RHEL vs OEL: Back in The Cold War?

Posted in: Oracle, Technical Track


I recently encountered a déjà vu on a client system, something I’ve seen repeatedly over the last couple of years. I’ve decided to write about it to prevent others from tumbling down the same rabbit hole.

Red Hat Enterprise Linux 6 system with a Red Hat support contract on it. A DBA had installed Oracle’s oracle-rdbms-server-12cR1-preinstall RPM package. The DBA was doing that based on Oracle support note “Linux OS Installation with Reduced Set of Packages for Running Oracle Database Server (Doc ID 728346.1)” which in the main section simply states:

“For Oracle database 12cR1 running on OL6/RHEL6,use command below to install all packages required for running Oracle software and resolve all dependencies.

yum install oracle-rdbms-server-12cR1-preinstall”

I’ve got a bit problem with how that note was written. Let’s take a look at what exactly happens to your RHEL 6 system, if you do that. First of all, you have to add Oracle’s yum repo to your yum configuration in order to be able to install that package. I’m a firm believer that you should never mix repositories of different Linux distributions on a production server, but I digress.

Then, when you actually install the RPM:

Resolving Dependencies
--> Running transaction check
---> Package oracle-rdbms-server-12cR1-preinstall.x86_64 0:1.0-14.el6 will be installed
--> Processing Dependency: kernel-uek for package: oracle-rdbms-server-12cR1-preinstall-1.0-14.el6.x86_64
--> Processing Dependency: libaio-devel for package: oracle-rdbms-server-12cR1-preinstall-1.0-14.el6.x86_64
--> Running transaction check
---> Package kernel-uek.x86_64 0:2.6.39-400.264.13.el6uek will be installed
--> Processing Dependency: kernel-uek-firmware = 2.6.39-400.264.13.el6uek for package: kernel-uek-2.6.39-400.264.13.el6uek.x86_64
---> Package libaio-devel.x86_64 0:0.3.107-10.el6 will be installed
--> Running transaction check
---> Package kernel-uek-firmware.noarch 0:2.6.39-400.264.13.el6uek will be installed
--> Finished Dependency Resolution

Some DBAs just skip over that section entirely and don’t pay attention to it, but right there Oracle has just installed their own kernel on a RHEL6 system. It’s also been activated and marked as default in grub.conf (which is the norm when installing a kernel RPM):

title Red Hat Enterprise Linux Server (2.6.32-400.37.15.el6uek.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-400.37.15.el6uek.x86_64 ro root=.....
initrd /initramfs-2.6.32-400.37.15.el6uek.x86_64.img

Let that sink in for a minute.

Leaving the system as it is, we’d be going ahead with the installation of the Oracle software, start running our database and go into production. If at any point in the future when we’re be rebooting our server, or if it crashes, we’d suddenly be running the UEK kernel and no longer the Red Hat kernel. There’s also a fairly ugly can of worms awaiting the DBA in question when the SA sees that someone has changed the default kernel.

But the real question is, what would running a different kernel do to us?

Well, Red Hat has an article that’s locked behind a subscriber-only wall. In a nutshell the message it contains is that third party packages are not supported by Red Hat, and third party kernels render all issues unsupported. Fair enough, that makes perfect sense, doesn’t it?

Thus, in essence, we’ve just voided support for our server. If we would hit any issue, we’d have to first clean out any Oracle packages that have replaced Red Hat’s – including the kernel – and reboot the machine back into a clean state, or we’d have to go to the maker of our custom kernel for support. That’s clearly not something you’d want to do during a critical issue on a production server.

If we read the aforementioned Oracle support note a bit more closely, way at the bottom in “Remarks”, as if it’s of no importance, we see this:

“RHEL systems registered with RHN or without an registration with an update channel and which should remain RedHat, can generate a primary list of missing dependencies (manually download the oracle-validated rpm package on public-yum):
# rpm -Uhv oracle-validated–.rpm”

“RHEL systems which should remain RedHat”.

Wait, what?

Doesn’t this basically mean that the note isn’t really telling us how to prepare for Oracle database software installation, but instead it’s telling us how to convert from RHEL to OEL? How to move our support contract over to Oracle?

Also note how the “Applies to” section in that particular note specifically does not include RHEL? It simply says “Linux”. This somehow reminds me of a certain horse that a certain city got as a present at some point in the distant past. Neatly packaged and easy to use, but potentially severe long term impact if you’re installing the package.

I’d like to appeal to both Oracle and Red Hat at this point, please folks, make this more clear. Both sides could do better here. There’s really no reason why solution 55413 should be locked behind a pay wall. It’s often the DBAs who are dealing with these packages to prep for a software install, and they often don’t have access to this content. On a similar note, support note 728346.1 also could be written in a much clearer manner to prevent this sort of confusion. Why is the kernel a dependency of that preinstall RPM? There’s absolutely no need for that.

We’re not in a cold war, are we?

TLDR; Don’t mix repositories of different distributions. Don’t install oracle-rdbms-server-12cR1-preinstall on RHEL unless you’re willing to deal with the consequences.

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About the Author

Stefan is a passionate Oracle database researcher and has been focusing on understanding the Oracle database at its core for more than 10 years. His primary focus lies in the performance of the database, its security aspects, and using its various features to solve problems and architect efficient database designs. Stefan is also an avid technical writer and has written large documentation sets from scratch for massive Oracle projects.

1 Comment. Leave new

A very useful article. I was one of the “Some DBAs”.. I rebooted the server in the build phase shortly after running the pre-req package and it didn’t even come back up! To repeat this articles message: DBAs avoid this package like the plague.


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