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Do you use your laptop in different network environments ?

If yes, the small package netenv 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.

Netenv 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.

Have a look at netenv's chooser box:

Besides the basic functionality of configuring the NIC, the netenv data can be used for thinks like:

• Choose a proper XF86Config

  Think of using your laptop standalone with touchpad vs. connected to a CRT monitor along with an external wheel mouse.

• Setting up DNS

  You create the appropriate /etc/resolv.conf.

• Printing Environment

  Assigning a proper value for e.g. PRINTER defines a default printer.

• Editing your Netscape preferences file

  So it's possible to avoid network timeouts, when working not connected to the net and viewing only local files.

• Configuring Fetchmail

  Having a permanent connection to my mailserver I use netenv to call fetchmail as a daemon which fetches mail periodically.

• Linking /dev/pilot

  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.

Netenv is available prepackaged for Debian and Redhat Linux as well as tarball. Mandrake- and SuSe-Users may use the RedHat-RPM. netenv depends on dialog(1) resp. gdialog (which comes with the mentionend distributions).

A word to all gurus: In this docu I try to explain things with Linux novices in mind, so be patient.

Table of Contents

What does netenv do ?

Where to get netenv ?

How to install

Basics

First time configuration

Configuration

Examples

Remarks at DNS

Remarks for SuSe 7.3 Users

Remarks for Debian Users

netenv alternatives

Conclusion

Where to get netenv ?

But you may know this already ...

You will find there the tar-file as well as the RedHat-RPM. The latter should be useable in Mandrake and Suse too.

Debian-User

Netenv has been available for Debian quite a while. Look at http://www.debian.org/distrib/packages.

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How to Install

rpm -i netenv-0.94-1.i386.rpm

dpkg -i netenv-0.92-2.i386.deb

apt-get install netenv

tar xvf netenv-0.94-2.tar

The netenv-RPM has been packaged under RedHat 6.1. So it should be possible to install in all distributions using RPM.

The postinstall-script puts

• a call to netenv in /etc/rc.d/rc.sysinit
• and cares for the integration in the NIC's configuration

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

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

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

SuSe

SuSe 8.1

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

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

/etc/sysconfig/network/ifcfg-eth0

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

STARTMODE='onboot'

STARTMODE='hotplug'

SuSe 7.3

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

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

mweb@guru:/etc/rc.d > head -16 network 
#! /bin/sh
# Copyright (c) 1996 SuSE GmbH Nuernberg, Germany.  All rights reserved.
#
# Author: Florian La Roche , 1996
#       Werner Fink , 1996
#       Burchard Steinbild , 1996
#       Rolf Haberrecker , 1998
#       Werner Fink  (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

Debian

Mandrake

How to use the tar-file

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

netenv must be called before the normal network- or PCMCIA-start. Check for /etc/init.d/boot.local or the equivalent. See the SuSE 8.1 paragraph for further details.

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 ifup to start a preconfigured net interface. Then the SuSE 8.1 paragraph should contain the details.

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 dmesg | grep eth and lspci.

Netenv checks for eth1, but depending on the configuration at the time of installation this cannot be waterproof.

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Basics

linux NETENV=office

After having selected the current environment, netenv copies the actual file to /tmp/netenv[1].

This file has modes 644, so being readable by any user for further user dependent configuration tasks.

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First time configuration

netenv

    new  Set_up_new_environment  

   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 ...  

BOOTPROTO='dhcp'
STARTMODE='hotplug'

STARTMODE='onboot'

Finally you will be asked if you want to save this configuration for further use:

    Do you want to save this configuration ?

Depending on the Distribution netenv offers to restart the network and to activate the changes this way.

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

/etc/init.d/pcmcia restart

Ping your gateway-address and you will know !

Didn't work ? Is the link-LED green ? Check the output of

ifconfig eth0

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 ...

Those, who use a NIC onboard instead of a PCMCIA-NIC have to restart their network.

In RedHat or SuSE e.g.:

/etc/init.d/network restart

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Configuration

/etc/netenv/<NODE-NAME>-<VALUE-OF-VARIABLE-NETENV>

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

netenv_id=At_Home_LCD_WheelMouse_pcmcia
...
IPADDR=123.456.78.9
...
NETSCAPE_PROXY_TYPE=2

IPADDR
NETMASK
NETWORK
BROADCAST

GATEWAY
DNS_1

NETENV_SCRIPT=/etc/netenv/netenv_setup

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 !

With the help of this script you may do quite useful things. More on this in the example section.

Expert Mode

This is a security risk! Anybody with physical access to your computer will get a root shell without having to enter a password!

Therefore this feature is diabled in Debian, unless you set ALLOW_EXPERT to "YES" in netenv.conf (see below).

Security hints:

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Examples

The examples are described step by step. So please read them one after the other !

StandAlone_Touchpad

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

The value of the variable netenv_id (as I said earlier: Please without spaces) will be used as decription in the chooser box.

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 here.

This sample is written in a simple manner to get you started. Relevant code section here is:

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
...

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:

In my private configuration I use NETSCAPE_PROXY_TYPE:

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
...

In_the_Office

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

PRINTER=cc_hp sets the defaultprinter to the printer in the office. NETSCAPE_PROXY_TYPE=2 activates automatic proxyconfiguration in Netscape.

When I am in the office, mail shall be fetched periodically. For this I use FETCHMAIL_POLL_INTERVALL. The following snippet from my ~/.xinitrc starts fetchmail as daemon, which will became active every 15 min and carry out things defined in ~/.fetchmailrc:

if [ -n "$FETCHMAIL_POLL_INTERVALL" ]; then 
   fetchmail -d $FETCHMAIL_POLL_INTERVALL
fi

Laptop_at_home

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'

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
...

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.

At home my laptop is in a docking-unit. This has a NIC. In order to use this NIC

STARTMODE='onboot'

At_Customer_Foobar

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.

I put marks in my /etc/hosts like this:

lulu:/home/bav> cat /etc/hosts
...
# netenv hosts begin
# netenv hosts end
...

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"

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

...
# 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
...

XHOST_PLUS_LISTE=`awk '/^# netenv hosts begin$/,/^# netenv hosts end$/' /etc/hosts | awk '!/^#/ {print $2}'`
xhost $XHOST_PLUS_LISTE

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

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Remarks concerning DNS

        # 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

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

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Remarks for SuSe 7.3 Users

IFCONFIG_0="172.25.64.130 broadcast 172.25.64.255 netmask 255.255.255.0 up"

IFCONFIG_0="dhcpclient"

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

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

default                 172.246.2.1

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

Remarks for Debian Users

Overview

• configuration in /etc/network/interfaces
• configuration in /etc/pcmcia/network.opts

Additional features with Debian

netenv and the offline-http-proxy wwwoffle

Installation and configuration in Debian

Upon installation of the Debian package it tries to set up a network configuration that corresponds to your current settings. Unfortunately, network setup is done quite differently in Debian, compared to other distributions. Additionally, there are two possibilities for the network setup. Therefore you have to do some things manually, either for installation or when you want to create new network configurations.

If netenv cannot parse the current configuration, it will not be called upon boot, and the computer will behave as it was before the installation. In this case you have to set up a working configuration as described below and then create the necessary startup link to the init-script with the command

update-rc.d netenv start 40 S

The following paragraphs describe which user changes are required: If the network settings are stored in /etc/network/interfaces so far, then netenv will work at once - however creating a new configuration for the network chooser box is somewhat complicated. In Debian, this method is in use with built-in network cards ("on-board") and sometimes with PCMCIA-cards. The second method, where the network settings are in /etc/pcmcia/network.opts, can only be used with PCMCIA-cards.

The installation routine detects which method is used and sets up a sample configuration accordingly. With both methods, however, the user has to make some changes to make things work! If network settings are found in both files - or in none of them -, no configuration is generated so far, and netenv is not called upon booting. The same will happen if it found network settings in /etc/network/interfaces, but this file is yet a symbolic link (see below).

configuration in /etc/network/interfaces

The syntax of interfaces is fundamentally different compared to netenv's expectations - i.e. no variable assignments are used. Consequently there is no possibility to simply "supersede" the information from this file. Instead, netenv is instructed to execute a script after you chose a network environment. This script redirects symbolic links. The outcome looks like the following:

ls -l /etc/network/interfaces*
 /etc/network/interfaces -> /etc/network/interfaces.work
 /etc/network/interfaces.home
 /etc/network/interfaces.work
 /etc/network/interfaces.offline
 /etc/network/interfaces.old -> /etc/network/interfaces.offline

This means that no files are changed, it is only the symbolic link /etc/network/interfaces which is redirected to the appropriate target. The file /etc/resolv.conf must be treated in the same way. Note that for offline use, you need to set up a lo device in interfaces.

The commands that redirect these links could, in principle, be put directly in the configuration files for the respective network environment. On a computer named lulu they would, e.g., be in /etc/netenv/lulu-home, /etc/netenv/lulu-office etc. However, the author of netenv recommends to keep only variable assignments in these files. Specifically, one can define the variable NETENV_SCRIPT. This script is then automatically executed and makes the desired links.

An example configuration on machine lulu could look like this: In /etc/netenv/ we have the following files:

lulu        lulu-customer  lulu-offline      setup-customer      setup-offline
lulu-work   lulu-home      netenv.conf       setup-work          setup-home

netenv_id=Arbeit
export NETENV_SCRIPT=/etc/netenv/setup-work

# you can set any variable here. export it!

The variable netenv_id is used in the chooser dialog box of netenv, the script setup-work is executed (sourced, to be exact) after lulu-work has been read. It looks like this:

#!/bin/sh

if [ -r /etc/network/interfaces.work ]; then
  mv /etc/network/interfaces /etc/network/interfaces.old
  ln -s /etc/network/interfaces.work /etc/network/interfaces
fi
if [ -r /etc/resolv.conf.work ]; then
  mv /etc/resolv.conf /etc/resolv.conf.old
  ln -s /etc/resolv.conf.work /etc/resolv.conf
fi
if [ -r /etc/exim/exim.conf.work ]; then
  mv /etc/exim/exim.conf /etc/exim/exim.conf.old
  ln -s /etc/exim/exim.conf.work /etc/exim/exim.conf
fi

As you can see, also other files can handily be customized like this. Once a configuration is set up - which is usually done by the package setup - it should be easy to add more of them.

However, you cannot use the menu option "new" in the chooser box of netenv to create a new configuration. This is because it will only write variable assignments into a new lulu-file, but not create the necessary script. Instead, you have to manually create and and edit files in /etc/netenv/ with contents analogous to the files described above: $computername-$networkname defines the NETENV_SCRIPT, which in turn redirects the symbolic links. The Debian setup will create these files with the names $computername (configuration file) and setup-default (NETENV_SCRIPT), respectively.

alternatives for /etc/network/interfaces

There are even more possibilities to configure netnev if the network settings are stored in /etc/network/interfaces. Especially the "mapping" mechanism, as described in the manpage interfaces(5) is very interesting. An other way is outlined in the file netenv_setup_debian_example.

configuration in /etc/pcmcia/network.opts

If your network settings are stored in /etc/pcmcia/network.opts, you have one big advantage: This file uses variable assignments, for example

IPADDR="123.456.789.12"

This is exactly the method that netenv was originally built for. Consequently, you can simply use the menu option "new" (Set_up_new_environment) in its chooser dialog box to create a new network environment.

However, in order that these variables are in effect when a network card ist started, they need to be read in in /etc/pcmcia/network.opts. Since this file belongs to the package pcmcia-cs, netenv is not allowed to change it during setup. However, you as a user (or rather administrator) may and should do it. The simplest way would be to add the line

. /var/tmp/netenv

to the end of the file (yes, with the leading dot!). Somewhat more sophisticated would be to apply the following patch (also included as netenv-network.opts.patch):

--- etc/network.opts.orig	Sat Nov  8 12:10:56 2003
+++ etc/network.opts	Sat Nov  8 12:42:27 2003
@@ -21,6 +21,8 @@
     PPPOE="n"
     # Use WHEREAMI (via the whereami package)? [y/n]
     WHEREAMI="n"
+    # Use NETENV (via the netenv package)? [y/n]
+    USE_NETENV="y"
     # Host's IP address, netmask, network address, broadcast address
     IPADDR=""
     NETMASK="255.255.255.0"
@@ -55,5 +57,13 @@
     # Card eject policy options
     NO_CHECK=n
     NO_FUSER=n
+    if [ $USE_NETENV = y ]; then
+      if [ -r /var/tmp/netenv ]; then
+	. /var/tmp/netenv
+      else
+	echo "/var/tmp/netenv unreadable. Perhaps you should set"
+	echo "USE_NETENV=n in /etc/pcmcia/network.opts"
+      fi
+    fi
     ;;
 esac

This has several effects. First, it allows for easy deactivation of netenv. Second, the first pair of lines is added near the place where also wherami, a program with similar functionality, is configured - anybody will easily find out that netenv is used. This might be interesting in case of a bug report. Third and last there is an additional check for existence and readability of the file where netenv stores the information to be used this time.

Additional features with Debian

expert mode

The expert mode is a security risk, because it means to get a root-shell without entering a password. Therefore it is disabled in Debian. If you want to use it anyway, use the following variable assignment in netenv.conf:

ALLOW_EXPERT=YES

You have been warned!

Automatic selection of a default configuration

Debian's dialog Program (not gdialog from the gnome-utils package, which otherwise works fine with netenv) has a timeout function. If you set the variable NETENV_TIMEOUT to an integer larger than 0, the dialog during boot will wait as many seconds. If no input is detected during that interval, the default configuration will be booted, i.e. the file in /etc/netenv/ which has the same name as the hostname will be used. If NETENV_TIMEOUT is set to zero, then it will not timeout and wait for an input. Beware that the latter behavior will break remote boots!

Remembering last selection.

Debian's netenv can also remember your last selection. You can enable this by setting the NETENV_REMEMBER_LAST variable to yes. Furthemore if you set it to default, in case of timeout your last selection will be used instead of the normal default (see above).

Selection of the default configuration using a variable

The default configuration for netenv corresponds to the file /etc/netenv/$hostname (without a trailing "-place"). You can normally bypass the selection dialog by setting the variable NETENV to the name of the place, either as an argument to the kernel loader, or as an environment variable during normal system operation. This is, however, not possible for the default, since this would mean an empty NETENV variable. In Debian, you can use the hostname instead: On a computer named lulu

NETENV=someplace netenv

will change to the setup specified in /etc/netenv/lulu-someplace, whereas

NETENV=lulu netenv

will bring you to /etc/netenv/lulu.

Automatic restart of daemons

Starting from 0.94 of netenv it is possible to call the program during normal system operation and change the network configuration. Some background processes (daemons) may have to be restarted or made to reread there config files (which may have changed, see below). All init scripts that are assigned to NETENV_RUN_INIT_SCRIPTS in the configuration file are executed with the parameter restart after changing the network configuration. The scripts are specified as a space separated list, enclosed in quotes, e.g.

NETENV_RUN_INIT_SCRIPTS="chrony myinitscript"

/etc/init.d/networking will be executed in any case.

Bypassing the "restart networking now?" dialog

Before doing the automatic daemon restarting as described above, netenv will ask whether to restart the network at all (when called during normal system operation). This can be bypassed by setting the variable NETENV_DO_RESTART in netenv.conf to yes (meaning to always restart without asking) or never (meaning to never restart).

netenv and the offline-http-proxy wwwoffle

As described above it is possible to tell netenv to restart some daemons using their init scripts. Unfortunately this does not work with wwwoffle. The reason is that wwwoffle remembers its status (online or offline) before stopping the service, and restores it after starting again. This is reasonable under some circumstances (e.g. if the wwwoffle package is updated while being online). However, it has the unwanted result that

/etc/init.d/wwwoffle restart

Therefore there is an other variable for wwwoffle (and possibly other scripts with similar behavior), NETENV_START_STOP_SCRIPTS. Scripts in this space-separated list will not be called with restart, instead first with stop and afterwards with start.

The Debian maintainer of netenv thinks this behavior of the wwwoffle package is a bug, see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=224937.

netenv Alternatives

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.

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Conclusion

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Footnotes