diff --git a/release/tools/arm.subr b/release/tools/arm.subr
--- a/release/tools/arm.subr
+++ b/release/tools/arm.subr
@@ -67,22 +67,25 @@
 
 	# Create the target raw file and temporary work directory.
 	chroot ${CHROOTDIR} gpart create -s ${PART_SCHEME} ${mddev}
+
+	arm_create_partitions
+
 	if [ "${PART_SCHEME}" = "GPT" ]; then
 		chroot ${CHROOTDIR} gpart add -t efi -l efi -a 512k -s ${FAT_SIZE} ${mddev}
-		chroot ${CHROOTDIR} newfs_msdos -L efi -F ${FAT_TYPE} /dev/${mddev}p1
 		chroot ${CHROOTDIR} gpart add -t freebsd-ufs -l rootfs -a 64k ${mddev}
-		chroot ${CHROOTDIR} newfs -U -L rootfs /dev/${mddev}p2
 	fi
 	if [ "${PART_SCHEME}" = "MBR" ]; then
 		chroot ${CHROOTDIR} gpart add -t '!12' -a 512k -s ${FAT_SIZE} ${mddev}
 		chroot ${CHROOTDIR} gpart set -a active -i 1 ${mddev}
-		chroot ${CHROOTDIR} newfs_msdos -L efi -F ${FAT_TYPE} /dev/${mddev}s1
 		chroot ${CHROOTDIR} gpart add -t freebsd ${mddev}
-		chroot ${CHROOTDIR} gpart create -s bsd ${mddev}s2
-		chroot ${CHROOTDIR} gpart add -t freebsd-ufs -a 64k -b 64k ${mddev}s2
-		chroot ${CHROOTDIR} newfs -U -L rootfs /dev/${mddev}s2a
+		chroot ${CHROOTDIR} gpart create -s bsd ${mddev}${BSDLABEL_SUFFIX}
+		chroot ${CHROOTDIR} gpart add -t freebsd-ufs -a 64k -b 64k ${mddev}${BSDLABEL_SUFFIX}
 	fi
 
+	# Create the EFI and UFS filesystems
+	chroot ${CHROOTDIR} newfs_msdos -L efi -F ${FAT_TYPE} /dev/${mddev}${EFIPART_SUFFIX}
+	chroot ${CHROOTDIR} newfs -U -L rootfs /dev/${mddev}${ROOTFSPART_SUFFIX}
+
 	return 0
 }
 
@@ -171,12 +174,7 @@
 }
 
 arm_install_base() {
-	if [ "${PART_SCHEME}" = "GPT" ]; then
-		chroot ${CHROOTDIR} mount /dev/${mddev}p2 ${DESTDIR}
-	fi
-	if [ "${PART_SCHEME}" = "MBR" ]; then
-		chroot ${CHROOTDIR} mount /dev/${mddev}s2a ${DESTDIR}
-	fi
+	chroot ${CHROOTDIR} mount /dev/${mddev}${ROOTFSPART_SUFFIX} ${DESTDIR}
 	_OSVERSION=$(chroot ${CHROOTDIR} /usr/bin/uname -U)
 	REVISION=$(chroot ${CHROOTDIR} make -C /usr/src/release -V REVISION)
 	BRANCH=$(chroot ${CHROOTDIR} make -C /usr/src/release -V BRANCH)
@@ -230,14 +228,8 @@
 	FATMOUNT="${DESTDIR%${KERNEL}}/fat"
 	UFSMOUNT="${DESTDIR%${KERNEL}}/ufs"
 	chroot ${CHROOTDIR} mkdir -p "${FATMOUNT}" "${UFSMOUNT}"
-	if [ "${PART_SCHEME}" = "GPT" ]; then
-		dospart="/dev/${mddev}p1"
-		ufspart="/dev/${mddev}p2"
-	fi
-	if [ "${PART_SCHEME}" = "MBR" ]; then
-		dospart="/dev/${mddev}s1"
-		ufspart="/dev/${mddev}s2a"
-	fi
+	dospart="/dev/${mddev}${EFIPART_SUFFIX}"
+	ufspart="/dev/${mddev}${ROOTFSPART_SUFFIX}"
 
 	chroot ${CHROOTDIR} mount_msdosfs ${dospart} ${FATMOUNT}
 	chroot ${CHROOTDIR} mount ${ufspart} ${UFSMOUNT}
@@ -271,3 +263,20 @@
 arm_do_quirk() {
 	# Override in the ${EMBEDDED_TARGET}/${BOARDNAME}.conf file.
 }
+
+arm_create_partitions() {
+	# Override in the ${EMBEDDED_TARGET}/${BOARDNAME}.conf file.
+
+	# Set defaults for EFIPART_SUFFIX, ROOTFSPART_SUFFIX, and
+	# BSDLABEL_SUFFIX (MBR only), needed elsewhere.
+
+	if [ "${PART_SCHEME}" = "GPT" ]; then
+		export EFIPART_SUFFIX=p1
+		export ROOTFSPART_SUFFIX=p2
+	fi
+	if [ "${PART_SCHEME}" = "MBR" ]; then
+		export EFIPART_SUFFIX=s1
+		export BSDLABEL_SUFFIX=s2
+		export ROOTFSPART_SUFFIX=s2a
+	fi
+}