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Rolling Your Own: Creating a Custom Incredible PBX ISO for Asterisk

We promised to provide the Incredible PBX 13.2 ISO build environment for those of you that wanted to learn how to roll your own ISO. Why would you want to do such thing? Well, we can think of a number of reasons. First, you may just want to learn how sh*t works. Or you may want to impress your boss by building a custom ISO with the corporate logo splattered all over the place. Then there are those that want to add a feature or function that we haven’t included yet so you can share your creation with your friends. For us, the motivation was to provide an Asterisk® aggregation that others could build upon without legal hassles about copyrights and trademarks… you know, a real open source project based upon the GPL license.

Regardless of your motivation, today’s your lucky day. We’re providing an exact duplicate of the build environment that was used to create the Incredible PBX 13.2 ISO. It’s released under the same GPL license that applies to the ISO itself. Copy it, enhance it, give it to your friends, and share your additions so that all of us can learn from you. In addition to the code, we’re actually going to document how to modify it and use it… you know, real instructions.

The Schmoozers were back in full force last week with one accusing us of "stealing" their code and another with this gem:


For the record, we use GPL code of others with full credit to the authors. That’s what the GPL and Asterisk aggregations have always been about. Let’s compare that to our Sangoma® friends who rip the covers off RedHat’s GPL ISO, brand it as their own, and then have the balls to distribute it as closed source code. Repeating a lie over and over doesn’t make it come true!

Getting Started. Before you can use today’s code, you’ll need a suitable platform on which to play. You’ve got a couple of choices. First, you can actually install Incredible PBX 13.2 using last week’s ISO. A second option is to build yourself a virtual machine or a cloud-based server with Scientific Linux 6.7 or even CentOS 6.7 minimal. We recommend 32-bit architecture because the Incredible PBX 3.2 ISO build environment as configured is 32-bit to assure maximum hardware compatibility. The server hardware platform doesn’t really matter. Cheaper means it takes a little longer, but you’ll get the same results.

Installing the Incredible PBX 13.2 ISO Build Environment. Once you have your server up and running, log in as root. This usually isn’t a good idea for a build environment, by the way. We’re doing it because we’re assuming you have a machine dedicated to just building ISOs on which to experiment. Issue these commands to put the ISO build platform in place:

cd /root
setenforce 0
yum -y install wget nano
wget http://incrediblepbx.com/create-ISO-new.tar.gz
tar zxvf create-ISO-new.tar.gz
rm -f create-ISO-new.tar.gz

Creating Your First ISO. Why waste time? Let’s actually build an Incredible PBX ISO to show you how easy it is. Issue the following command to kick off the process: /root/create-ISO-new. Depending upon your server’s specs, the whole build procedure should take a minute or two to complete. When it’s finished, you’ll have a shiny new ISO that can be burned to a DVD or USB thumb drive following the steps documented in our previous tutorial:

ls -all /root/kickstart_build/*.iso

-rw-r--r-- 1 root root 890241024 Nov 24 12:45 /root/kickstart_build/IncrediblePBX13.2.iso

ISO Design Overview. There are lots of ways to design an ISO architecture. We’ve chosen a hybrid approach with a two-phase install. When you first boot from the ISO installer, you get the operating system platform. The server then reboots, and Phase II downloads and then runs the latest Incredible PBX installer. Our main reason for choosing this design is that you don’t have to create a new ISO every time you make changes in the Incredible PBX installer. For those of you that remember the Asterisk@Home and trixbox days, this was a major shortcoming. The ISOs were released about every three to six months, and invariably a major glitch was discovered about a week after the new ISO was introduced. With our two-phase installer, slipstream changes are easy to implement by simply adding a line to the Incredible PBX install script. The ISO itself never has to be updated until a major operating system refresh is necessary.

Adding Packages to Your ISO. With Incredible PBX, RHEL 6.7-compatible packages are added to new servers in a couple of ways. First, there are packages actually included within the ISO itself that are loaded during Phase I of the install, i.e. when Scientific Linux 6.7 platform is installed. These packages must include all necessary dependencies. The kickstart process actually resolves and loads package dependencies as part of the Phase I ISO install procedure. Once the base install is completed, the end-user’s server reboots and then the Phase II install kicks off by downloading and running the Incredible PBX 13-12R installer. Additional RPM packages and a number of other applications in tarball format are downloaded and installed during this Phase II process. Today, we’ll show you how to modify both pieces of the ISO install procedure.

To add RPMs to the ISO itself, keep in mind that the new RPMs must match the architecture of the default build environment. In the case of Incredible PBX, it’s a 32-bit architecture which means you’ll need 32-bit versions of RPMs you wish to add. Otherwise, you will need to replace all of the packages in the build environment with their 64-bit cousins.

There are 3 steps to adding new packages to the ISO build environment.

First, create a temporary directory (/tmp/packages) to use for gathering up the RPMs to be added. This is so you can check your work without screwing up your build environment. To add an RPM, you first need to download it from a repository to your temporary directory. The syntax looks like this where NetworkManager is the name of the RPM you wish to install:

yum -y install --downloadonly --downloaddir=/tmp/packages NetworkManager

Second, move the RPMs from /tmp/packages into your build environment. This must include RPM package dependencies (as was the case when adding NetworkManager):

mv /tmp/packages/*.rpm /root/kickstart_build/isolinux/Packages/.

Third, add the names of your new RPMs to the kickstart config files (ks*.cfg) in /root/kickstart_build/isolinux. The package names go in the section of each kickstart file labeled %packages.

NOTE: You do not have to add the names of RPMs being added because of dependencies in step 3. You DO have to add the actual RPMs and RPM dependencies in step 2. For example, with NetworkManager, only NetworkManager itself needed to be added to the %packages list in the ks*.cfg config files. But the collection of NetworkManager RPMs and its dependencies for step 2 looked like this:


Changing the ISO Default Boot Menu. Once you have burned the ISO to a DVD-ROM or USB flash drive and booted your server-to-be, a default kickstart menu will be presented: /root/kickstart_build/isolinux/isolinux.cfg. Edit it to customize the splash screen and make any desired changes in the screen title and options displayed to those using your ISO. WARNING: If you modify the ks*.cfg options in the file, you also will need to make similar modifications in the create-ISO-new build script as well as adding new matching ks config files in /root/kickstart_build/isolinux.

Modifying the Phase II ISO Install Procedure. The Phase I install setup already provided in the Incredible PBX ISO will work for any number of ISO requirements you might have because it provides a robust Scientific Linux 6.7 base platform. Now for the fun part. You can modify the Phase II install in any way you like by simply adjusting the download script and hosting it on your own public server.

The Phase II magic is housed in the %post section of the kickstart config files (ks*.cfg). The initial setup in this section will work for almost any setup. It addresses the quirks of getting a working network connection functioning on most server platforms. This got much more complicated with the introduction of UEFI on newer Intel-based servers. But we’ve addressed all of that. To customize the install to run your own Phase II script, you need only modify the last few lines of the %post section:

/bin/echo "cd /root" >> /tmp/firstboot
/bin/echo "/usr/bin/wget http://incrediblepbx.com/incrediblepbx13-12.2-centos.tar.gz" >> /tmp/firstboot
/bin/echo "/bin/tar zxvf incrediblepbx13-12.2-centos.tar.gz" >> /tmp/firstboot
/bin/echo "/bin/rm -f incrediblepbx13-12.2-centos.tar.gz" >> /tmp/firstboot
/bin/echo "./Inc*" >> /tmp/firstboot
/bin/chmod +x /tmp/firstboot

These last few lines tell the ISO installer where to find your Phase II script and manage the procedure for downloading it, untarring it, and then running it. To deploy your own Phase II install script, simply modify lines 2, 3, 4, and 5 above. In line 2, provide the public server location of your script in .tar.gz format. In line 3, untar the script in the /root folder of the new server. In line 4, remove the .tar.gz file after it’s been decompressed. In line 5, run the shell script included in your tarball. The remaining lines shown above should be preserved as shown. Once you finish making changes in ks.cfg, copy the %post section to your other kickstart config files and then rerun /root/create-ISO-new to build your new ISO. Enjoy!

Originally published: Friday, December 11, 2015

Support Issues. With any application as sophisticated as this one, you’re bound to have questions. Blog comments are a terrible place to handle support issues although we welcome general comments about our articles and software. If you have particular support issues, we encourage you to get actively involved in the PBX in a Flash Forums. It’s the best Asterisk tech support site in the business, and it’s all free! Please have a look and post your support questions there. Unlike some forums, ours is extremely friendly and is supported by literally hundreds of Asterisk gurus and thousands of users just like you. You won’t have to wait long for an answer to your question.

Need help with Asterisk? Visit the PBX in a Flash Forum.


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