Removing old kernels from Ubuntu

remove_kernels.sh

#!/bin/bash

if [ `id -u` -ne 0 ]; then
    echo "Please run as root"
    exit
else
    kernelsv=`ls /boot | grep vmlinuz | cut -d'-' -f2,3`
    nkernv=0
    out=''
    for kernv in ${kernelsv[@]}
    do
        out="$out FALSE $kernv"
        nkernv=$(( $nkernv + 1 ))
    done
    height=$(( 100 + $nkernv * 30 ))
    remkern=`zenity --list --checklist --separator=" " --height $height  --column "Remove" --column "Kernel version" $out`
    flag=0
    for rmker in ${remkern[@]}
    do
        lista=`dpkg -l | grep ^ii | grep $rmker | awk -F' ' '{ print $2 }'`
        zenity --question --text "Remove this packages?:\n\n$lista"
        if [[ $? = 0 ]]; then
            flag=1
            echo "Removing $rmker"
            lista=`dpkg -l | grep ^ii | grep $rmker | awk -F' ' '{ printf ("%s ", $2) }'`
            apt-get --purge --yes remove $lista
        fi
    done
    if [[ $flag = 1 ]]; then
        update-grub
    fi
fi