Re: Resolvconf -- a package to manage /etc/resolv.conf

[Neil Roeth <neil@debian.org>]

On Sep 28, Manoj Srivastava (srivasta@debian.org) wrote:
 > On Fri, 26 Sep 2003 21:37:21 +0200, Thomas Hood <jdthood@yahoo.co.uk> said: 
 > 
 > > On Fri, 2003-09-26 at 20:25, Manoj Srivastava wrote:
 > >> I have a laptop that sometimes is on fixed ip wireless
 > >> networks. Since dhcp is not involved, there is nothing that updates
 > >> resolvconf, which could be pointing to an inaccurate set of
 > >> servers.
 > 
 > > If you bring the interface up with ifup then the solution is to put
 > > the nameserver address on a "dns-nameservers" line in the interface
 > > definition stanza.  E.g.,
 > 
 > 	I use that for my non-pcmcia interface.
 > 
 > > You must be referring to /etc/pcmcia/network.opts here.  Hmm, yes.
 > > If you are using the /etc/pcmcia/ stuff to configure PCMCIA network
 > > interfaces then this is a sensible thing to do.
 > 
 > 	Well, I've been using pcmcia way before there was hotplug, but
 >  I'm willing to learn.
 > 
 > 
 > > My own preference is to disable everything in
 > > /etc/pcmcia/network.opts and set things up so that hotplug does ifup
 > > and ifup configures the interface in the standard way.  Then I can
 > > use dns-nameservers lines for PCMCIA network interfaces too.
 > 
 > 	I would be interested in knowing how you set it up  equivalent
 >  to cardctl scheme allows me to set up pcmcia networks. Please mail e
 >  offlist if you wish.

I switched from using cardctl to hotplug earlier this year.  I didn't care to
use any of the packages that do automatic detection of the network, so I set
up a system just like cardctl scheme that allows me to choose which scheme to
use manually.  I no longer have pcmcia-cs installed at all.  I just execute
"hpscheme default" or "hpscheme bs9" and then plug the card in.  It works from
there (don't expect any beeps, though).

I put this in /etc/network/interfaces:

------------------------------------------------------------------------
mapping hotplug
        script /usr/local/bin/map-scheme

iface default inet static
        address ppp.ppp.ppp.ppp
        netmask 255.255.255.0
        gateway qqq.qqq.qqq.qqq

iface bs9 inet static
        address nnn.nnn.nnn.nnn
        netmask 255.255.255.128
        gateway mmm.mmm.mmm.mmm

iface dhcp inet dhcp
------------------------------------------------------------------------

The "mapping" stanza is what figures out which interface to associate with
eth0, i.e., default, bs9, or dhcp.  Here is the script
/usr/local/bin/map-scheme:

------------------------------------------------------------------------
#!/bin/bash

# Used with /etc/network/interfaces mapping function, which passes the
# interface name as the first argument.

/usr/local/bin/hpscheme get
------------------------------------------------------------------------

Here is the script /usr/local/bin/hpscheme:

------------------------------------------------------------------------
#!/bin/bash -e

# Set or display a scheme, used by my hotplug setup to choose network settings
# for PCMCIA card.  Similar to what 'cardctl scheme' did in old pcmcia-cs pkg.

DIR=/var/lib/hpscheme
FL=${DIR}/scheme
[ -d ${DIR} ] || mkdir -p ${DIR}
[ -f ${FL} ] || echo default>${FL}

USAGE="USAGE: $(basename $0) {get|put <scheme>}"

if [ $# -lt 1 ]; then
    echo "$USAGE"
    exit 1
elif [ "$1" = "get" ]; then
    cat ${FL}
elif [ "$1" = "put" ]; then
    echo "Current scheme is '$(cat ${FL})'; setting to '$2'" && echo $2>${FL}
else
    echo "$USAGE"
    exit 1
fi
------------------------------------------------------------------------

You can also add dns-search and dns-nameservers lines to the stanzas in
/etc/network/interfaces if you are using resolvconf, or add scripts to
if-up.d/ and if-down.d/ to muck about with resolv.conf, or whatever you like.
I've done both, though I just switched to resolvconf (thanks, Thomas!).

In addition, of course, you need to set up hotplug, i.e., compile your kernel
with the appropriate options and drivers, etc.

-- 
Neil Roeth