Introduction:
In the previous article , we saw how to install docker, in this chapter we’ll go through building our own docker image and publish it to the docker hub.
Lets Get Started:
To build a docker image, we need to have all the code, libraries and its dependencies to be available.
This is a demonstration of a simple web application which has only a static webpage and is being served by a HTTP web server. We are going using lighttpd (can be Apache or Nginx).
You can find all the code on the GitHub repository.
Clone the repository and CD into it. fbweb directory contains all our code. Ignore the yml files for now. They are for Kubernetes.
& git clone https://github.com/sagarkrp/fakeweb.git
& cd fakeweb
We use Dockerfile to write all the instruction needed to build our Image.
Lets understand one by one.
FROM: Use an existing Image as a base Image.
RUN: To run any commands for example “apt update, mvn clean install, npm install, python -r requirement.txt , dnf install httpd” etc.
COPY: Copies our application code to the OS inside the Image.
ENTRYPOINT/CMD : Command to start our application.
FROM ubuntu:22.10 - We are using Ubuntu as base image.
RUN apt update -y - Updating repository index as we generally do in Linux.
RUN apt install lighttpd -y - Installing lighttpd webserver.
COPY fbweb/ /var/www/html/ - Copying our application to the web server root directory.
ENTRYPOINT service lighttpd start && /bin/bash - Starting the web server.
To build the image, we need to run the docker build command: docker build -t name:tag .
docker build -t fbweb:1.0 .
After Entering this command , we shall see a updates like these:
If there are no errors, this will will be completed with this kind of message:
To view the list of Images we can use : docker images command.
└──| docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
fbweb 1.0 bcb23d33bf82 1 minute ago 163MB
Now lets run this image with the following command:
──| docker run --name fb -td -p 80:80 fbweb:1.0
551eddaa8434ac7665e85bf7e959493eb21783ad4f332fdcc5b678e5769ae233
──| docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
551eddaa8434 fbweb:1.0 "/bin/sh -c 'service…" 6 seconds ago Up 6 seconds 0.0.0.0:80->80/tcp, :::80->80/tcp fb
- -p:
: = Publish, runs the app on the host port of 80. Even though we have not explicitly exposed our app , by default a web server runs on port 80. - -d : Runs in detached mode, meaning in the background and leaves the terminal to use.
- — name: To assign a custom name to the container. If we don’t mention anything, docker will auto assign a name.
The docker ps command shows the currently active containers. If you don’t see your container , use -a to find out what happened. You may see the status as “Exited” as opposed to “ Up 6 secs ago” as seen above.
If your container is in exited state , use docker logs against the container id or name to find out the reason why it exited.
docker ps :- shows active containers
docker ps -a :-shows both active and stopped containers
docker logs <container_id> :- find out why container exited
Now lets browse the IP or URL.
ta-da! Our application is running fine. We successfully containerized the application.
Push the Image to docker hub:
Tag the image with repository name using below command. After tagging we should see another image appear in the list with same ID.
──| docker tag fbweb:1.0 sagarkp/fbweb:1.0
└──| docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
fbweb 1.0 9443bff58bb3 About an hour ago 163MB
sagarkp/fbweb 1.0 9443bff58bb3 About an hour ago 163MB
Now to push to docker hub, we first need to provide docker hub credentials in our terminal. Use the below command and enter the creds when asked.
docker login
Once we are logged in, we can use the docker push command to push the image.
──| docker push sagarkp/fbweb:1.0
The push refers to repository [docker.io/sagarkp/fbweb]
a2517707f654: Pushed
5cd1ef7c3719: Pushing [=============================> ] 32.96MB/56.14MB
61800684fb13: Pushing [=================> ] 12.47MB/36.45MB
c8211604066d: Pushing [================> ] 22.9MB/70.25MB
Now if we login to Docker Hub in our browser, we can see the image and it was published a few seconds ago.
Whalesome!!. We have successfully built and pushed our image to docker hub.