An amazing variety of things are keyed off an /etc/hosts entry in Solaris
(including network interface configuration, if memory serves). This man
speaks the truth.
However, I put it to you, world, that if this has only popped up on Sun
boxes, a better solution might be to quietly change solaris.c's method of
determining the hostname. Either changing it to a DNS lookup or by having
it figure out a FQDN by concatenating hostname and the default domain, if
the string it's about to return doesn't contain a dot.
I really hate to build in a dependence on DNS - it makes everything that
much more "fun" when nameservice isn't available...
(then again, in the Sun world you usually place all your eggs in the NIS
basket, so what's the difference? hmmm... )
Jason A. Smith wrote:
I noticed a potential problem that results from the use of the
gethostbyXXX functions. We have a small group of Sun file servers that
we want to monitor with ganglia. The problem originates from having an
/etc/hosts file that includes an entry for your local host that has both
the short and fqdn forms of the hostname defined, like:
xxx.xxx.xxx.xxx host host.domain.name
but no other hosts in your organization. If you have a setup like that,
and the default or standard config in the appropriate /etc/nsswitch.*
config file:
hosts: files dns
then a gethostbyXXX lookup will return the short name for your local
host, but the fqdn for all other hosts in your multicast cluster. This
is obviously a problem because depending on which host in your cluster
gmetad queries, you will end up with one short hostname and the rest
long. Also, if your first host fails to respond to gmetad, then the
next host might be queried resulting in two previously unknown hostnames
that will now be displayed and saved to new rrds. I have been told that
changing the local config is not really an option for us. I an not a
Sun/Solaris admin, but have been told by our admins here that there was
some wierd magic that having your /etc/hosts file configured in this way
solved some strange problems. It may be mostly historical now, but our
admins are understandably reluctant to change an otherwise working
config. I am no expert on this, but others have told me that a better
way to do hostname lookups is to always use DNS lookups (if your
facility is configured to use DNS) through the bind API and not rely on
the local unix config and the gethostbyXXX functions.
~Jason
