This article demonstrates how to get a web site running using Docker. We’re starting with a Linux server (doesn’t matter which distribution). We’re going to pull down an Docker image from the public repository, modify it’s “index” file, and expose it – making it publicly accessible. I’ve added a little FAQ at the end of this artile.
To make it interesting, we’re going to run a php “index” file: “index.php”.
Let’s start by installing Docker:
Ubuntu:
https://docs.docker.com/engine/install/ubuntu/
CentOS:
https://docs.docker.com/engine/install/centos/
Now we can pull down an image from the public repository. This image is basically a template for us to manipulate for our own needs. It will run just fine without any modifications, but the site will be the stock-standard “apache” page. But because we want our own “index.php” to execute, we’re going to modify it.
docker pull php:8.0-apache
Let’s see our images. So far there should be just one:
docker images
The output:
REPOSITORY TAG IMAGE ID CREATED SIZE docker.io/php 8.0-apache 475b1a998b6f 5 days ago 455 MB
Create a directory and create a file in it called “Dockerfile”:
mkdir ~/docker cd ~/docker vi Dockerfile
Put the following into the “Dockerfile”:
FROM php:8.0-apache COPY ./index.php /var/www/html/ EXPOSE 80
Now create your “index.php” file in the same location as the “Dockerfile”. You can see from the above Dockerfile contents that we’re referring to it. Here’s my example “index.php” file:
<?php echo "This is a php script!"; ?>
Now we’re ready to build our new Docker image. Once built, we can run it. Tip: If we didn’t “poll” the image in the earlier step, Docker would automatically pull it down as a result of the following “build” command.
# I'm calling my image "my-web-server" but you can call it whatever you like... docker build . -t my-web-server
Let’s see our list of images now:
docker images
The output:
REPOSITORY TAG IMAGE ID CREATED SIZE my-web-server latest 6798fce89abd 32 seconds ago 455 MB docker.io/php 8.0-apache 475b1a998b6f 5 days ago 455 MB
Now run it. This turns our image into a container. A container can be stopped and restarted. All containers come from an image. The ‘-d’ puts it into the background. The ‘-p’ allow us to specify a port to expose it on – the port that we’ll visit.
docker run -d -p 5000:80 my-web-server
Confirm it’s running:
docker container ls
The output:
docker container ls CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 7600e6e385cd my-web-server "docker-php-entryp..." 4 seconds ago Up 3 seconds 0.0.0.0:5000->80/tcp mystifying_wing
Test it. Visit that exposed port “5000”. Of course, we could expose it on any other port including “80”.
curl http://localhost:5000
Let’s stop our container:
# Where "7600e6e385cd" is the name of our container - from the "docker container ls" command above... docker stop 7600e6e385cd
We can start it again:
docker start 7600e6e385cd
We can remove/delete the container:
docker stop 7600e6e385cd docker container rm 7600e6e385cd
We can remove/delete the original image and the image we created from the original image. Start by listing the images
docker images
The output:
REPOSITORY TAG IMAGE ID CREATED SIZE my-web-server latest 92e2324e62da 4 minutes ago 455 MB docker.io/php 8.0-apache 475b1a998b6f 5 days ago 455 MB
Now we delete them:
docker images rm 92e2324e62da 475b1a998b6f
And we’re done.
FAQ:
Q. Can I log into a Docker container while it’s running?
A. Yes, you use use the command “docker exec -it 7600e6e385cd /bin/bash” (where “7600e6e385cd” is the container ID) and you will be given the prompt for that container.
Q. If I log into a Docker container and make changes, will those changes persist?
A. Any changes will persist between “docker stop” and “docker start” commands, but they will not persist after a “docker run” command. Start and stop operations are safe. But Run operations create a new container with a new ID leaving all previous/other containers untouched.
Q. Does “docker run” destroy previously started containers originating form the same image?
A. No, running “docker run” creates a new and unique container with a unique ID.
