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Re: [HTCondor-users] $(FULL_HOSTNAME)

On 11/28/2016 5:39 PM, Kandes, Martin wrote:
Hi HTCondor team,

How does HTCondor determine $(FULL_HOSTNAME)? Is there a difference in
how it is determined between EL6 and EL7? I ran into a problem with a
simple, out-of-the-box personal condor pool install not working on EL6
[1] [2], but it is working with no problem on EL7 [3] [4].

I know the problem has something to do with how the local system is
configured. The problem occurs on a CentOS 6 image booted up on a local
OpenStack cluster. However, the error is not observed when I perform the
same install on a CentOS 6 image on AWS.

This is not an urgent matter. But when you get the chance, perhaps you
can provide a possible explanation. I'd like to understand better what
maybe causing the difference in behavior.



Hi Martym

Unfortunately, the answer is complicated, it is different depending upon the version of HTCondor (because things had to change to support IPv6), and is dependent on settings you may have tweaked such as NETWORK_HOSTNAME, NETWORK_INTERFACE, NO_DNS, maybe others.

From my dim memory (warning! this is off the top of my head...), the basic idea is HTCondor figures out which network interface it will use by default (see docs for NETWORK_INTERFACE), and then does an inverse-lookup on the IP address associated with that interface to get a fully qualified hostname. Perhaps your openstack cluster is not setup with inverse address names in DNS, but AWS is? Failure to setup inverse address names is a common site failure, esp if the site recently deployed IPv6. As for why RHEL7 works on openstack, perhaps your RHEL7 image is configured to fallback on using /etc/hosts to do inverse lookup via nsswitch.conf. What does your host file look like on the two images? According to the standards it should be
  address full.hostname.edu alias1 alias2
e.g. the fully qualified hostname should appear first:
GOOD:  chevre.cs.wisc.edu chevre
 BAD:  chevre chevre.cs.wisc.edu

You can gather some insight into what is going on by doing (on bash)

  %  _condor_tool_debug=D_HOSTNAME condor_config_val -debug full_hostname

or if you are running a more recent HTCondor v8.5.x, you could do
  % condor_config_val -debug:D_HOSTNAME full_hostname

hope the above helps,