What is Docker

  • By
  • March 2, 2022
  • Docker

What is Docker –

  • Docker is a Open-Source centralized platform management tool. Docker is one of the most popular tool as compare with other comparative tools for manage containers.
  • Docker is easiest way to create, deploy and run application on containers.
  • Docker use a container to manage OS to run any application, container is access system resources form the Linux Kernel instead of allocation fix hardware like virtual machine. docker run natively on Linux distributions, so better  performance and result always recommended to use docker on any linux OS.
  • Docker application tool written in “go” programming language, which is initially develop for the write programs for the network infrastructure management.
  • Docker tool create OS level virtualization, that we well known as a containerization.
  • Docker solve so may real environment issues of developer to run application on various platform, lightweight solutions system admin, better resource management system for virtualization with container etc.
  • Docker was developed by Solomon Hykes and Sebastien Pahl, it was release in March 2013.
  • Docker is Platform As a Service that provide OS level virtualization.

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Docker Container –

  • Container is similar like Virtual Machine to setup OS
  • It hold the all required or dependency packages to run any application.
  • Docker run application on container 
  • Docker container is lightweight solution for our virtualization requirement.
  • We can easily convert container into image and send to others.
  • Once docker run that image it convert into container.

 

Advantages of Docker –

  • Docker take very less time to create container 
  • Docker does not allocate the fix resources of host system
  • It is one of best light weight solution for virtualization
  • Less cost
  • It can implement of Physical hardware, Virtual Hardware (machine) and in cloud base system also work sufficiently.
  • We can re-use the image as per requirement
  • Rebuild new images easy process
  • Very less time required to stop or start container

 

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Steps for Dockers Management –

Use OS: amazon ami linux 2 

Step1:

First verify you have docker installed or not

#docker    –version

Or

#rpm   -q    docker

 

Step2:

To install docker use following command

#yum   update   -y

#yum    install    docker   -y

 

Step3:

Now again verify docker successfully installed or which version you is installed

#docker    –version

To check where store the docker files

#which   docker

Strep4:

For show docker service status

#systemctl   status  docker

 

To start docker service

#systemctl   start  docker

For permanent on docker service ( each boot start )

#systemctl   enable docker

Strep5:

For pull ubuntu image from docker hub

#docker   pull   ubuntu

#docker   pull   centos

Strep6:

For show docker images

#docker  images

Strep7:

For start docker image into container

#docker   run   -it   ubuntu    /bin/bash

For check ubuntu version

root@cid# cat   /etc/os-release

root@cid# ls

For exit container (stop)

root@cid# exit

Strep8:

For show running docker process

#docker   ps

For show runnning and stop docker process

#docker   ps    -a

Strep9:

if we want to login into existing container

#docker   ps   -a

#docker   start    indian_angel

For go inside into docker

#docker   attach   indian_angel

root@cid# ls

root@cid# exit

Step10:

For remove existing container (stop container)

#docker   ps   -a

#docker   rm    indian_angel

#docker   ps   -a

Step11:

For remove docker images

#docker   images

#docker   rmi    Ubuntu

Step12:

For start container with customization name

#docker   run  -it   –name   testcon   ubuntu   /bin/bash

Step13:

Create content inside the container

#mkdir /aaa

#mkdir /red

#touch  /aaa/note{1..5}.txt

#exit

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Step14:

To check difference between ubuntu original image and new create testcon container image

 

#docker    diff   testcon

C /root

A /root/.bash_history

A /red

A /aaa

A /aaa/note4.txt

A /aaa/note5.txt

A /aaa/note1.txt

A /aaa/note2.txt

A /aaa/note3.txt

 

Note:

C: changes

A: add (addition)

 

Step15:

For create new self image of testcon container

#docker   commit    <container-name>   <new-image-name>

#docker   commit    testcon   testimage

 

Step16:

For create container from new created image

#docker   run   -it   –name   testimagecon   testimage /bin/bash

#ls  /aaa

For create container from Docker

  1. Create docker file

#vim   Dockerfile

#vim   Dockerfile

FROM Ubuntu

RUN echo “welcome to docker”  >  /home/welcome.txt

:wq

 

  1. To create image of dockerfile

#docker    build   -t   myimage  .

#docker   ps   -a

#docker    images

 

  1. for start new created docker image

#docker   run   -it   –name   myicon   myimage  /bin/bash

#cd /home

#cat   welcome.txt

#exit

 

now, create new Dockerfile(update existing)

 vim Dockerfile

#vim Dockerfile

#ls

#cat > testfile1

#docker build -t myimage1.

#docker images

#docker run -it –name myicon1 myimage1 /bin/bash

#pwd

#ls

#exit

 

Steps For Manage Docker Volume:

For pull ubuntu image from docker hub

#docker   pull   ubuntu

#docker   pull   centos

 

For show docker images

#docker images

For volume

step1: 

For create docker file

#vim   Dockerfile

FROM ubuntu

VOLUME [“/mydata”]

:wq

 

step2:

For build docker image

#docker build  -t  myimage  .

For show docker image

#docker images

 

step3:

create container from myimage

#dcoker  run  -it   –name  con1   myimage   /bin/bash

root@cid# ls

root@cid# cd    /mydata

root@cid# ls

root@cid# touch   con1{a..e}.txt

 

step4:

For share volume (/mydata) with new container

#docker  run  -it   –name  con2  –privileged=true    –volumes-from   con1    ubuntu   /bin/bash

root@cid# ls

root@cid# cd    /mydata

root@cid# ls

root@cid# touch   con2{a..e}.txt

root@cid# ls

root@cid# exit

 

Step5:

Start container con1 and verify con2 created data available or not

#docker   ps   -a

#docker   start   con1

#docker    attach  con1

root@cid# ls

root@cid# cd /mydata

root@cid# ls

root@cid# exit

 

step6:

For share volume (/mydata) with new container con3

#docker  run  -it   –name  con3 –privileged=true    –volumes-from   con2    ubuntu   /bin/bash

root@cid# ls

root@cid# cd    /mydata

root@cid# ls

root@cid# touch   con3{a..e}.txt

root@cid# ls

root@cid# exit

 

Step7:

Start container con1 to verify con3 created data available or not

#docker   ps   -a

#docker   start   con1

#docker    attach  con1

root@cid# ls

root@cid# cd /mydata

root@cid# ls

root@cid# exit

 

Map Volume Host OS to container

Step1:

Create directory for volume

#mkdir  pune

#pwd

#/root/pune

 

Step2:

Map pune volume with container

#docker   run   -it   –name   mycon1   -v  /root/pune:/mypune   –privileged=true    ubuntu    /bin/bash

root@cid# ls

root@cid# cd  /mypune

root@cid#  touch  mycon1{a..e}.txt

root@cid#  ls

root@cid#  exit

 

step3:

check hosts os directory pune

#cd   /root/pune

#ls

 all content available create in container

 

step4:

create content in host os 

#cd  /root/pune

#ls

#touch hostos{1..5}.txt

#ls

Step5:

Check content inside the container

#docker   start   mycon1

#docker    attach    mycon1

root@cid#  cd    /mypune

root@cid#  ls

root@cid#  exit

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Web hosting in container

docker run -dt –name webcon -p 80:80 ubuntu

#docker ps

#docker stop icon1

#docker ps

#docker exec -it webcon /bin/bash

#docker port webcon

#docker exec -it webcon /bin/bash

Author:-

Abhijit Dahatonde

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