I have noticed that with my recent restructuring of my cluster's DNS
hierarchy by creating two Service Nodes to stand in between the compute
nodes and the Management Node that I am having two separate problems with
files being overwritten once I modify them.
Firstly, I configured the SNs to act as actual slave DNS servers instead of
just forwarding to the MN (that feature it looks like will be officially
supported in the next xcat release but is not supported in the current
one), so I had to edit /etc/named.conf to facilitate that. Before I edited
that file on both SNs it simply had an options { } block ending with
"forward only" and a "forwarders { }" block with the IP of the MN, but I
removed the "forward only" statement, added zone definitions, and made each
zone a slave to the MN. It worked perfectly. The only problem is that every
couple days (and it happened again this morning) all my changes get erased
somehow and named.conf is regenerated to the default file with only an
options { } block. How can I prevent that from happening?
Secondly, for compute nodes and storage nodes which were dhcp enabled
instead of statically assigned in their
/etc/sysconfig/network-scripts/ifcfg-eth* files, when I manually edited the
/etc/resolv.conf (though a postscript would do the same) it too would get
overwritten fairly soon after I made the change, back to only pointing to
the MN for DNS. I changed the resolv.conf to point not just to the MN (as
they did originally) but created three "nameserver" entries to look for DNS
name servers in the following order: SN1, SN2, MN.
I "fixed" this by statically assigning IPs in the ifcfg-eth* files, but I
am wondering if there is a better way. DHCP has the ability to push out DNS
server names for resolv.conf and so I looked to see if it was the culprit
and I changed the "option domain-name-servers" line to include SN1, SN2,
and the MN (does the "nameservers" value in the xCAT 'site' table set this
line?), but I'm not sure if that is the line for DHCP responsible for
changing the values in /etc/resolv.conf, or how often the DHCP changes were
pushed out (this is happening for machines which are not being rebooted or
reinitialized in any way - just running as normal - and they suddenly
change their resolv.conf).
Are any of the suggestions on this page good options:
http://www.cyberciti.biz/faq/dhclient-etcresolvconf-hooks/? I don't have a
dhclient.conf file on my RHEL/CentOS servers though. Anyway, any
suggestions would be much appreciated!
Thanks,
Josh
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