Hi,
We have a strange problem that I never experienced before and cannot
explain, but doesn't seem to be the right behavior nevertheless.
When you resolve a hostname on RHEL5 (RHEL4 is affected too) that is in
/etc/hosts, libresolv performs a DNS lookup. If your DNS is unavailable
for whatever reason, it takes a long timeout for DNS before it returns the
answer from /etc/hosts...
This is easy to verify:
- Add a fake name to /etc/hosts
1.2.3.4 testsys
- Make sure /etc/nsswitch.conf has
hosts: files dns
- Add a non-working DNS server at the top of /etc/resolv.conf
nameserver 4.3.2.1
- Perform a namelookup and see that it times out
getent hosts testsys
getent hosts 1.2.3.4
- Verify that a namelookup is not performed when doing
getent hosts
Even when you configure /etc/nsswitch to do:
hosts: files [SUCCESS=return] dns
it fails to work as we would expect. What am I not understanding ?
From stracing the getent lookups it is clear it opens /etc/hosts first
then does a DNS lookup and then opens /etc/hosts again before printing the
answer.
Does anyone know what is going on ?
Thanks in advance,
--
-- dag wieers, [email protected], http://dag.wieers.com/ --
[Any errors in spelling, tact or fact are transmission errors]
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