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Docker

Docker is  an operating-system-level virtualization makes it easier to create and deploy applications in an isolated environment. A Dockerfile is a script that contains collections of commands and instructions that will be automatically executed in sequence in the docker environment for building a new docker image.

All sysadmin or developer  need a  specific configuration for a proyect version, dependecies users , for old school the solution is virtual machine  the principal difference  whit Docker is more lightweight

Prerequisites

I use Debian GNU Linux stretch for docker base image

root privileges

 

Below are some dockerfile commands you must know:

FROM The base image for building a new image. This command must be on top of the dockerfile.

MAINTAINER Optional, it contains the name of the maintainer of the image.

RUN Used to execute a command during the build process of the docker image.

ADD Copy a file from the host machine to the new docker image. There is an option to use an URL for the file, docker will then download that file to the destination directory.

ENV Define an environment variable.

CMD Used for executing commands when we build a new container from the docker image.

ENTRYPOINT Define the default command that will be executed when the container is running.

WORKDIR This is directive for CMD command to be executed.

USER Set the user or UID for the container created with the image.

VOLUME Enable access/linked directory between the container and the host machine.

 

Now let’s stat to create our first dockerfile.

Step 1

apt-get install docker

 

Create  Dockerfile, default start.sh and supervisord.conf

 

Step 3 – Build New Docker Image and Create New Container Based on it

The Dockerfile and all required config files have been created, now we can build a new docker image based on Ubuntu 16.04 and our dockerfile with the docker command below:

docker build -t nginx_image .

When the command completed successfully, we can check the new image ‘nginx_image’ with the docker command below:

docker images

Then we can try to create a new container based on nginx_images. And before create new container, we can create new directory on the host machine for the webroot data.

mkdir -p /webroot

Now run the new container with command below:

docker run -d -v /webroot:/var/www/html -p 80:80 --name hakase nginx_image

Then we can check that the new container with name hakase based on ‘nginx_image’ is running:

docker ps

Check if our Docker container is running

Note:

  • –name hakase nginx_image = We create a new container with the name ‘hakase’, based on docker image ‘nginx_images’.
  • -p 80:80 = hakase container running on port 80 on the host machine.
  • -v /webroot:/var/www/html = /webroot directory on the host machine rewrite the /var/www/html directory on the container.

The new container based on the nginx_image is running without error.

Step 4 – Testing Nginx and PHP-FPM in the Container

Try to create a new index.html file in the /webroot directory with echo:

echo '<h1>Nginx and PHP-FPM 7 inside Docker Container</h1>' > /webroot/index.html

Testing with curl command by accessing the host machine ip address.

curl 192.168.1.250
curl -I 192.168.1.250

We will see results below.

 

Next, test that PHP-FPM 7.0 is running by creating a new phpinfo file in the /webroot directory on the host machine.

echo '<?php phpinfo(); ?>' > /webroot/info.php

Open the web browser and type the host machine IP address:

http://192.168.1.248/info.php

Now you can see the output of the phpinfo file.

PHP-FPM is working nicely

the new docker image ‘nginx_image’ has been successfully created, now we can create more containers based on that image.

 

credits:https://www.howtoforge.com/tutorial/how-to-create-docker-images-with-dockerfile/

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