give hints of what to do when failing to find isoinfo

diff --git a/di-maker b/di-maker
index 86b34b2047d5ff8c34ee590d2adc186c0c6d773e..6fa862ff49c7d592bc489b07885952180ae7f140 100755 (executable)
--- a/di-maker
+++ b/di-maker
@@ -76,6 +76,10 @@ esac
 if ! [ -e "$output" ] ; then
     ( cd "$WORKDIR" && wget "$BASEPATH"/{$KERNEL,$INITRAMFS} )
 else
+    if ! which isoinfo > /dev/null; then
+        printf "Could not find isoinfo.\nYou probably need to install the genisoimage\npackage if you want to work with an existing .iso like '%s'.\n" "$output" >&2
+        exit 1
+    fi
     isoinfo -R -i "$output" -x "/$KERNEL" > "$WORKDIR/$KERNEL"
     isoinfo -R -i "$output" -x "/$INITRAMFS" > "$WORKDIR/$INITRAMFS"
 fi