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Creating Prebundled Machine Images for the Cloud
by Kiran C. Nair
Learn how to create a custom virtual machine image prebundled with Oracle WebLogic Server 11g and Oracle Database XE, as well as the basics of creating init scripts and configuring services to run at user-defined runlevels
Published November 2009
Downloads
Oracle WebLogic Server Installer for Linux
Oracle Database 10g Express Edition for Linux
Platform virtualization is used by cloud service providers such as Amazon Web Services (AWS) to provide remote access to software running on shared hardware infrastructure. Platform virtualization uses the concept of machine images, which can be hosted virtually on remote platforms, allowing users unrestricted access to the underlying infrastructure.
In this tutorial, you will see how to create a custom virtual machine image prebundled with Oracle WebLogic Server 11g and Oracle Database 10g Express Edition (XE). You will also learn the basics of creating init scripts and configuring services to run at user-defined runlevels. This will enable the created images to fully utilize the on-demand scalability of cloud computing; prebundled applications or services will be able to start servicing requests as soon as the instance starts up.
The process followed in this tutorial is a generic one. The prebundled applications and utilities may be customized according to user preferences or demands. It should also be noted that the created images are not restricted to AWS but are fully compatible with any cloud that uses Xen as the hypervisor layer (for example, Eucalyptus Open Cloud).
(Note: Oracle certifies/supports and licenses many of its products on AWS and also supplies free, prebuilt virtual machine templates for several Oracle products on Oracle Enterprise Linux; see the Cloud Computing Center for a full list.)
Before You Start
This tutorial provides a step-by-step guide to the creation of custom images—including installing applications, configuring the images, writing startup scripts, and configuring services to run at specified runlevels—so that these images are ready to be deployed onto a cloud infrastructure. In this tutorial, we will:
- Prebundle a Centos 5.2 base image with Oracle WebLogic Server and Oracle Database XE
- Install additional packages such as vi, FTP, and necessary dependencies
- Configure networking, password, and so on
- Create init scripts
- Configure services (FTP, networking, and so on) and applications (Oracle WebLogic Server and Oracle Database XE) to run at instance startup
Prerequisites
- Enterprise Linux preinstalled system (CentOS used here)
- Base Linux Image (any one of these):
- Created from scratch (see Welcome > Using Amazon EC2 > Creating and Preparing AMIs > Creating an AMI > Creating a Linux or UNIX AMI > Creating an AMI through a Loopback File)
- Downloaded from www.stacklet.com (in the case of CentOS) or edelivery.oracle.com/linux in the case of Oracle Enterprise Linux
- Unbundling a public AMI from AWS using ec2-unbundle
- Oracle WebLogic Server 11g installer for Linux
- Oracle Database XE for Linux
- Pre-created Domain for Oracle WebLogic Server (CloudDomain.tgz)
- RPM installers of any additional packages to be installed
- Amazon ec2-api-tools
- Amazon ec2-ami-tools
- Eucalyptus Cloud setup on local infrastructure or access to AWS
Mounting the Base Image Using Loopback
Resize the image file
The base image file may not have sufficient storage space for accommodating custom applications, so we may need to resize it. We can resize it to suit our own requirements. Here we will resize a 1GB image to 4GB:
[root@localhost Image]# ls -s
total 1026032
1026032 centos.5-2.img
[root@localhost Image]# dd if=/dev/zero of=
centos.5-2.img bs=1M conv=notrunc count=1 seek=4000
#This resizes the image to 4GB.
[root@localhost Image]# losetup /dev/loop1
centos.5-2.img
#loop1 had to be used as xen was already running a different domU via loop0.
[root@localhost Image]# e2fsck -f /dev/loop1
[root@localhost Image]# resize2fs /dev/loop1
[root@localhost Image]# e2fsck -f /dev/loop1
[root@localhost Image]# losetup -d /dev/loop1
[root@localhost Image]# ls -s
total 4100032
4100032 centos.5-2.img
Mount the image file through loopback
The resized image file can now be mounted into a local mount-point so that it can be modified and configured according to our requirements. We will also mount the local processor into the ./mount-point/proc folder so that it functions as the temporary processor for the duration of our exercise.
#make a mountpoint mkdir centos #Mount Image mount -o loop ./centos.5-2.img ./centos #Mount the Proc mount -t proc none ./centos/proc/
Install additional packages
The mounted base image will contain the minimal set of packages needed to support a root file system (Centos 5.2 in our case). Additional packages can be added to provide extra functionalities. Here we will install three sets of additional packages: vsftpd Server (a popular FTP server for UNIX like systems), vi (the popular command line text editor), and dependencies required for Oracle Database XE.
Note: For this tutorial, the following RPMs should be downloaded:
vim-common-7.0.109-3.el5.3.i386.rpm (vi Editor)
vim-minimal-7.0.109-3.el5.3.i386.rpm (vi Editor)
logrotate-3.7.4-8.i386.rpm (dependency for vsftpd)
vsftpd-2.0.5-12.el5.i386.rpm (vsftpd)
libaio-0.3.96-7.i386.rpm (dependency for Oracle Database XE)
bc-1.06-21.i386.rpm (dependency for Oracle Database XE)
#Install Additional Packages
[root@localhost Image]# rpm --root=/home/kiran/Oracle/Image/centos -Uvh
/home/kiran/Oracle/Image/RPMs/vim-common-7.0.109-3.el5.3.i386.rpm
Preparing... ########################################### [100%]
1:vim-common ########################################### [100%]
[root@localhost Image]# rpm --root=/home/kiran/Oracle/Image/centos -Uvh
/home/kiran/Oracle/Image/RPMs/vim-minimal-7.0.109-3.el5.3.i386.rpm
Preparing... ########################################### [100%]
1:vim-minimal ########################################### [100%]
[root@localhost Image]# rpm --root=/home/kiran/Oracle/Image/centos -Uvh
/home/kiran/Oracle/Image/RPMs/logrotate-3.7.4-8.i386.rpm
Preparing... ########################################### [100%]
1:logrotate ########################################### [100%]
[root@localhost Image]# rpm --root=/home/kiran/Oracle/Image/centos -Uvh
/home/kiran/Oracle/Image/RPMs/vsftpd-2.0.5-12.el5.i386.rpm
Preparing... ########################################### [100%]
1:vsftpd ########################################### [100%]
#Install XE Dependencies
[root@localhost Image]# rpm --root=/home/kiran/Oracle/Image/centos -Uvh
/home/kiran/Oracle/Image/RPMs/libaio-0.3.96-7.i386.rpm
warning: /home/kiran/Oracle/Image/RPMs/libaio-0.3.96-7.i386.rpm:
Header V3 DSA signature: NOKEY, key ID 025e513b
Preparing... ########################################### [100%]
1:libaio ########################################### [100%]
[root@localhost Image]# rpm --root=/home/kiran/Oracle/Image/centos -Uvh
/home/kiran/Oracle/Image/RPMs/bc-1.06-21.i386.rpm
Preparing... ########################################### [100%]
1:bc ########################################### [100%]
Working Inside chroot jail
Move Oracle Database XE installer and Oracle WebLogic Server (installers +pre-created domain .tgz) into the image mount-point
Installation of Oracle Database XE and Oracle WebLogic Server will be done from inside the image mount-point. Before doing so, these installers and necessary files need to be moved into the necessary folder inside the image mount-point. We will create a folder (./centos/root/install) inside the image mount-point.
[root@localhost Image]# mkdir ./centos/root/install #Moving the Oracle XE RPM [root@localhost Image]# mv /home/kiran/Oracle/Image/RPMs/ oracle-xe-univ-10.2.0.1-1.0.i386.rpm ./centos/root/install/ #Moving the Oracle Weblogic Binary Installer [root@localhost Image]# mv /home/kiran/Oracle/Image/RPMs/wls1031_linux32.bin ./centos/root/install/ [root@localhost Image]# mv /home/kiran/Oracle/Image/RPMs/CloudDomain.tgz ./centos/root/install/
Change root to mount-point
The image mount-point (./centos) that has been created contains all the files and directory structure needed for a fully functioning base Linux system. We can now reroot into this directory using the chroot command. This directory is called "chroot jail."
[root@localhost Image]# cd ./centos [root@localhost centos]# chroot . bash-3.2#
Change root password for the image and configure remote root login
Here we will set a custom password for root user and configure ssh to allow root login. (Note: For high-security applications, this is discouraged. Use SSH Key-Pairsinstead.)
#Set root Password bash-3.2# pwconv bash-3.2# passwd Changing password for user root. New UNIX password: Retype new UNIX password: passwd: all authentication tokens updated successfully.For allowing remote root login, change PermitRootLogin no to PermitRootLogin yes inside the file /etc/ssh/sshd_config.
Installing and Configuring Oracle Database XE
Install Oracle Database XE RPM
We will now install Oracle Database XE from the installer present in /root/install in the jail.
bash-3.2# rpm -Uvh /root/install/oracle-xe-univ-10.2.0.1-1.0.i386.rpm Preparing... ########################################### [100%] 1:oracle-xe-univ ########################################### [100%] Executing Post-install steps... You must run '/etc/init.d/oracle-xe configure' as the root user to configure the database. bash-3.2# rm -rf /root/install/oracle-xe-univ-10.2.0.1-1.0.i386.rpm 5.2 Configure Oracle Database Express Edition by running /etc/init.d/ oracle-xe configure Run /etc/init.d/oracle-xe configure to open the command-line Oracle configuration wizard. Remember to enter "y" for the question "Do you want Oracle Database 10g Express Edition to be started on boot (y/n) [y]:" if you want the Oracle Database Express Edition service to be started at instance boot. #Configure Oracle XE bash-3.2# /etc/init.d/oracle-xe configure Oracle Database 10g Express Edition Configuration ------------------------------------------------- This will configure on-boot properties of Oracle Database 10g Express Edition. The following questions will determine whether the database should be starting upon system boot, the ports it will use, and the passwords that will be used for database accounts. Press <enter> to accept the defaults. Ctrl-C will abort. Specify the HTTP port that will be used for Oracle Application Express [8080]:8080 Specify a port that will be used for the database listener [1521]:1521 Specify a password to be used for database accounts. Note that the same password will be used for SYS and SYSTEM. Oracle recommends the use of different passwords for each database account. This can be done after initial configuration: Confirm the password: Do you want Oracle Database 10g Express Edition to be started on boot (y/n) [y]:y Starting Oracle Net Listener...Done Configuring Database...Done Starting Oracle Database 10g Express Edition Instance...Done Installation Completed Successfully. To access the Database Home Page go to http://127.0.0.1:8080/apex
Add required environment variables accessible at startup
Scriptlets that are run at instance startup are contained in rc.local. Necessary environment variables like ORACLE_BASE and ORACLE_HOME need to be present for Oracle Database XE to access these at runtime.
Edit /etc/rc.local and add the following lines: ORACLE_HOME = /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/ ORACLE_BASE = /usr/lib/oracle/xe/app/oracle/ PATH=$PATH:/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/bin:$HOME/bin export PATH export ORACLE_HOME export ORACLE_BASE
Installing and Configuring Oracle WebLogic Server
Run Oracle WebLogic Server binary installer
The binary installer that was copied into /root/install folder will now be used to install Oracle WebLogic Server:
#Install WebLogic bash-3.2# chmod +x /root/install/wls1031_linux32.bin bash-3.2# /root/install/wls1031_linux32.bin ########### Follow the steps in the Command Line Installation Wizard ######## bash-3.2# rm -rf /root/install/wls1031_linux32.bin
Oracle WebLogic Server will now be present under /root/Oracle/Middleware/.
Unpack the pre-created domain into /user_projects/domains/
We will be using a domain created on a local machine instead of manually creating one. A domain can also be manually created by using the script /root/Oracle/Middleware/wlserver_10.3/common/bin/config.sh.
#Move CloudDomain.tgz into folder and extract bash-3.2# mkdir -p /root/Oracle/Middleware/user_projects/domains/ bash-3.2# mv /root/install/CloudDomain.tgz /root/Oracle/Middleware /user_projects/domains/ bash-3.2# cd /root/Oracle/Middleware/user_projects/domains/ bash-3.2# tar -xzvf CloudDomain.tgz bash-3.2# rm -rf CloudDomain.tgz
This domain is now ready to be started using the script /root/Oracle/Middleware/user_projects/domains/CloudDomain/bin/startWebLogic.sh.
Create init Script for Starting Domain at Instance Startup
On-demand scalability provided by the cloud necessitates application startup during instance boot, with minimal user interaction. Once a new instance is booted up on the cloud, it should immediately be able to start servicing requests coming to it. For custom applications to fully utilize this capability, they need to be set as services, initialized and running at system boot-up.
Let us create an init script for starting our Oracle WebLogic Server Domain at instance startup. In the init script shown below, I have taken /root/Oracle/Middleware/user_projects/domains/CloudDomain/bin/startWebLogic.sh as the script to start the domain and /root/Oracle/Middleware/user_projects/domains/CloudDomain/bin/stopWebLogic.sh as the script to stop the domain. The script created is named as initWeblogic and is put into the /etc/init.d/ directory.
#################Script Start#########################
#!/bin/sh
#
# chkconfig: 345 99 10
# description: Custom Script
#
SCRIPT_CMD="/root/Oracle/Middleware/user_projects/domains/CloudDomain
/bin/startWebLogic.sh"
SCRIPT_STOP="/root/Oracle/Middleware/user_projects/domains/CloudDomain
/bin/stopWebLogic.sh"
if [ -f /etc/init.d/functions ]; then
. /etc/init.d/functions
elif [ -f /etc/rc.d/init.d/functions ]; then
. /etc/rc.d/init.d/functions
else
exit 0
fi
. /etc/sysconfig/network
[ ${NETWORKING} = "no" ] && exit 0
RETVAL=0
start() {
echo -n "Starting WebLogic "
$SCRIPT_CMD &
RETVAL=$?
[ $RETVAL -eq 0 ] && success || failure
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/myWebLogic
echo
return $RETVAL
}
stop() {
echo -n $"Stopping WebLogic "
$SCRIPT_STOP
RETVAL=$?
[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/myWebLogic
echo
return $RETVAL
}
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
start
;;
*)
echo "Usage: $0 {start|stop|restart}"
exit 1
;;
esac
exit $RETVAL
#################Script End#########################
This script is reusable and can be used to add any custom application into init.d directory.
Activating/Deactivating Services for Specific Runlevels
Services that start automatically at specific runlevels are specified in chkconfig. The following sequence must be followed:
- Add a service to chkconfig --list (if it is not already present)
- Specify runlevels at which the specific service should be on/off
The process is detailed below:
bash-3.2# chkconfig --add initWeblogic bash-3.2# chkconfig --level 345 initWeblogic on bash-3.2# chkconfig --level 345 oracle-xe on bash-3.2# chkconfig --level 345 vsftpd on bash-3.2# chkconfig --list initWeblogic 0:off 1:off 2:off 3:on 4:on 5:on 6:off mcstrans 0:off 1:off 2:on 3:on 4:on 5:on 6:off netconsole 0:off 1:off 2:off 3:off 4:off 5:off 6:off netfs 0:off 1:off 2:off 3:off 4:off 5:off 6:off netplugd 0:off 1:off 2:off 3:off 4:off 5:off 6:off network 0:off 1:off 2:on 3:on 4:on 5:on 6:off oracle-xe 0:off 1:off 2:on 3:on 4:on 5:on 6:off rdisc 0:off 1:off 2:off 3:off 4:off 5:off 6:off sshd 0:off 1:off 2:on 3:on 4:on 5:on 6:off syslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off vsftpd 0:off 1:off 2:off 3:on 4:on 5:on 6:off
This will enable the services initWeblogic, oracle-xe, and vsftpd to start at boot-up and be ready for servicing requests as soon as a new instance of this particular image is created on the cloud.
Stopping Services and Unmounting the Image
Stop the services that were started during image creation, and exit from chroot jail
Services started inside the chroot jail and accessing resources from inside the rerouted folder will make the umount command used to unmount these files back to the image throw a "device busy: error. So let?s stop all the services that were started inside the chroot jail:
bash-3.2# service oracle-xe stop Shutting down Oracle Database 10g Express Edition Instance. Stopping Oracle Net Listener. bash-3.2# service vsftpd stop Shutting down vsftpd: [ OK ] bash-3.2#exit exit [root@localhost centos]#
Unmount the modified file system back to the image
This is the last step for giving you a single image file (centos.5-2.img) ready to be bundled and uploaded into AWS:
[root@localhost centos]# cd .. [root@localhost Image]# umount ./centos/proc/ [root@localhost Image]# umount ./centos
Bundle Image and Upload It into AWS
Bundle image using ec2-bundle-image
[root@localhost Image]#ec2-bundle-image -i ./centos.5-2.img -k <your ec2-key> -c <your ec2-cert> --user <your AWS-user-id>
Refer to AWS docs for further information.
Upload bundle using ec2-upload-bundle
[root@localhost Image]#ec2-upload-bundle -b OracleBucket -m /tmp/centos.5-2.img.img.manifest.xml -a <your ec2-key> -s <your secret-key>Refer to AWS docs for further information.
Register image
[root@localhost Image]# ec2-register OracleBucket/centos.5-2.img.img.manifest.xml -k <your ec2-key> -c <your ec2-cert> --user <your AWS-user-id>
Once the image has been registered in AWS, it becomes an Amazon Machine Image (AMI). We can start an instance of this AMI on EC2. Once this instance boots up, it will automatically start all the services that we have configured to run during startup. Thus, once this instance is running, we will be able to directly access Oracle Database XE and Oracle WebLogic Server hosted on the newly created domain.
Screenshots
Oracle Database XE is hosted at http://<cloud-domain>:8080/apex.
Conclusion
In this tutorial, we saw how to create a custom virtual machine image prebundled with Oracle WebLogic Server 11g and Oracle Database XE. We also learned the basics of creating init scripts and configuring services to run at user-defined runlevels. The approach taken here, being generic, can be used to create custom prebundled images or to modify existing AMIs to provide additional functionalities or to better utilize the on-demand scalability of PaaS clouds.
Kiran C. Nair specializes in JEE, client-server architecture, and performance lifecycle analysis at SETLabs, the research wing of Infosys Technologies Ltd.
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