--- /etc/grub.d/10_linux.orig	2017-03-24 07:32:33.000000000 +0100
+++ /etc/grub.d/10_linux	2017-05-17 20:38:01.198390372 +0200
@@ -1,5 +1,6 @@
 #! /bin/sh
 set -e
+set -x
 
 # grub-mkconfig helper script.
 # Copyright (C) 2006,2007,2008,2009,2010  Free Software Foundation, Inc.
@@ -78,6 +79,15 @@
 	fi;;
     xzfs)
 	rpool=`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 2>/dev/null || true`
+	# JEL: 
+	# bogus/debian castrated grub isn't able to determine the root poolname
+	# properly because it simply does a 'zpool status' and prefixes all
+	# device basenames with '/dev/'. Therefore /dev/chassis/SYS/HDD0/HDD0p2
+	# and the like let grub explode.
+	if [ "x${rpool}" = "x" ]; then
+		rpool=`df / | awk '{ if ( $6 == "/" ) { split($1,a,"/"); print a[1];}}'`
+		[ "x${rpool}" = "x" ] && rpool='rpool'
+	fi
 	bootfs="`make_system_path_relative_to_its_root / | sed -e "s,@$,,"`"
 	LINUX_ROOT_DEVICE="ZFS=${rpool}${bootfs}"
 	;;