How to Create a Docker Image for an Application

Docker images are an essential part of the Docker platform. A docker image is an instructions file used to create and manage containers in Docker. The developer must require the Docker image to containerize the application. The image file includes instructions that guide and help the Docker container to execute the program.

This article will illustrate the method for creating an image for an application.

How to Create an Image for an Application?

Images are the core of the Docker platform. To containerize the application, users are required to create the Docker image.

Check out the mentioned instructions to build the image in Docker for an application.

Step 1: Open Terminal

Firstly, launch the terminal to run Docker commands. For instance, we have utilized the “git bash” terminal. However, users can use Windows default terminal as well:

Step 2: Open the Project Directory

Next, navigate to the project directory through the “cd <directory-path>” command:

$ cd "C:\Multistage"

Step 3: Create and Open Program File

Create a program file to specify the program. For this purpose, users can use Windows Notepad. For instance, we have utilized the “nano” text editor:

$ nano main.go

Paste the below-coded instructions into the file and press the “CTRL+O” to save the change for a nano text editor. For Notepad, press “CTRL+S” to save changes:

Package main

import (

"fmt"

"log"

"net/http"

)

func handler (w http.ResponseWriter, r *http.Request) {

fmt.Fprintf(w, "Hello! Welcome to LinuxHint Tutorial")

}

func main () {

http.HandleFunc("/", handler)

log.Fatal(http.ListenAndServe("0.0.0.0:8080", nil))

}

Step 4: Create DockerFile

In the next step, create a Dockerfile. Remember that the file’s name must be “Dockerfile” without any extension:

$ nano Dockerfile

Paste the below-mentioned instructions into the “Dockerfile”. These instructions will be used to create a Docker image:

FROM golang:1.8

WORKDIR /go/src/app

COPY main.go .

RUN go build -o webserver .

CMD ["./webserver"]

Step 5: Create Docker Image

Now, create a fresh Docker image with the help of the below-mentioned command:

$ docker build -t new-web-image .

In the above command, the “-t” option specifies the tag or image name:

Step 6: Run Docker Image

Now, run the Docker image to create and execute the Docker container to deploy the application within the container:

$ docker run -p 8080:8080 new-web-image

Here, the “-p” option is used to specify the exposed port on which the container will execute and deploy the project:

For confirmation, go to the “localhost:8080” URL on the browser:

From the above output, you can see that we have successfully created and run the image to execute the application in the container.

Conclusion

To build an image in Docker for an application, first, make a new Dockerfile that contains essential instructions to create a new image. After that, utilize the “docker build -t <image-name> .” command to make a new Docker image for the application. This post has illustrated the procedure for creating an image for an application in Docker.