Learning something new every day…

My IT experience reaches far back into last century’s 80ies, but no matter how deep I delve into the various subjects, there’s always something new to learn, every day. Like this tiny bit of information that I want to share with you today: I was updating RPMs on a live server, in preparation for a scheduled maintenance later that week. Usually I see that program files and configurations get updated during the installation of the patches, but the services remain active (and will run off the original versions of the files). It definitely isn’t best style to pre-update this way, but may help you to save tremendous amounts of time, especially if you have to update quite a number of systems simultaneously. Like in my case, a larger set of virtual machines, running in a Pacemaker cluster of Xen servers… Those Xen servers, of course, were in for updates as well. But during installation of the openais update, I noticed that the post-installation script tried to restart that service, with almost fatal consequences to the clustered resources on that node!

I had never before experienced this before and reported it back to SUSE, asking for at least a “master switch” to disable such restarts. The answer was almost immediate: The master switch is already there.

In /etc/sysconfig/services, you will find two settings that control this type of behaviour:

## Path: System/Services
## Type: yesno
## Default: no
# Do you want to disable the automatic restart of services when
# a new version gets installed?

## Type: yesno
## Default: no
# Do you want to disable the automatic shutdown of services when
# the corresponding package gets erased?

So in my case, it’s “DISABLE_RESTART_ON_UPDATE” that I need to set to “yes”.

I ran a query in my favorite search engine and learned two things from its results:

  1. This feature reaches back to 2008, support for this had been in YaST2 at least from version yast2-2.17.42.
  2. No obvious pointers to any form of documentation for this feature were returned.

So at least I’ve not been missing something obvious, especially since despite my searches, I could not find any YaST2 menu to manipulate these settings (other than the “sysconfig editor”).

Let me finish with a recommendation for any production system running SLES: Set DISABLE_RESTART_ON_UPDATE=”yes”. Many updates won’t even try to restart after update and those that will, hopefully are programmed to recognize and respect that /etc/sysconfig/services setting!

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