Code:
#!/bin/bash
#
# Description
#   Add specified MBs to the size of your knoppix-data.img partition.
#   Haven't tested the LIBEXT=aes version. You are liable if you uncomment
#   the operational lines below. It worked for me.
# Usage
#    sudo ./resizeImg      # add default 100 MB to your current img
#    sudo ./resizeImg 1000 # add 1000 MB (1GB) to your current img
# Author
#    koolb@hotmail.com
#
MYDATA=/mnt/sda2                   # make this an area on any HD

set -e                             # exit on any errors..and do some checking
[ $(id -u) -eq 0 ] || exec echo "You prolly need to be root. You are $(id -nu)"
du | fgrep $(basename $MYDATA) || exec echo "You need to have a $MYDATA mounted"

# review these to see if they need to change for your dist or prefs
ADDMB=${1:-100}                    # append specified/default 100 Megabytes...
PWD=aes-password                   # only set this if LIVEXT=aes
#This should be the same for recent knoppix releases
LIVEXT=img # img or aes            # Active img extension
BUIMG=$MYDATA/knoppix-data.$LIVEXT # BackUp IMaGe
LIVEDIR=/mnt-system/KNOPPIX        # Active img location
LIVEIMG=$LIVEDIR/knoppix-data.$LIVEXT

TMPIMG="$LIVEDIR/$(basename $LIVEIMG .$LIVEXT).bak"
LOOP=$(losetup -f)                 # get an available loop device

echo "Syncing buffers..."
time sync                          # optional flush all data/buffers to disk
echo "Copying live to backup..."
time cp -p $LIVEIMG $MYDATA        # backup/copy
echo "Adding..."
time dd if=/dev/zero bs=1M count=$ADDMB >> $BUIMG
FS=$BUIMG
[ $LIVEXT = aes ] && echo $PWD | losetup -e $LIVEXT -p 0 -s $LOOP $FS && FS=$LOOP
set +e                             # bound to have some fixups from live
echo "Cleaning fs..."
time e2fsck -fy $FS                # clean the backup
set -e                             # resize will force exit on error(s)
echo "Resizing..."
time resize2fs $FS
echo "Checking FS again..."
time e2fsck -y $FS                # clean after resize
[ $LIVEXT = aes ] && losetup -d $LOOP
# ideally do this in a transaction with rollback upon error

echo "Moving into place..."
#mv $LIVEIMG $TMPIMG                # I was able to do this on a live system
#time mv $BUIMG $LIVEIMG            # which is one reason why i love Linux!