How to build and configure automatically custom Docker image using dockerfile on CentOS and RHEL 6/7 step by step guide

Build docker image from dockerfile | In this article we will learn how to build and configure automatically custom docker image using dockerfile on centos and rhel 7 system. Now we need to know the definition of dockerfile.

What is Dockerfile?

Dockerfile is a set of instruction which will be run to deploy an application.Docker image is created based on the instruction of docker file.

How to create a Dockerfile to build a docker image

First we need to create dockerfile which is filled by a set of instruction as below.

#touch dockerfile

Then edit the dockerfile and add the below lines.

FROM centos

MAINTAINER abc@email.com

RUN yum update

RUN yum install –y httpd

CMD "<your message>”

From the above line indicates that:

FROM : from which base image docker image will be created.

MAINTAINER: who is maintain the dockerfile.

RUN: run defined set of instruction which use to un the command and create the docker image.

CMD: message for the user.

Build docker image from dockerfile

To build  docker image from  dockerfile we need to execute the below command.

#docker build  -t centos-apache:v1 <dockefile location>

Sending build context to Docker daemon  3.072kB

Step 1/3 : FROM centos

latest: Pulling from library/centos

a02a4930cb5d: Pull complete

Digest: sha256:184e5f35598e333bfa7de10d8fb1cebb5ee4df5bc0f970bf2b1e7c7345136426

Status: Downloaded newer image for centos:latest

 ---> 1e1148e4cc2c

Step 2/3 : MAINTAINER abc@email.com

 ---> Running in 0ab288df423f

Removing intermediate container 0ab288df423f

 ---> a6f733efac95

Step 3/3 : RUN yum install -y  httpd

 ---> Running in 51fd64d94a5e

Loaded plugins: fastestmirror, ovl

Determining fastest mirrors

Installed:

  httpd.x86_64 0:2.4.6-88.el7.centos

Complete!

Removing intermediate container 51fd64d94a5e

 ---> 835398195c98

Successfully built 835398195c98

Successfully tagged centos-apache:v1

Build docker image from dockerfile

From the above command indicates that:

-t: mentin the tag to the image

Centos-apache: centos-apache is the image name .

V1: v1 is the tag of the image.

<dockerfile location>: location of the docker file.

After executing the above command we verify the images using the below command.

#docker images

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE

centos-apache       v1                  835398195c98        2 minutes ago       305MB

That’s all. If this article is helpful  to know about Dockerfile and Build docker image from docker file please share it!!!!

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