes?

Kubernetes is an open-source container orchestration system for automating software deployment, scaling, and management. Originally designed by Google, the project is now maintained by the Cloud Native Computing Foundation.

Kubernetes is a portable, extensible, open source platform for managing containerized workloads and services, that facilitates both declarative configuration and automation. It has a large, rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.

Kubernetes is an open-source container orchestration system for managing, scaling, and automating software deployment. Kubernetes helps organizations with DevOps, as it combines the development and maintenance phase of software systems to improve agility. Through the Kubernetes user interface, developers can view, access, deploy, update, and optimize container ecosystems.

Why Kubernetes?
Kubernetes provides you with a framework to run distributed systems resiliently. It takes care of scaling and failover for your application, provides deployment patterns, and more. For example: Kubernetes can easily manage a canary deployment for your system.

Essentially, containerization is an efficient and effective way to implement DevOps than a monolithic application. Kubernetes creates and manages containers on the cloud-based server systems. Kubernetes helps DevOps teams to reduce the burden of infrastructure by letting containers operate on different machines/environments without breakdowns.

Explained Kubernetes Architecture ?

An environment running Kubernetes consists of the following basic components: a control plane (Kubernetes control plane), a distributed key-value storage system for keeping the cluster state consistent (etcd), and cluster nodes (Kubelets, also called worker nodes or minions).

TABLE OF CONTENTS
Kubernetes Architecture
Control Plane
Worker Node
Kubernetes Control Plane Components

kube-apiserver
etcd
kube-scheduler
Kube Controller Manager
Cloud Controller Manager (CCM) Kubernetes Worker Node Components
Kubelet
Kube proxy
Container Runtime Kubernetes Cluster Addon Components
CNI Plugin

Master Components?
etcd. It stores the configuration information which can be used by each of the nodes in the cluster. ...
API Server. ...
Controller Manager. ...
Scheduler. ...
Docker. ...
Kubelet Service. ...
Kubernetes Proxy Service.

Worker Components?
Worker nodes within the Kubernetes cluster are used to run containerized applications and handle networking to ensure that traffic between applications across the cluster and from outside of the cluster can be properly facilitated.

The components on a node include the kubelet, a container runtime, and the kube-proxy.

Workstation Components?

Kubernetes automates operational tasks of container management and includes built-in commands for deploying applications, rolling out changes to your applications, scaling your applications up and down to fit changing needs, monitoring your applications, and more—making it easier to manage applications.

A Kubernetes cluster consists of the components that are a part of the control plane and a set of machines called nodes.

What is POD?
A pod is the smallest execution unit in Kubernetes. A pod encapsulates one or more applications. Pods are ephemeral by nature, if a pod (or the node it executes on) fails, Kubernetes can automatically create a new replica of that pod to continue operations.

A pod is the smallest execution unit in Kubernetes. A pod encapsulates one or more applications. Pods are ephemeral by nature, if a pod (or the node it executes on) fails, Kubernetes can automatically create a new replica of that pod to continue operations.