[CALUG] /etc/hosts not used?

[Rajiv Gunja]

Yup, nsswitch.conf does exactly that. It instructs the OS and all its
commands/system calls to a certain order, when it comes to looking up the
network or any such protocol, which needs to leave/cannot find on the local
host. I am surprised that people would write scripts first before looking at
this file which pretty much does what they wanted/needed. hmm ......

-GGR



---
Rajiv G Gunja
System Analyst / Engg
SUN / AIX / HPUX / Linux Admin
IM: AOL / Yahoo / MSN : ggvrsn

On 3/19/06, Eldon Ziegler <eldonz39yid at yahoo.com> wrote:
>
> In looking for a command to use in a shell script that would first
> search /etc/hosts and then DNS I didn't want to reinvent the wheel
> but, in this case, there doesn't seem to be a wheel so I wrote a C
> routine to printf the result of gethostbyname () which seems to do
> the search in the order I want.
>
> I haven't been able to find a case in which  /etc/host.conf affects
> the search order of gethostbyname. I tried "order hosts,bind" and
> "order bind,hosts" and even "order bind" but gethostbyname returned
> the IP address in /etc/hosts in every case. For me that's fine but I
> don't see how that behavior matches the description in the man page
> for host.conf. An then there is nsswitch.conf?
>
> At 04:47 pm 3/18/2006, Jeremy Portzer wrote:
> >On Sat, 18 Mar 2006, Jim Bauer wrote:
> >
> > > On Saturday 18 March 2006 07:12, Eldon Ziegler wrote:
> > > > I need a local host name to IP address association to override that
> > > > provided by DNS. However, after entering the new definition in
> > > > /etc/hosts the "host" command still returns the IP address from DNS.
> > > > I've tried in on Linux 2.6 (RedHat ES4) and 2.4 (RedHat 9.x).
> > > >
> > > > /etc/host.conf has "order hosts,bind". /etc/nsswitch.conf has
> "hosts:
> > > > files dns". Does some service need to be restarted? How do I get
> > > > /etc/hosts to override DNS?
> > >
> > > I am fairly certain the host command only does DNS lookups.
> > > So it'll never look in /etc/hosts.
> > >
> > > I think you really want to know what does the gethostbyname() library
> > > routine will return?  Try this to find out (replacing 'foo' with what
> > > you want to lookup).
> > >
> > > perl -e '($x) = gethostbyname("foo"); print $x, "\n"'
> >
> >
> >It's not quite that simple.  gethostbyname() returns a list context with
> >several different things, the first argument is the hostname, so the
> above
> >simply returns whatever you give it.  Check the perlfunc and
> >gethostbyname() man pages for the full scoop.
> >
> >Here's a web site that explains how to do this properly in Perl using the
> >Socket library:
> >
> >http://www.unix.org.ua/orelly/perl/cookbook/ch18_02.htm
> >
> >However that doesn't answer the original question of a simple shell
> >command to do a hostname lookup using the system resolver library.  It
> >seems like there ought to be an easy answer for this, but the only thing
> I
> >can think of is to parse the output of "ping" which can be difficult.
> >
> >Here's one ugly attempt at this:
> >
> >ping -n -c 1 foo | head -n 1 | cut -d ' ' -f 3 | sed 's/[()]//g'
> >
> >If "foo" is an unknown host, ping writes that to standard error, so you
> >have to be prepared to handle that too.
> >
> >--Jeremy
> >
> >--
> >/---------------------------------------------------------------------\
> >| Jeremy Portzer        jeremyp at pobox.com      trilug.org/~jeremy     |
> >| GPG Fingerprint: 712D 77C7 AB2D 2130 989F  E135 6F9F F7BC CC1A 7B92 |
> >\---------------------------------------------------------------------/
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