Remove your old kernels on SUSE

rmOldKernels.sh

#!/bin/bash
UNAME=$(uname -r)
CUR_array=($(echo "$UNAME" | awk -F'[.-]' '{print $1 "\n" $2 "\n" $3 "\n" $4}'))
CUR=$(echo ${CUR_array[@]} | tr -d ' ')
FOUND=0

function compare {
    for J in {0..3}; do
        if (( "${THIS_array[J]}" > "${CUR_array[J]}" )); then break
        elif (( "${THIS_array[J]}" < "${CUR_array[J]}" )); then
            LIST+=($I)
            FOUND=1
            break
        fi
    done
}

for I in $(rpm -q kernel-default); do
    THIS_array=($(echo "$I" | awk -F'[.-]' '{print $3 "\n" $4 "\n" $5 "\n" $6}'))
    THIS=$(echo ${THIS_array[@]} | tr -d ' ')

    if [[ "${THIS}" == "${CUR}" ]]; then continue
    else compare
    fi
done

if ((FOUND)); then
    echo "Currently running kernel-$UNAME"
    zypper remove "${LIST[@]}"
fi