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Chapter 2. Get Started with Containers

2.1. Install and Deploy an Apache Web Server Container

2.1.1. Overview

A Web server is one of the most basic examples used to illustrate how containers work. The procedure in this topic does the following:

  • Builds an Apache (httpd) Web server inside a container
  • Exposes the service on port 80 of the host
  • Serves a simple index.html file
  • Displays data from a backend server (needs additional MariaDB container described later)

2.1.2. Creating and running the Apache Web Server Container

  1. Install system: Install a RHEL 7 or RHEL Atomic system that includes the docker package and start the docker service.

  2. Pull image: Pull the rhel7 image by typing the following: 

    # docker pull rhel7:latest

  3. Get tarball with supporting files: Download the tarball file attached to this article (get it here: web_cont_3.tgz), download it to a new mywebcontainer directory, and untar it as follows: 

    # mkdir ~/mywebcontainer
# cp web_cont*.tgz ~/mywebcontainer
# cd ~/mywebcontainer
# tar xvf web_cont*.tgz
action
Dockerfile

  4. Modify action CGI script: Edit the action file as needed, which will be used to get data from the backend database server container. This script assumes that the docker0 interface on the host system is at IP address 172.17.42.1, you can login to the database with the dbuser1 user account and redhat as the password, and use the database named gss. If that is the IP address and you use the database container described later, you don’t need to modify this script. (You can also just ignore this script and just use the Web server to get HTML content.) 

    #!/usr/bin/python
# -*- coding: utf-8 -*-
import MySQLdb as mdb
import os

con = mdb.connect(os.getenv('DB_SERVICE_SERVICE_HOST','172.17.42.1'), 'dbuser1', 'redhat', 'gss')

with con:

    cur = con.cursor()
    cur.execute("SELECT MESSAGE FROM atomic_training")

    rows = cur.fetchall()

    print 'Content-type:text/html\r\n\r\n'
    print '<html>'
    print '<head>'
    print '<title>My Application</title>'
    print '</head>'
    print '<body>'

    for row in rows:
        print '<h2>' + row[0] + '</h2>'

    print '</body>'
    print '</html>'

    con.close()

  5. Check the Dockerfile: Modify the Dockerfile file in the ~/mywebcontainer directory as needed (perhaps only modify Maintainer_Name to add your name). Here are the contents of that file: 

    # Webserver container with CGI python script
# Using RHEL 7 base image and Apache Web server
# Version 1

# Pull the rhel image from the local registry
FROM rhel7:latest
USER root

MAINTAINER Maintainer_Name

# Fix per https://bugzilla.redhat.com/show_bug.cgi?id=1192200
RUN yum -y install deltarpm yum-utils --disablerepo=*-eus-* --disablerepo=*-htb-* *-sjis-*\
    --disablerepo=*-ha-* --disablerepo=*-rt-* --disablerepo=*-lb-* --disablerepo=*-rs-* --disablerepo=*-sap-*

RUN yum-config-manager --disable *-eus-* *-htb-* *-ha-* *-rt-* *-lb-* *-rs-* *-sap-* *-sjis* > /dev/null

# Update image
RUN yum update -y
RUN yum install httpd procps-ng MySQL-python -y

# Add configuration file
ADD action /var/www/cgi-bin/action
RUN echo "PassEnv DB_SERVICE_SERVICE_HOST" >> /etc/httpd/conf/httpd.conf
RUN chown root:apache /var/www/cgi-bin/action
RUN chmod 755 /var/www/cgi-bin/action
RUN echo "The Web Server is Running" > /var/www/html/index.html
EXPOSE 80

# Start the service
CMD mkdir /run/httpd ; /usr/sbin/httpd -D FOREGROUND

  6. Build Web server container: From the directory containing the Dockerfile file and other content, type the following: 

    # docker build -t webwithdb .
Sending build context to Docker daemon 4.096 kB
Sending build context to Docker daemon
Step 0 : FROM rhel7:latest
 ---> bef54b8f8a2f
Step 1 : USER root
 ---> Running in 00c28d347131
 ---> cd7ef0fcaf55
...

  7. Start the Web server container: To start the container image, run the following command: 

    # docker run -d -p 80:80 --name=mywebwithdb webwithdb

  8. Test the Web server container: To check that the Web server is operational, run the first curl command below. If you have the backend database container running, try the second command: 

    # curl http://localhost/index.html
The Web Server is Running
# curl http://localhost/cgi-bin/action
<html>
<head>
<title>My Application</title>
</head>
<body>
<h2>RedHat rocks</h2>
<h2>Success</h2>
</body>
</html>
</tt></pre>

    If you have a Web browser installed on the localhost, you can open a Web browser to see as better representation of the few lines of output. Just open the browser to this URL: http://localhost/cgi-bin/action

2.1.3. Tips for this container

Here are some tips to help you use the Web Server container:

  • Modify for MariaDB: To use this container with the MariaDB container (described later), you may need to edit the action script and change the IP address from 172.17.42.1 to the host IP on the docker0 interface. To find what that address is on your host, type the following: 
# ip a | grep docker0 | grep inet
    inet 172.17.42.1/16 scope global docker0
  • Adding content: You can include your own content, mounted from the local host, by using the -v option on the docker run command line. For example: 
# docker run -d -p 80:80 -v /var/www/html:/var/www/html \
     --name=mywebwithdb webwithdb

2.1.4. Attachments

2.2. Install and Deploy a MariaDB Container

2.2.1. Overview

Using MariaDB, you can set up a basic database in a container that can be accessed by other applications. The procedure in this topic does the following:

  • Builds a MariaDB database server inside a docker formatted container
  • Exposes the service on port 3306 of the host
  • Starts up the database service to share a few pieces of information
  • Allows a script from Web server to query the database (needs additional Web server container described later)
  • Offers tips on how to use and extend this container

2.2.2. Creating and running the MariaDB Database Server Container

  1. Install system: Install a Red Hat Enterprise Linux 7 or Red Hat Enterprise Linux Atomic Host system that includes the docker package and start the docker service.

  2. Pull image: Pull the rhel7 image by typing the following: 

    # docker pull rhel7:latest

  3. Get tarball with supporting files: Download the tarball file attached to this article (mariadb_cont_2.tgz), download it to a new mydbcontainer directory, and untar it as follows: 

    # mkdir ~/mydbcontainer
# cp mariadb_cont*.tgz ~/mydbcontainer
# cd ~/mydbcontainer
# tar xvf mariadb_cont*.tgz
gss_db.sql
Dockerfile

  4. Check the Dockerfile: Modify the Dockerfile file in the ~/mydbcontainer directory as needed (perhaps only modify Maintainer_Name to add your name). Here are the contents of that file: 

    # Database container with simple data for a Web application
# Using RHEL 7 base image and MariahDB database
# Version 1

# Pull the rhel image from the local repository
FROM rhel7:latest
USER root

MAINTAINER Maintainer_Name

# Update image
RUN yum update -y --disablerepo=*-eus-* --disablerepo=*-htb-* --disablerepo=*sjis* \
    --disablerepo=*-ha-* --disablerepo=*-rt-* --disablerepo=*-lb-* \
    --disablerepo=*-rs-* --disablerepo=*-sap-*

RUN yum-config-manager --disable *-eus-* *-htb-* *-ha-* *-rt-* *-lb-* \
    *-rs-* *-sap-* *-sjis-* > /dev/null

# Add Mariahdb software
RUN yum -y install net-tools mariadb-server

# Set up Mariahdb database
ADD gss_db.sql /tmp/gss_db.sql
RUN /usr/libexec/mariadb-prepare-db-dir
RUN test -d /var/run/mariadb || mkdir /var/run/mariadb; \
    chmod 0777 /var/run/mariadb; \
    /usr/bin/mysqld_safe --basedir=/usr & \
    sleep 10s && \
    /usr/bin/mysqladmin -u root password 'redhat' && \
    mysql --user=root --password=redhat < /tmp/gss_db.sql && \
    mysqladmin shutdown --password=redhat

# Expose Mysql port 3306
EXPOSE 3306

# Start the service
CMD test -d /var/run/mariadb || mkdir /var/run/mariadb; chmod 0777 /var/run/mariadb;/usr/bin/mysqld_safe --basedir=/usr

  5. Build database server container: From the directory containing the Dockerfile file and other content, type the following: 

    # docker build -t dbforweb .
Sending build context to Docker daemon 528.4 kB
Sending build context to Docker daemon
Step 0 : FROM rhel7:latest
 ---> bef54b8f8a2f
Step 1 : USER root
...

  6. Start the database server container: To start the container image, run the following command: 

    # docker run -d -p 3306:3306 --name=mydbforweb dbforweb

  7. Test the database server container: Assuming the docker0 interface on the host is 172.17.42.1 (yours may be different), check that the database container is operational by running the nc command (in RHEL 7, type yum install nc to get it) as shown here: 

    # nc -v 172.17.42.1 3306
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connected to 172.17.42.1:3306.
R
5.5.44-MariaDB?acL3YF31?X?FWbiiTIO2Kd6mysql_native_password Ctrl-C

2.2.3. Tips for this container

Here are some tips to help you use the Web Server container:

  • Adding your own database: You can include your own MariaDB content by copying your database file to the build directory and changing the name of the database file from gss_db.sql to the name of your database (in several places in the Dockerfile file).
  • Orchestrate containers: A better way to manage this container with other containers is to use Kubernetes to orchestrate them into pods.

2.2.4. Attachments