Switching from DHCP to Static IP

Applications IP Networking
1

I am trying to write a set of scripts for my Ubuntu 810 Server to allow a user to change from DHCP to a user-supplied Static IP, Subnet, Gateway and DNS Servers.

So far I have the following, where $USERCHOICE is a user-entered value in each case:
ifconfig eth0 down && ifconfig eth0 $USERCHOICE && ifconfig eth0 up;;
ifconfig eth0 down && ifconfig netmask $USERCHOICE && ifconfig eth0 up;;
ifconfig eth0 down && route add default gw $USERCHOICE && ifconfig eth0 up;;
ifconfig eth0 down && echo "nameserver $USERCHOICE" > /etc/resolv.conf && ifconfig eth0 up;;

Problems:
1.It doesn't work :), even after issuing /etc/init.d/networking restart
2. Is there an easy way to, from a script, take multiple values and run each command using the appropriate value rather than running each component as a different option?
3. How do I specify 2 DNS Servers instead of 1?

I suspect someone out there is already doing this, and in a much more straightforward fashion that I am attempting to

Thanks for any help.

Alex

2

The following code of mine (quoted in extracts) has been used to allow for updating the network settings of a Debian-based live system at boot time ...:

  eth0|eth1)

    updateConsole

    echo -ne "\e[33m"
    echo ""
    echo "          \|||/                          "
    echo "          (0 0)                          "
    echo "-------ooO-(_)-Ooo-----------------------"
    echo ""
    echo "Attempting to upset, er, setup <$OPTION> ..."
    echo ""

    ADDRESS="192.168.110.100"
    echo -n "Address [192.168.110.100]: "
    read address
    if [ "$address" != "" ]
    then
      ADDRESS="$address"
    fi
    GATEWAY="192.168.110.101"
    echo -n "Gateway [192.168.110.101]: "
    read gateway
    if [ "$gateway" != "" ]
    then
      GATEWAY="$gateway"
    fi
    echo ""
    echo -ne "\e[0m"

    ETH=/etc/network/interfaces
    mv $ETH $ETH.dhcp

    ifconfig lo 127.0.0.1
    route add 127.0.0.0 lo

    ifconfig "$OPTION" "$ADDRESS" netmask 255.255.255.0
    route add "$ADDRESS" "$OPTION"

    route add default gw "$GATEWAY" "$OPTION" > /dev/null 2>&1

    DNS=/etc/resolv.conf
    mv $DNS $DNS.dhcp && touch $DNS
    echo "nameserver 208.67.220.220" >> $DNS
    echo "nameserver 208.67.222.222" >> $DNS

    ping -c 1 housisms.net > /dev/null 2>&1
    if [ $? -eq 0 ]
    then
      echo -ne "\e[32m"
      echo "You're now part of the 'World Wide Wait'."
      SAVE="yes"
    else
      echo -ne "\e[31m"
      echo "Nice try - to no avail, I'm (not) afraid."
      SAVE="no"
    fi
    echo ""
    echo -ne "\e[0m"
    
    if [ "$SAVE" = "yes" ]
    then
    
      BROADCAST="`echo $ADDRESS | awk -F '.' '{ print $1"."$2"."$3".255"}'`"
    
      touch $ETH
      echo "auto lo" >> $ETH
      echo "iface lo inet loopback" >> $ETH
      echo "auto $OPTION" >> $ETH
      echo "iface $OPTION inet static" >> $ETH
      echo "address $ADDRESS" >> $ETH
      echo "netmask 255.255.255.0" >> $ETH
      echo "broadcast $BROADCAST" >> $ETH
      echo "gateway $GATEWAY" >> $ETH
    fi

  ;;