Re: How to get IP address of named host?

On Tue, 28 Feb 2006 15:35:22 +0000, Dave Love wrote:

Without entries in /etc/hosts &c, NSS can effectively lie about DNS, due
to what appears to be highly ill-advised default persistent caching in
nscd. That can cause chaos at boot time if, say, your LDAP servers change
IP and it's a nightmare to diagnose if you don't know about the
(undocumented, as far as I remember) caching and just use `host' to check
that the change propagated in DNS...

I havn't seen a default nscd.conf with caching on for hostnames for years,
not even on Solaris. I think Solaris 7 was the last they shipped with
it defaulting to enabled. And I don't think I've ever seen a Linux
distro ship with it on by default. Yes, you can turn it on but if your
nameservers are performing properly there's no point, and if they are not
it is them you should fix.

And in what way is nscd's caching "undocumented"? That's what it does, it
stands for "Name Service Caching Daemon".

Having said that I consider running nscd to be undesirable in most
circumstances and I cannot understand why some Linux distros ship with it
enabled by default. It may be of use if you are using NIS/NIS+ and have an
enormous user database. But you should have to deliberately enable it IMO.
You should never need it for hosts if you use DNS. It has caused me
problems in the past in SUSE, not with hostnames as this is off by
default, but with usernames and passwords in a NIS environment. SUSE seem
to have changed their minds about nscd, it isn't installed by default in
SLES9 but was in SLES8.

Regards, Ian
.

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