Subject: Re: HEADS UP: nsswitch about to go `live' in NetBSD-current
To: Wolfgang Rupprecht <firstname.lastname@example.org>
From: Luke Mewburn <email@example.com>
Date: 01/17/1999 17:00:13
Some points (relating to this and other issues):
1. The back-end nsswitch dispatcher (nsdispatch(3)) is a
generic routine. For safety, if /etc/nsswitch.conf is
absent, corrupt, or doesn't have an appropriate entry
for the database requested, a source list of `files'
will be returned.
Whilst it is used by functions such as gethostbyname(3)
for `hosts' lookups, getpwent(3) for `passwd' lookups,
nsdispatch(3) doesn't need to know what the lookups are
because it is generic.
I strongly feel that putting in a hack into a generic
libc routine to provide a specific default of `dns files'
for `hosts' is not the correct orthagonal thing to do.
It reeks of a hack, even if it is to maintain prior
behaviour. I'd object to a similar hack to support
`passwd: compat' by default too.
As I've mentioned a few times; if we
a) ship an working nsswitch.conf in /usr/src/etc that
maintains the behaviour that most people want
b) prompt the user at install time incase they wish to
b) document in the INSTALL notes the the need to have
/etc/nsswitch.conf with `hosts: .. dns ...' to get
then what's the problem? If upgrading user's don't read
INSTALL notes, don't do a diff of etc.tar.gz, and things
don't work then what more can we do to support people
such as them?
2. *If* the dispatch code was modified to provide a default
(as Todd and others ask for), the argument then turns to
``what do you make as the default''?
Some people would want `dns files'.
Others (including myself) would want `files dns', because
it's `safer' (such as when you depend upon lookups to
determine ifconfig/route information, and you have that
in /etc/hosts, otherwise you introduce long delays at
boot as the DNS lookups timeout). Michael K. Sanders also
points out that you have `files dns' to prevent DNS spoofing
of these addresses.
3. Wolfgang Rupprecht mentions:
> Thanks! I was wondering if I was the only one that had a
> fondness for the traditional BSD defaults.
> file-only before named/network is up
> dns-only after named/network is up
> Can't we please at least have the default (if the nswitch
> file doesn't exist) be the current status quo???
As far as I'm aware, the behaviour mentioned (files only
before network is available, dns only after) hasn't been
in use in NetBSD or other systems I've checked such as
Solaris and ULTRIX. In all three cases the lookups remain
the way they were defined at boot time.
If Wolfgang wants the behaviour he mentions he'd have to
add something to /etc/rc which changes /etc/nsswitch.conf
after the networking is up and running.
Alternatively, he could just put `hosts: files dns' in
/etc/nsswitch.conf, and keep /etc/hosts uptodate with those
critical hostnames you need at boot...