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  <head>
    <title>Netenv 0.94 - Using a laptop in different network environments</title>
  </head>

  <body>
      <h2><a name="top">Do you use your laptop in different network environments ?</a></h2>

    At home ? In the office ? At a customers site ?
    <p>
      If yes, the small package <i>netenv</i> might be useful for you. When 
      booting your laptop it provides you with a simple interface from 
      which you can choose the current network environment. If you are 
      the first time in an environment, you can enter the basic data
      for later reuse.
    <p>
      <I>Netenv</I> sets up a file containing variable assignments which
      describe the current environment. This can be used by the pcmcia
      setup scheme (e.g. like the one that comes with Debian, RedHat
      and SuSe). If you have a Network Interface Card (often simpy
      called NIC) onboard, you can use the same mechanism. 
    <p>
       Have a look at <i>netenv</i>'s chooser box:
    <p>

<img src="netenv-chooser-box.png">
    <p>

      Besides the basic functionality of configuring the NIC, the <i>netenv</i> data can be used for thinks like:
    <ul>
      <li>Choose a proper XF86Config
	<p>

	Think of using your laptop standalone with touchpad
	vs. connected to a CRT monitor along with an external wheel mouse.
	<p>
      <li>Setting up DNS
	<p>
	  You create the appropriate /etc/resolv.conf.
	<p>
      <li>Printing Environment
	<p>
	  Assigning a proper value for e.g. PRINTER defines a default printer.
	<p>

      <li>Editing your Netscape preferences file
	<p>
          So it's possible to avoid network timeouts, when working not
          connected to the net and viewing only local files.
<p>
      <li>Configuring Fetchmail
	<p>
	  Having a permanent connection to my mailserver I use
	  <i>netenv</i> to call fetchmail as a daemon which fetches mail
	  periodically.
	<p>
      <li>Linking /dev/pilot
	<p>
          If you use a palm, you may link /dev/pilot to a serial
          device when a cradle is connected and to the IRDA-port if
          you are on the road.

    </ul>
    <p>
      <I>Netenv</I> is available prepackaged for Debian and Redhat Linux as
      well as tarball. Mandrake- and SuSe-Users may use the RedHat-RPM.
      <i>netenv</i> depends on dialog(1) resp. gdialog (which comes
      with the mentionend  distributions).
    <p>
A word to all gurus: In this docu I try to explain things with Linux
novices in mind, so be patient.

      <hr>
<p>
<a name="toc">Table of Contents</a>
<p>
<a href="#top">What does <i>netenv</i> do ?</a>
<p>
<a href="#download">Where to get <i>netenv</i> ?</a>
<p>
<a href="#installation">How to install</a>
<p>
<a href="#basics">Basics</a>
<p>
<a href="#firsttimeconfig">First time configuration</a>
<p>
<a href="#config">Configuration</a>
<p>
<a href="#examples">Examples</a>
<p>
<a href="#dns">Remarks at DNS</a>
<p>
<a href="#suse">Remarks for SuSe 7.3 Users</a>
<p>
<a href="#alternatives"><i>netenv</i> alternatives</a>
<p>
<a href="#final">Conclusion</a>
<p>
      <hr>


<h2><a name="download">Where to get <i>netenv</i> ?</h2>

<I>Netenv</I> has a homepage at Sourceforge:

<a href="http://netenv.sourceforge.net">http://netenv.sourceforge.net</a>
    <p>
But you may know this already ...
<p>
You will find there the tar-file as well as the RedHat-RPM. The latter
should be useable in Mandrake and Suse too.
<p>
Debian-User
<p>
<I>Netenv</I> has been available for Debian quite a while. Look at
<a href="http://www.debian.org/distrib/packages">http://www.debian.org/distrib/packages</a>.
<p>
<a href="#toc">Back to Table of Contents</a>

<h2><a name="installation">How to Install</h2>

It depends ... For all distributions, which use RPM, do as root e.g.:

<pre>
rpm -i netenv-0.94-1.i386.rpm
</pre>

In Debian e.g.:

<pre>
dpkg -i netenv-0.92-2.i386.deb
</pre>

In all other cases:

<pre>
tar xvf netenv-0.94-2.tar
</pre>

This installs a shellscript called <kbd>netenv</kbd>,
a little helper utility trpnc, configuration examples and these docs.

Depending on the distribution a little handwork may be necessary.

<h3>RedHat</h3>

<em>I don't know anything about current RedHat versions. Therefore the
following hints are probably out of date. You may find useful hints in
the section <a href="#how-to-use-tar">How to use the tar-file</a></em>
    <p>

The <i>netenv</i>-RPM has been packaged under RedHat 6.1. So it should
be possible to install in all distributions using RPM.
<p>
The postinstall-script puts

    <ul>
      <li>a call to <i>netenv</i> in <kbd>/etc/rc.d/rc.sysinit</kbd>
      <li>and cares for the integration in the NIC's configuration
    </ul>

<kbd>/etc/rc.d/rc.sysinit</kbd> now looks like this:

<pre>
lulu:/home/bav> tail -2 /etc/rc.d/rc.sysinit
# Added by package netenv on 06.03.2000 19:53:10
/usr/sbin/netenv
</pre>

Additionally <kbd>/etc/sysconfig/network-scripts/ifcfg-eth0</kbd> will
be changed. Just after first installing Redhat this file looks like:

<pre>
lulu:/etc/sysconfig/network-scripts>>> cat ifcfg-eth0 
DEVICE=eth0
BROADCAST=192.168.200.255
IPADDR=192.168.200.201
NETMASK=255.255.255.0
NETWORK=192.168.200.0
ONBOOT=yes
</pre>

Installing <i>netenv</i> adds two lines:

<pre>
lulu:/etc/sysconfig/network-scripts>>> tail -3 ifcfg-eth0
ONBOOT=yes
# Added by package netenv on 06.03.2000 19:53:10
if [ -r /tmp/netenv ]; then . /tmp/netenv; fi
</pre>


<h3>SuSe</h3>

With Suse 8.x a couple of changes in system boot and network
configuration were introduced. The current procedure assumes 
Suse 8.1, but it should work with 8.0 as well. For older versions 
see the next paragraph.

<h4><a name="suse-8-1">SuSe 8.1</h4>

The postinstall-script adds two lines to /etc/init.d/boot.local:

<pre>lulu:/etc/init.d> tail -3 boot.local
#
# Added by package netenv on 06.12.2002 10:45:10
/usr/sbin/netenv
</pre>

This way netenv is called during boot. netenv assumes the NIC to be
configured is eth0, so the line

<pre>if [ -r /tmp/netenv ]; then . /tmp/netenv; fi
</pre>

is appended to the file <pre>/etc/sysconfig/network/ifcfg-eth0</pre>
It then looks like:

<pre>lulu:/etc/sysconfig/network> cat ifcfg-eth0
FIREWALL="YES"
BOOTPROTO='static'
BROADCAST='nn.nn.nn.nn'
IPADDR='nn.nn.nn.nn'
NETMASK='nn.nn.nn.nn'
NETWORK='nn.nn.nn.nn'
REMOTE_IPADDR=''
STARTMODE='onboot'
UNIQUE='oxTw.yHaVEFCrUXE'
WIRELESS='no'
if [ -r /tmp/netenv ]; then . /tmp/netenv; fi
</pre>

The entries IPADDR, NETMASK etc. spring from the basic installation.
There is no need to delete them as they are superseded by the
assignments in /tmp/netenv. In this example I assume that the NIC is
not a PCMCIA-NIC. Otherwise the line

<pre>STARTMODE='onboot'</pre>

must read

<pre>STARTMODE='hotplug'</pre>


<h4>SuSe 7.3</h4>

The postinstall-script adds two lines to /etc/rc.d/boot.local:

<pre>
mweb@guru:/etc/rc.d > tail -3 boot.local 
# before we're going to the first run level.
#
# Added by package netenv on 06.02.2001 20:28:10
/usr/sbin/netenv
</pre>

For PCMCIA-Cards an entry in /etc/pcmcia/network.opts
is done: 

<pre>
mweb@guru:/etc/pcmcia > tail -2 network.opts 
esac
# Added by package netenv on 06.02.2001 20:28:10
if [ -r /tmp/netenv ]; then . /tmp/netenv; fi
</pre>

If the laptop has a builtin NIC and PCMCIA must not be used, you may
override the values defined by YAST as follows:

<pre>
mweb@guru:/etc/rc.d > head -16 network 
#! /bin/sh
# Copyright (c) 1996 SuSE GmbH Nuernberg, Germany.  All rights reserved.
#
# Author: Florian La Roche <florian@suse.de>, 1996
#       Werner Fink <werner@suse.de>, 1996
#       Burchard Steinbild <bs@suse.de>, 1996
#       Rolf Haberrecker <rolf@suse.de>, 1998
#       Werner Fink <werner@suse.de> (based on a patch of Andries Brouwer) 1999
#
# /sbin/init.d/network
#

. /etc/rc.status
. /etc/rc.config
if [ -r /tmp/netenv ] ; then . /tmp/netenv; fi
</pre>

<h3>Debian</h3>

The Debian-Package netenv is currently worked on. As far as I know,
PCMCIA-NIC's can be used without further configuration.
    <p>
Onboard-NIC's though need a changed /etc/network/interfaces. You can
do this using netenv procedures, see the example script
netenv_setup_debian_example. If you do nothing, your NIC will be
configured like it was during system installation regardless what you
choose with netenv.

<h3>Mandrake</h3>

Mandrake 9 users reported that the splash-screen had to be disabled
(disable vga=nnn in /etc/lilo.conf) in order to be able to input
something during boot. Furthermore the cdialog seems not to be stable.
Problems could be solved only after using the SuSE dialog binary instead.

<h3><a name="how-to-use-tar">How to use the tar-file</h3>

These are the necessary steps:

<pre>
tar zxvf netenv-0.94-2.tar.gz
cd netenv-0.94-2
make
make install # must be user root from now on !
make config
</pre>

Depending on the distribution the last step <kbd>make config</kbd> may
eventually have to be done manually.
    <p>
netenv must be called <b>before</b> the normal network- or PCMCIA-start.
Check for <kbd>/etc/init.d/boot.local</kbd> or the equivalent. See the
<a href="#suse-8-1">SuSE 8.1</a> paragraph for further details.
<p>
After you have ensured that netenv is called during boot, the
configuration data must be read by the network scripts. Modern
distributions seem to use <kbd>ifup</kbd> to start a preconfigured net
interface. Then the <a href="#suse-8-1">SuSE 8.1</a> paragraph should
contain the details.
    <p>
A common issue is to confuse eth0 and eth1 if there is an onboard NIC
and a PCMCIA NIC. Chances are that eth0 is the onboard and eth1 is the
PCMCIA NIC. Verify with <kbd> dmesg | grep eth</kbd> and <kbd>lspci</kbd>.
    <p>
Netenv checks for eth1, but depending on the configuration at the time
of installation this cannot be waterproof.
    <p>

<a href="#toc">Back to Table of Contents</a>

<h2><a name="basics">Basics</h2>

The basic idea is to enter information about the current location of
the laptop in a very early phase of booting. This happens before
configuring any network interface. 
    <p>
This is done using dialog(1), a simple menu interface, well known to
most users. Booting is continued after the user has done his
selection. For a default environment this may be as simple as just
pressing RETURN.
    <p>

If "lilo" is used as bootmanager, you may alternatively input after
the lilo-prompt:
    <p>
<pre>
linux NETENV=office
</pre>
This defines a shell variable "NETENV" with the value "office". This
means for me: I am with my laptop named lulu in the office. The file
containing the values for IP-address etc. is
/etc/netenv/lulu-lavie. The Linuxkernel starts the init-process
with the variable NETENV as part of its environment. The same does
init with the so called rc-scripts.
<p>
The netenv-script tests for NETENV beeing defined. If it is, netenv
carries out further actions without popping up the manu.
    <p>
After having selected the current environment, netenv copies the
actual file to /tmp/netenv.
<p>
This file has modes 644, so being readable by any user for further
user dependent configuration tasks.
<p>
<a href="#toc">Back to Table of Contents</a>

<h2><a name="firsttimeconfig">First time configuration</a></h2>

After installing the user root should call netenv. Do simply:

<pre>
netenv
</pre>

This will fire up a menu with only one choice:

<pre>
    new  Set_up_new_environment  
</pre>

These parameters will be asked for:
<pre>
   Enter the current IP-Address or the keyword dhcp ...
   Enter the netmask of the current subnet ...
   Enter the IP-Address of the current network ...
   Enter the Broadcast-Address of the current network ...
   Enter the Gateway-Address of the current network ...  
   Enter the IP-address of the current nameserver ...  
</pre>

If in a network with DHCP-Server, input dhcp instead of an
IP-Address. Then a /tmp/netenv is generated containing only

<pre>
BOOTPROTO='dhcp'
STARTMODE='hotplug'
</pre>

All other values will be derived according to the DHCP-configuration.
If the NIC is onboard, netenv should have written
<pre>
STARTMODE='onboot'
</pre>

In case of a static IP-address there will be a default entry for the
other items, which will be sufficient in many situations.
<p>
Finally you will be asked if you want to save this configuration for
further use:
<pre>
    Do you want to save this configuration ?
</pre>

Please <b>do not use spaces</b> in this name !
<p>
Depending on the Distribution netenv offers to restart the network and
to activate the changes this way.
    <p>
If this is not applicable, take out your PCMCIA-NIC (if it's PCMCIA
you use ...) and stick it in again (cardmgr will ring the bell). The
same result may be achieved doing 

<pre>
/etc/init.d/pcmcia restart
</pre>

In any case cardmanager from the PCMCIA-package should configure the interface.
<p>
Ping your gateway-address and you will know !
<p>
Didn't work ? Is the link-LED green ? Check the output of 
<pre>ifconfig eth0</pre>
<p>
The procedure just described may be also be used, wenn you want to
switch from one network environment to another while your laptop stays
up and running. There is no need to reboot - it's Linux ... 
<p>
Those, who use a NIC onboard instead of a PCMCIA-NIC have to restart their
network.
<p>
In RedHat or SuSE e.g.:
<pre>
/etc/init.d/network restart
</pre>

Netenv does this according to your input.
    <p>

<a href="#toc">Back to Table of Contents</a>

<h2><a name="config">Configuration</a></h2>

<I>Netenv</I> is configured using files. You will find them in
<kbd>/etc/netenv</kbd>. On a laptop named "lulu" files 
lulu, lulu-foo, lulu-bar etc. will be used.

So the naming scheme is as follows:
<pre>
/etc/netenv/&lt;NODE-NAME&gt;-&lt;VALUE-OF-VARIABLE-NETENV&gt;
</pre>

The filename identical to the laptop's hostname is the first item in the
selection menu. You simply may press RETURN and booting is continued.
You should put the most frequently used environment into this file.
<p>

All files contain assignments in shell syntax, e.g.

<pre>
netenv_id=At_Home_LCD_WheelMouse_pcmcia
...
IPADDR=123.456.78.9
...
NETSCAPE_PROXY_TYPE=2
</pre>

Spaces will cause trouble. For a well configured NIC you will have to
define at least

<pre>
IPADDR
NETMASK
NETWORK
BROADCAST
</pre>


Depending on the situation you may additionally have to define
<pre>
GATEWAY
DNS_1
</pre>

<b>You may stick any variableassignment into the file - as long as everything
is syntactically right.</b>

There is something special with an assignment like

<pre>
NETENV_SCRIPT=/etc/netenv/netenv_setup
</pre>

If the file pointed to is readable, netenv will
execute this file (to be precise: it will source it) after the current
network environment has been choosen.
    <p>
<b>Pay Attention ! This will be in a very early stage of boot. No
network will be active ! NETENV_SCRIPT will be executed with root privileges !</b> 
    <p>
With the help of this script you may do quite useful things. More on
this in the <a href="#examples">example section</a>.
<p>

<h3>Expert Mode</h3>

If you choose CANCEL in the netenv-dialog-box, you may enter a
shell. After quitting this, the chooserbox pops up again.


<b>Security hints:</b>

The directory /etc/netenv and the files in it must be writeable only 
for root. netenv does some basic checks for this.
<p>
<a href="#toc">Back to Table of Contents</a>

<h2><a name="examples">Examples</a></h2>

Of course this is the most important part of this documentation ...
<p>
The examples are described step by step. So please read them one after
the other !

<h3>StandAlone_Touchpad</h3>

<pre>
lulu:/etc/netenv>>> cat lulu-touch-pad 
netenv_id=StandAlone_Touchpad_no_eth
STARTMODE=manual
export XF86CONFIG_FILE=/etc/X11/XF86Config-4-lcd-touch
NETENV_SCRIPT=/etc/netenv/netenv_setup
# This may be used to edit ~/.netscape/preferences.js
NETSCAPE_PROXY_TYPE=3
</pre>

I use this one when my laptop has no network connection.
<p>
The value of the variable netenv_id (as I said earlier: Please <b>without</b>
spaces) will be used as decription in the chooser box.
<p>
There is no IP-address defined. By setting STARTMODE=manual there will
no  NIC be configured during boot. I assign 
NETENV_SCRIPT=/etc/netenv/netenv_setup. This is a file
containing shell commands. It is attached to this documentation <a href="netenv_setup">here</a>.
    <p>
This sample is written in a simple manner to get you started. Relevant
code section here is:

<pre>
lulu:/etc/netenv>>> cat netenv_setup
...
# Simple way to configure the X-Server 
if [ -r $XF86CONFIG_FILE ]; then
    echo $XF86CONFIG_FILE will be used for configuring the X-Server ...
    mv /etc/X11/XF86Config /etc/X11/XF86Config.old
    ln -s $XF86CONFIG_FILE /etc/X11/XF86Config
fi
fi
...
</pre>

As I defined XF86CONFIG_FILE the code creates a link. Right now it is
pointing to the configuration file, which I created for my laptop with
touchpad.
<p>
Typically netenv_setup does everything the root user is needed for and
the whole system is concerned with. Personal settings are done via
.xinitrc. Here is an example:
<p>
In my private configuration I use NETSCAPE_PROXY_TYPE:

<pre>
lulu:/home/bav> cat .xinitrc
#!/bin/sh
...
if [ -r /tmp/netenv ]; then
. /tmp/netenv
fi
if [ -n "$NETSCAPE_PROXY_TYPE" ]; then
   ~/tools/edit-ns-preferences $NETSCAPE_PROXY_TYPE
fi
...
</pre>

You will find the script edit-ns-preferences in the
<i>netenv</i>-documentation. It will avoid nasty network-timeouts, when
starting the browser.

<h3>In_the_Office</h3>

<pre>
lulu:/etc/netenv>>> cat lulu-lavie
# Networkenvironment: netask
netenv_id="lavie_pcmcia_dhcp"
export BOOTPROTO=dhcp
export STARTMODE=hotplug
export PRINTER=cc_hp
NETSCAPE_PROXY_TYPE=2
FETCHMAIL_POLL_INTERVALL=900
</pre>

In the office I get my network configuration from a
DHCP-Server. STARTMODE=hotplug is set, because my laptop has no onboard-NIC
and therefore the PCMCIA-NIC has to be used.
<p>
PRINTER=cc_hp sets the defaultprinter to the printer in the office. NETSCAPE_PROXY_TYPE=2
activates automatic proxyconfiguration in Netscape.
<p>
When I am in the office, mail shall be fetched periodically. For this 
I use FETCHMAIL_POLL_INTERVALL. The following snippet from my
<kbd>~/.xinitrc</kbd> starts fetchmail as daemon, which will became active every 15 min
and carry out things defined in <kbd>~/.fetchmailrc</kbd>:
<pre>
if [ -n "$FETCHMAIL_POLL_INTERVALL" ]; then 
   fetchmail -d $FETCHMAIL_POLL_INTERVALL
fi
</pre>

<h3>Laptop_at_home</h3>

At home I use my default configuration file. As I work here most of
the time the filename equals my laptops node name. So I just have to
press return in the netenv-chooser-box: 

<pre>
netenv_id=At_Home_Docking_LCD_WheelMouse_onboard_VPN
IPADDR=nnn.nn.nnn.nnn
NETMASK=nnn.nnn.nnn.nnn
NETWORK=nnn.nn.nnn.nnn
BROADCAST=nnn.nn.nnn.nnn
GATEWAY=nnn.nn.nnn.nnn
SEARCH=foo.bar.com
DNS_1=nnn.nn.nn.nn
DNS_2=nnn.nn.nn.nn

FETCHMAIL_POLL_INTERVALL=900

# If the variable NETENV_SCRIPT points to an readable file,
# it will be run when netenv is executed
NETENV_SCRIPT=/etc/netenv/netenv_setup
ICEWM_INCLUDE_FILE=home
# This defines my CRT with 1024x768 and a wheelmouse
XF86CONFIG_FILE=/etc/X11/XF86Config-4-lcd-wheel
# This may be used to edit ~/.netscape/preferences.js
NETSCAPE_PROXY_TYPE=2
# This may be used to edit ~/.opera/opera6.ini
OPERA_PROXY_FILE=proxy-fsc.ini

# NIC is in the docking unit - like it were onboard
STARTMODE='onboot'
</pre>

Relevant portion from my netenv_setup is this:
<pre>
lulu:/etc/netenv>>> cat netenv_setup
...
PROFILE=$1
...
if [ "$PROFILE" = "default" ]; then
   print_action linking /dev/pilot
   rm -f /dev/pilot; ln -s /dev/ttyS0 /dev/pilot
   print_status
   print_action calling ptal-init start
   /usr/sbin/ptal-init start 
   print_status
else
   # When there is no docking station, start irattach appropiately and
   # link /dev/pilot to ircomm0.
   print_action running irattach
   /usr/sbin/irattach /dev/ttyS3 -s
   print_status
   print_status linking /dev/pilot
   rm -f /dev/pilot; ln -s /dev/ircomm0 /dev/pilot
   print_status
fi
...
</pre>

netenv_setup is called with the parameter PROFILE, which equals 
"default" here (in all other cases it is the filename of the
descriptionfile minus hostname portion).  
    <p>
At home I use a cradle for my palm. So /dev/pilot must point to the
appropriate serial device. Additionally the software for my HP
Officejet has to be started. In all other environments the palm can be
reached only via IRDA. ptal must not be started then.
    <p>
At home my laptop is in a docking-unit. This has a NIC. In order to use
this NIC

<pre>STARTMODE='onboot'</pre>

has to be set.

<h3>At_Customer_Foobar</h3>

Earlier versions of libc made it possible  for a non privileged user
to make kind of private /etc/hosts by setting the environment variable
HOSTALIASES. Due to security issues this is no longer possible in
recent versions of libc.
<p>
If you don't like to edit your /etc/hosts manually, the following idea may help.
For me it is useful, as I find computers with identical names but
different IP-addresses in different environments.
<p>
I put marks in my /etc/hosts like this:
<pre>
lulu:/home/bav> cat /etc/hosts
...
# netenv hosts begin
# netenv hosts end
...
</pre>

Now I define nodes with their IP-addresses, which I want to connect to
in the current environments:

<pre>
NETENV_HOST_ENTRIES="192.168.10.11 abba:192.168.10.12 bebe:192.168.10.3  alfa-sw:\
192.168.10.4  beta-sw:192.168.10.13 coca:192.168.10.14 cola"
</pre>

This code in my /etc/netenv/netenv_setup will care for editing /etc/hosts
after choosing the environment:

<pre>
if [ -n "$NETENV_HOST_ENTRIES" ]; then
   if egrep '^# netenv hosts begin$' /etc/hosts > /dev/null 2>&1; then
      (
      awk 'NR==1,/^# netenv hosts begin$/' /etc/hosts
      echo $NETENV_HOST_ENTRIES | awk -F'\:' '{ for ( j=1; j<=NF; j++ ) print $j }'
      awk '/^# netenv hosts end$/,/*/' /etc/hosts
      ) > /etc/hosts.netenv
      mv /etc/hosts.netenv /etc/hosts
      chmod 644 /etc/hosts
      echo netenv_setup: /etc/hosts was modified ...
   fi
else
   if egrep '^# netenv hosts begin$' /etc/hosts > /dev/null 2>&1; then
      (
      awk 'NR==1,/^# netenv hosts begin$/' /etc/hosts
      awk '/^# netenv hosts end$/,/*/' /etc/hosts
      ) > /etc/hosts.netenv
      mv /etc/hosts.netenv /etc/hosts
      chmod 644 /etc/hosts
      echo netenv_setup: /etc/hosts was cleaned up ...
   fi
fi
</pre>

Now /etc/hosts looks like this:

<pre>
...
# netenv hosts begin
192.168.10.11 abba
192.168.10.12 bebe
192.168.10.3 alfa-sw
192.168.10.4 beta-sw
192.168.10.13 coca
192.168.10.14 cola
# netenv hosts end
...
</pre>

All these nodes are trusted, so I use the mechanism in my <kbd>~/.xinitrc</kbd>
and  call xhost appropriate:

<pre>
XHOST_PLUS_LISTE=`awk '/^# netenv hosts begin$/,/^# netenv hosts end$/' /etc/hosts | awk '!/^#/ {print $2}'`
xhost $XHOST_PLUS_LISTE
</pre>
 
xhost gives me:
<pre>
lulu:/home/bav> xhost 
access control enabled, only authorized clients can connect
INET:cola
INET:coca
INET:beta-sw
INET:alfa-sw
INET:bebe
INET:abba
</pre>

<p>

<a href="#toc">Back to Table of Contents</a>

<h2><a name="dns">Remarks concerning DNS</h2>

<I>Netenv</I> does <b>no</b> DNS configuration. Unfortunately there
are a couple of differences in this area looking at the distributions.
<p>
I always felt the mechanism, which David Hinds implemented in his
PCMCIA-package, being sufficient (Script network). This snippet
shows what is happening there:

<pre>
        # Update DNS stuff
        cp /etc/resolv.conf /etc/resolv.new
        echo "# $DEVICE begin" >> /etc/resolv.new
        test "$DOMAIN" && echo "domain $DOMAIN" >> /etc/resolv.new
        if [ "$DNSSRVS $DNS_1 $DNS_2 $DNS_3" != "   " ] ; then
            for DNS in $DNSSRVS $DNS_1 $DNS_2 $DNS_3 ; do
                echo "nameserver $DNS" >> /etc/resolv.new
            done
        fi
        echo "# $DEVICE end" >> /etc/resolv.new
        mv /etc/resolv.new /etc/resolv.conf
</pre>

The file <kbd>/etc/resolv.conf</kbd> is copied to a temporary file. If
one of the variables <kbd>DOMAIN, DNSSRVS, DNS_1,
DNS_2</kbd> or <kbd>DNS_3</kbd> are defined, appropiate commands are
issued. This new section starts e.g. with <kbd># eth0 begin</kbd> and
ends with e.g <kbd># eth0 end</kbd>. These makes are used, to clear
the section, when PCMCIA is shut down. Afterwards
<kbd>/etc/resolv.conf</kbd> will be in the original state.
<p>
So defining e.g. DNS_1 makes this thing work.
<p>
If you want to use <i>netenv</i> for this task, you may put following code
in /etc/netenv/netenv_setup:

<pre>
if [ ! -z "$DNS_1" ]; then 
    (
    echo "# resolv.conf autogenerated by netenv "`date`
    if [ ! -z "$DOMAIN" ]; then echo domain $DOMAIN; fi
    if [ ! -z "$SEARCH" ]; then echo search $SEARCH; fi
    echo nameserver $DNS_1
    if [ ! -z "$DNS_2" ]; then echo nameserver $DNS_2; fi
    ) > /etc/resolv.conf
    chmod 644 /etc/resolv.conf
    echo netenv: /etc/resolv.conf was set up ...
fi
</pre>

<p>

<a href="#toc">Back to Table of Contents</a>

<h2><a name="suse">Remarks for SuSe 7.3 Users</h2>

If you have an  onboard-NIC (so that there is no need to use a
PCMCIA-NIC), you have to override the standard entry  in /etc/rc.config.
You can do this by setting IFCONFIG_0:
<pre>
IFCONFIG_0="172.25.64.130 broadcast 172.25.64.255 netmask 255.255.255.0 up"
</pre>
If you want to use DHCP, the entry must read
<pre>
IFCONFIG_0="dhcpclient"
</pre>

Using netenv you may do this as follows:
    <p>
At first the appropriate profile:

<pre>
elli:/etc/netenv> cat elli-ht
# Networkenvironment: DHCP
export USE_DHCP=yes
NETENV_SCRIPT=/etc/netenv/netenv_setup
</pre>

Furthermore you need a netenv_setup script with at least following
contents: 

<pre>
elli:/etc/netenv> cat netenv_setup
edit_rc_config()
{
   if [ ! -r /etc/rc.config ]; then
      echo No /etc/rc.config, probably not a SuSE-System, giving up ...
      return 1
   fi
   VARIABLE_TO_CHANGE=$1
   shift
   echo ${VARIABLE_TO_CHANGE}'="'$*'"' > /tmp/.netenv.tmp.$$
   LINE=`awk '/^'$VARIABLE_TO_CHANGE'=/ {LINE=NR} END {print LINE}' /etc/rc.config`
   awk -v LINE=$LINE 'NR /tmp/.rc.config.netenv
   cat /tmp/.netenv.tmp.$$ >> /tmp/.rc.config.netenv
   awk -v LINE=$LINE 'NR>LINE' /etc/rc.config >> /tmp/.rc.config.netenv
   cat /tmp/.rc.config.netenv > /etc/rc.config
   rm -f /tmp/.rc.config.netenv /tmp/.netenv.tmp.$$
   echo netenv_setup: rc.config edited, Variable $VARIABLE_TO_CHANGE set to $*
}
if [ "$USE_DHCP" = yes ]; then
   edit_rc_config IFCONFIG_0 dhcpclient
else
   edit_rc_config IFCONFIG_0 "$IPADDR broadcast $BROADCAST netmask $NETMASK up"
fi
</pre>

<p>
SuSe uses the files /etc/route.conf for describing static routing. The
default-route looks like this:
<pre>
default                 172.246.2.1
</pre>
Using the example where netenv edits /etc/hosts you may use e.g.:

<pre>
if grep SuSE /etc/issue 1>/dev/null; then
   if [ ! -z "$GATEWAY" ]; then
    (
    echo "# route.conf autogenerated by netenv "`date`
    echo default $GATEWAY 0.0.0.0 eth0
    ) > /etc/route.conf
    echo netenv_setup: /etc/route.conf was modified ...
   fi
fi
</pre>

<a href="#toc">Back to Table of Contents</a>


<h2><a name="alternatives"><i>netenv</i> Alternatives</h2>

As frequently in Linux there are other choices. Read
<a href="http://tuxmobil.org/Mobile-Guide.db/Mobile-Guide.html">Linux on the
Road - A Guide for Laptops and Mobile Devices</a> by Werner Heuser to
find alternative solutions.
<p>
Those I had a closer look at, try to find out the network environment by
sending arp requests. SuSe recently came up with System Configuration
Profile Management scpm, which is quite powerful but lacks an user
interface during boot which I feel to be important.
<p>

<a href="#toc">Back to Table of Contents</a>

<h2><a name="final">Conclusion</h2>

I hope <i>netenv</i> will be useful for you. Do not hesitate to send
questions and comments to <a href="mailto:bav@epost.de">bav@epost.de</a>. 
<p>

<a href="#toc">Back to Table of Contents</a>

      <hr>
      <address><a href="mailto:bav@epost.de">Gerd Bavendiek</a></address>
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