diff --git a/tools/tools/nanobsd/defaults.sh b/tools/tools/nanobsd/defaults.sh
--- a/tools/tools/nanobsd/defaults.sh
+++ b/tools/tools/nanobsd/defaults.sh
@@ -102,6 +102,7 @@
 
 # Newfs parameters to use
 NANO_NEWFS="-b 4096 -f 512 -i 8192 -U"
+NANO_MAKEFS="-o bsize=4096,density=8192,fsize=512,softupdates=1,version=2"
 
 # The drive name of the media at runtime
 NANO_DRIVE=ada0
@@ -684,6 +685,18 @@
 	mount -o async ${dev} ${mnt}
 )
 
+nano_makefs ( ) {
+	local dir image metalog options size
+	options=$1
+	metalog=$2
+	size=$3
+	image=$4
+	dir=$5
+
+	makefs ${options} -F "${metalog}" -N "${NANO_WORLDDIR}/etc" \
+	    -s "${size}b" -T "${NANO_TIMESTAMP}" -t ffs "${image}" "${dir}"
+}
+
 # Convenient spot to work around any umount issues that your build environment
 # hits by overriding this method.
 nano_umount ( ) (
@@ -998,6 +1011,7 @@
 	export_var NANO_IMGNAME
 	export_var NANO_IMG1NAME
 	export_var NANO_MAKE
+	export_var NANO_MAKEFS
 	export_var NANO_MAKE_CONF_BUILD
 	export_var NANO_MAKE_CONF_INSTALL
 	export_var NANO_MEDIASIZE
diff --git a/tools/tools/nanobsd/legacy.sh b/tools/tools/nanobsd/legacy.sh
--- a/tools/tools/nanobsd/legacy.sh
+++ b/tools/tools/nanobsd/legacy.sh
@@ -93,6 +93,17 @@
 	' > ${NANO_LOG}/_.partitioning
 )
 
+_xxx_adjust_code_size()
+{
+	# XXX adjust the CODE_SIZE value by rounding it up to
+	# a bsize of 32768 (DFL_BLKSIZE).
+	# Otherwise makefs -s will fail because of the guard
+	# introduced in 5ad283b3c60d.
+	codesize=$1
+	bsize=32768
+	echo $(( ((codesize + (bsize - 1)) / bsize) * bsize ))
+}
+
 create_code_slice ( ) (
 	pprint 2 "build code slice"
 	pprint 3 "log: ${NANO_OBJ}/_.cs"