A standard install media, (let’s talk about a DVD for easier start) has several files/folders at his root, but most important are:
isolinux(where the loader lives)
images(for extra files for installer to load)
Packagesfor installation (
Usually, a distribution has, for its main binaries, more than 2 gigabytes of data, that enables one target to act as a multifunction server/workstation, but that you will not usually load on the same system. Furthermore, since the DVD creation, there have been so many updates/patches that make your installation a ‘outdated’ install that you’ll need to upgrade to have recent patches.
Wouldn’t it be better to have one install media suited for your target systems with all available updates applied?
First, we’ll need to copy all of our DVD media to a folder in our hard drive, including those hidden files on DVD root (the ones telling installer which CD-sets are included and some other info).
Let’s assume that we’ll work on /home/user/DVD/
After we’ve copied everything from our install media, we’ll start customizing :)
DVD background image at boot prompt¶
We can customize DVD background image and even keyboard layout by tweaking
isolinux/isolinux.cfg with all required fields (Check
Syslinux Documentation to check proper syntax)
Kickstart: instalaciones automatizadas para anaconda (Spanish) you can also check how to create a kickstart, so you can embed it on this DVD and configure
isolinux.cfg to automatic provision a system
The easiest way would be to install a system with all required package set from original DVD media, and then connect that system to an update server to fetch but not install them.
up2date -du # yum upgrade —downloadonly
yum upgrade —downloadonly
After you download every single update, you’ll need to copy them to a folder like
Well, now let’s start the funny work:
For each package in updates/, you’ll need to remove old version from original folder (remember:
RedHat/RPMS ), and place in that folder the updated one…
After some minutes, you’ll have all updates in place… and you can remove the DVD/updates/ folder as it will be empty after placing each updated RPM in the folder where the previous versions was.
Removing unused packages¶
Well, after having everything in place, we’ll start removing unused files. Usually, we could check every package install status on ‘test’ system by checking rpm, but that’s going to be a way lengthy task, so we can ‘automate’ it a bit by doing:
- If you have
sshpassword-less connection between your systems (BUILD and TARGET):
On BUILD system:
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- If you don’t have
sshpassword-less setup (using private/public key authentication or Kerberos), you can do something similar this way:
On BUILD system:
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Then copy that file on your TARGET system and running:
On TARGET system:
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After you finish, you’ll have a file named
things-to-do, in which you’ll see commands like
If you’re confident about it’s contents, you can run
sh things-to-do and have all ‘not installed on TARGET’ packages removed from your DVD folder.
Adding extra software¶
In the same way we added updates, we can also add new software to be deployed along base system like monitoring utilities, custom software, hardware drivers, etc, just add packages to desired folders before going through next steps.
After all our adds and removals, we need to tell installer that we changed packages, and update it’s dependencies, install order, etc.
This one is trickier, but it is still possible in a not so hard way, first of all, we need to update some metadata files (
hdlist) and Package order for installation, it can be difficult if we add extra packages, as we’ll have special care:
Generate first version of
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Review order.txt to check all packages added by hand to check correct or include missing packages and then continue with next commands:
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createrepo we’ll recreate metadata, but we’ve to keep care and use comps.xml to provide ‘group’ information to installer, so we’ll need to run:
At this step you’ll have a DVD structure on your hard drive, and just need to get an ISO to burn and test:
Now, it’s time to burn MyCustomISO.iso and give it a try ;-)
Post Datum: While testing is just better to keep using rewritable media until you want to get a ‘release’