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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How to deploy and run application inside the isolated docker container on CentOS and RHEL 6/7 step by step guide

Deploy and Docker run image and save new image using Docker commit|In the previous article we learned  how to install Docker on centos and redhat linux system and learned use of docker container on centos and redhat linux system. In this article we will learn how to deploy and run an application inside the docker container.

Deploy and run an application inside Docker container

In the previous article we have installed centos docker image and here we will learn Docker run image (centos based docker container) where apache service will be installed . To do this we need to execute the below command.

[root@localhost ~]# docker run centos bash -c "yum install -y httpd"

--> Finished Dependency Resolution

Dependencies Resolved

================================================================================

Package             Arch          Version                    Repository   Size

================================================================================

Installing:

httpd               x86_64        2.4.6-88.el7.centos        base        2.7 M

Installing for dependencies:

apr                 x86_64        1.4.8-3.el7_4.1            base        103 k

apr-util            x86_64        1.5.2-6.el7                base         92 k

centos-logos        noarch        70.0.6-3.el7.centos        base         21 M

httpd-tools         x86_64        2.4.6-88.el7.centos        base         90 k

mailcap             noarch        2.1.41-2.el7               base         31 k

Transaction Summary

================================================================================

Install  1 Package (+5 Dependent packages)

Total download size: 24 M

How to deploy and run application inside the isolated docker container on CentOS and RHEL 6/7 step by step guide

After that we need to execute the below command to know the container id.

#docker ps  -a

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS     PORTS               NAMES

8b451071cdd1        centos              "bash -c 'yum instal…"   3 minutes ago       Exited (0) 2 minutes ago                       agitated_hawking

Using this id we can stop , start and attach the container.

Docker Commit

We can save the new image using the container id . To save the new image we can execute the below command.To save the new image from container ID we use "Docker Commit" command.

#Docker commit <container ID> <New image neme>

# docker commit 8b451071cdd1 centos-apache

sha256:2f81cfc333d7cf8d61d3fbf21366ee1dd21f57c94bb5d7ca859ae4e99b9104c0

We can verify the new image name using the below command.

# docker images

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE

centos-apache       latest              2f81cfc333d7        33 seconds ago      305MB

Map the host container port on docker

To map the host container port we can run the below command.

 # docker run -it -p 81:80  centos-apache /bin/bash

[root@276c18a6318d /]#

After that we press ctrl+p and ctrl+q to continue the process and type the curl command on the shell to get the apache page as below.

Note: 81 is the host port and 80 is the container port.

#curl http://localhost

That’s all. If this article is helpful to know about Docker run image and save new image using Docker commit please share it!

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How to download and remove Docker Image and use Docker container on CentOS and RHEL 6/7 and Ubuntu 16.04 step by step guide

Download Docker Image from the Docker Hub and Docker Remove Image | In this article we will learn how to download docker image and after downloading the image start and run docker container and play with docker container to run and deploy an application and how to remove docker image.

How to download Docker Image

We can download Docker Image from the Docker Hub on your linux system using the below command. Suppose we are going to download centos image first we need to search the available images into the central docker repo using the below command.

[root@localhost ~]# docker search centos

How to download Docker Image and use Docker container on CentOS and RHEL 6/7 step by step guide

Once getting the available images we can download the image using the below command.

[root@localhost ~]# docker pull centos

latest: Pulling from centos

e4b082fc6cdb: Pull complete

f016d310caa9: Pull complete

ab9a80ab07d0: Pull complete

Digest: sha256:38777a4106f0072649128ea4236241345a3ed21c55abbbd53bad5342549f6126

Status: Downloaded newer image for centos:latest

To list the available docker images we can execute the below command.

 [root@localhost ~]# docker images

REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE

centos              latest              ab9a80ab07d0        6 weeks ago         201.8 MB

Docker Remove Image

If you want to remove docker image you can execute the below command.

[root@localhost ~]# docker rmi centos

If you want to remove docker image force fully then you need to use the below command.

[root@localhost ~]# docker rmi -f ab9a80ab07d0

How To Use Docker Container

 After downloaded the image we can start and run the docker container.  We can run the container using the below command. In this below command run the container using the downloaded image and get the downloaded centos release version.

[root@localhost ~]# docker run centos cat /etc/centos-release

CentOS Linux release 7.6.1810 (Core)

After running the docker container we need to know container id which is very useful to start and stop the container as well as you can use container name also to start and stop the container.

[root@localhost ~]# docker ps -a

CONTAINER ID        IMAGE               COMMAND                CREATED              STATUS                          PORTS               NAMES

a4d4d2937780        centos              "cat /etc/centos-rel   About a minute ago   Exited (0) About a minute ago                       sick_yalow

And you can start the container again using the below command.

[root@localhost ~]# docker start <container ID>

How To Run interactive session for docker container

To run interactive session for a docker container we can use the below command.

[root@localhost ~]# docker run –it centos bash

If you type exit into the shell the container will be stop and if you don’t want to stop container process you can press ctrl+p and ctrl+q at a time.

You can attach the container using the below command

[root@localhost ~]# docker attach <container id>

You can check the container process using the below command.

[root@localhost ~]# docker ps

That’s all.If this article is helpful to know about Download Docker Image from the Docker Hub and Docker Remove Image please share it!

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How to install Docker on CentOS 7 /RHEL 7/Ubuntu 16.04 step by step guide

Install Docker in Ubuntu 16.04 / 18.04 LTS /CentOS 7/ RHEL 7 |In this tutorial we learn what is docker and how to install Docker on CentOS 7,RHEL 7 and Ubuntu 16.04 / 18.04.

What is Docker?

Docker is container service management. Docker is open source lightweight tool which allow us to create ,ship and run an application on isolated container. Developing task became easy for developer for docker because they only focus on coding.   

Docker Engine is important component for docker which is building the images and creating the container.

How to install Docker on CentOS 7 /RHEL 7

Docker package is available in the centos extra repository. you can install Docker package using the below command.

[root@localhost ~]# yum install docker -y

Install Docker in Ubuntu16.04/18.04

Docker package is available in ubuntu by default. To install Docker In Ubuntu 16.04 / 18.04 LTS we need to execute below command .There is no need to install extra repository like centos and redhat and oracle also.

# apt-get install docker -y

After installed the Docker package we need to start the docker service and enable the service at startup mode execute the below command.

 [root@localhost ~]#systemctl start docker

[root@localhost ~]#systemctl enable docker

After doing the above steps we can check the docker service status using the below command.

[root@localhost ~]#systemctl status docker

● docker.service - Docker Application Container Engine

   Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled)

   Active: active (running) since Thu 2019-01-17 22:18:43 IST; 12s ago

     Docs: http://docs.docker.com

 Main PID: 2324 (dockerd-current)

   CGroup: /system.slice/docker.service

           ├─2324 /usr/bin/dockerd-current --add-runtime docker-runc=/usr/lib...

           └─2328 /usr/bin/docker-containerd-current -l unix:///var/run/docke...

To know the Docker version and info

To know the docker version and docker info we need to execute the below command.

[root@localhost ~]#docker version

How to install Docker on CentOS 7 /RHEL 7/Ubuntu 16.04

And get the docker info run the below command.

[root@localhost ~]#docker info

Containers: 0

 Running: 0

 Paused: 0

 Stopped: 0

Images: 0

Server Version: 1.13.1

Storage Driver: overlay2

 Backing Filesystem: xfs

 Supports d_type: true

 Native Overlay Diff: true

Logging Driver: journald

Cgroup Driver: systemd

Plugins:

 Volume: local

 Network: bridge host macvlan null overlay

Swarm: inactive

Runtimes: docker-runc runc

Default Runtime: docker-runc

Init Binary: /usr/libexec/docker/docker-init-current

Verify Docker working or not on CentOS 7 and RHEL 7 and Ubuntu 16.04 /18.04

To verify Docker is working or not we can run test container image using the below command  and if you will get this below message then docker works correctly on your system.

[root@localhost ~]# docker run hello-world

Hello from Docker!

This message shows that your installation appears to be working correctly.

To get full list of docker command we can execute the command on the terminal.

[root@localhost ~]# docker

That’s all.If this article is helpful to know about Install Docker in Ubuntu16.04 / 18.04 ,CentOS 7/ RHEL7 please share it!!!

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