source: debian/postinst @ 136

#!/bin/sh

case "$1" in
    configure)

    # Prepare the sasldb for postfix :
    touch /etc/sasldb
    chgrp 33 /etc/sasldb
    chmod g+w /etc/sasldb

    # Source debconf library.
    . /usr/share/debconf/confmodule
    db_version 2.0
    db_title AlternC
    db_input medium alternc/welcomeconfirm
    db_go

    # Check the answer.
    db_get  alternc/welcomeconfirm
    if [ "$RET" = "false" ]; then
        exit -1
    fi

    db_fset alternc/info seen false
    db_input medium alternc/info
    db_go

    # Now configure the default values for the config file : 
    # only if needed (config file with "exit" on line 1)
    if [ "`head -1 /etc/alternc/alternc.conf`" = "exit" ]
    then
    
        # myip
        # Return the ip of the first found interface on the computer
        myip=`cat /etc/network/interfaces |grep address |grep -v "#" |head -1|sed -e 's/^.*address[^0-9\.]*\([0-9\.]*\)/\1/' `
        # fqdn
        # Return the complete dns name of the computer
        fqdn=`cat /etc/mailname`
        mx=`cat /etc/mailname`
        
        # DATA_PART
        # Return the disk partition where /var/alternc is mounted
        DATA_PART=`mount |grep 'on /var/alternc '|sed -e 's/^\([^ ]*\).*$/\1/' `
        if [ -z "$DATA_PART" ]
            then
            DATA_PART=`mount |grep 'on /var '|sed -e 's/^\([^ ]*\).*$/\1/' `
        fi
        if [ -z "$DATA_PART" ]
            then
            DATA_PART=`mount |grep 'on / '|sed -e 's/^\([^ ]*\).*$/\1/' `
        fi
        
        DATA_PART=`echo "$DATA_PART" | sed -e 's/\//\\\\\//g'`
        # Generate random passwords 
        dbpwd=`perl -e 'print map{("a".."z","A".."Z",0..9)[int(rand(62))]}(1..10)' `
        myrandom=`perl -e 'print map{("a".."z","A".."Z",0..9)[int(rand(62))]}(1..10)' `
        ldap_userpwd=`perl -e 'print map{("a".."z","A".."Z",0..9)[int(rand(62))]}(1..10)' `
        ldap_rootpwd=`perl -e 'print map{("a".."z","A".."Z",0..9)[int(rand(62))]}(1..10)' `
        
        # Now substitute it on the conf file ;) 
        cat /etc/alternc/alternc.conf | sed -e "s/^myip=.*/myip=$myip/" | sed -e "s/^fqdn=.*/fqdn=$fqdn/" | sed -e "s/^mx=.*/mx=$mx/" | sed -e "s/^DATA_PART=.*/DATA_PART=$DATA_PART/" | sed -e "s/^dbpwd=.*/dbpwd=$dbpwd/" | sed -e "s/^myrandom=.*/myrandom=$myrandom/" | sed -e "s/^ldap_userpwd=.*/ldap_userpwd=$ldap_userpwd/" | sed -e "s/^ldap_rootpwd=.*/ldap_rootpwd=$ldap_rootpwd/" >/etc/alternc/alternc.conf.new
        rm /etc/alternc/alternc.conf
        mv /etc/alternc/alternc.conf.new /etc/alternc/alternc.conf
    fi


esac

# dh_installdeb will replace this with shell code automatically
# generated by other debhelper scripts.

#DEBHELPER#

exit 0