Docker Image
- We need to package the applications developed in our organization as docker images
- Advantages of docker images:
- Running an app on docker will give more priority to cpu and other resources consumed by application rather than os
- Cost Reduction: On one host we can run multiple applications seamlessly which reduces hardware costs and os costs
- Docker is extremely portable, Docker container literally runs anywhere
Installing Docker
- Lets install Docker on a linux machine
- We can create a linux vm on any cloud
- aws Refer Here
- azure Refer Here
- gcp
- Lets create a ubuntu instance in your cloud
- For installing docker we will be using the shell script approach which installs the latest version on linux Refer Here
- Login into the vm
sudo apt update
curl -fsSL https://get.docker.com -o get-docker.sh
sh get-docker.sh
- Exit and relogin and execute the command docker info
First look at building docker images
- Lets take the lampstack as an example Refer Here
- First step is to make a note of all the steps required to install/configure your application manually on linux/windows machine
- Then try to create a Dockerfile which consists of instructions to install/configure your application
- Dockerfile is a text file which consists of set of Instructions to build a docker image
- Lets try to make a note of steps to manually create a lamp server on ubuntu server
sudo apt update
sudo apt install apache2 -y
sudo apt install php libapache2-mod-php php-mysql php-cli -y
echo '<?php phpinfo(); ?>' | sudo tee /var/www/html/info.php
- Basic docker image creation process is
- choose a base image
- add your installation/configuration steps
- create the new image
- To choose a base image navigate to Refer Here
- In docker the version of image is referred as tag Refer Here
- Since our steps are based on ubuntu 18.04 lets choose the tag
- Lets try to manually check if the image will work or not
- So lets try to create a container with the ubuntu image and 18.04 tag
docker container run -it <image> /bin/bash
- In docker convention is
<image-name>:<tag>=>ubuntu:18.04
docker container run -it ubuntu:18.04 /bin/bash
- This command creates a ubuntu 18 container and you will be logged in to the container as a root user
- For commands start using cheatsheet Refer Here
- In the container we have executed the following steps
apt update
apt install apache2 -y
apt install php libapache2-mod-php php-mysql php-cli -y
echo '<?php phpinfo(); ?>' | tee /var/www/html/info.php
service apache2 start
- The way to write Dockerfile contents
FROM ubuntu:18.04
RUN apt update
RUN apt install apache2 -y
RUN apt install php libapache2-mod-php php-mysql php-cli -y
RUN echo '<?php phpinfo(); ?>' | tee /var/www/html/info.php
RUN service apache2 start
EXPOSE 80
- Lets look at some Dockerfiles created by community
- ubuntu Refer Here
- tomcat Refer Here
