Docker Intro

Go to hub.docker.com
search for ubuntu, centos, mysql

How to create custom image

Custom file --> is your --> own image

Dickerfile -> Docker scripting language

Traditionally  just to use a web server, we used to use physical machine, physical network, but these days we have a host a machine, we have a VM, and inside VM, we can run docker.



1. Install Redhat 8 on your system.

# docker ps
# docker ps -a

# yum install python36
# python3


# cat Dockerfile
FROM centos

RUN yum install python36 -y

# docker images
# docker images | grep exp

# docker build -t expanor:v1 /ws/

Now, your image is ready. Based on this image, you can launch 100s of other os instances

# docker run -it ==nme os2 nexpanor:v1
# docker ps
# python3

# vi Dockerfile
FROM centos
RUN yum install python36 -y


# docker rm -f $(docker ps -a -9)   # terminates all docker instalnces

# docker run -it --name os1 centos

Create a file on your VM
# yum install https -y
# vi index.html
Life is beautiful !!!
# docker run -it --name OS1 centos  # Create an OS docker instance OS1
# docker cp index.html os1:/var/www/html

On your docker instance, try to start the webserver
You will get error

Now, go ahead and start wen server on your VM.
# systemctl start httpd
# systemctl status htpd

look at the httpd service file at /usr/lib/systemd/system/httpd.service

Now, cat that file and look under

execStart
ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND

now remove $OPTIONS and manually run the command below on docker

# /usr/sbin/httpd -DFOREGROUND

To find the IP address of docker, you can use inspect option
# docker inspect OS1

# docker rm -r os1

Review
#  mkdir /workfile; cd /workfile
# cat >>index.html
Welcome to my page !!!

# cat Dockerfile
FROM centos

RUN yum install httpd -y


# docker images
# docker build -t expanor:v1 /ws/

Now, your image is ready. Based on this image, you can create hundreds of other docker instances.

# docker imags  | grep exp  - to see your image you just created.

# docker ps
# docker run -it --name os2 expanor:v1
# docker ps

# cat Dockerfile
FROM centos

RUN yum install httpd -y

RUN yum install python36 -y
CMD python3

# docker build -it expanor:v2 /ws/

when you run above command, you will be at python prompt. just type exot() to close the doccer sesssion.

# docker ps
# docker rm -f $(docker ps = a =9)  # terminate att docker session

# docker run -it --name OS1 centos