diff --git a/initramfs/ubuntu/hooks/grub-btrfs-overlay b/initramfs/ubuntu/hooks/grub-btrfs-overlay
index 75d4644..f0676c1 100755
--- a/initramfs/ubuntu/hooks/grub-btrfs-overlay
+++ b/initramfs/ubuntu/hooks/grub-btrfs-overlay
@@ -12,3 +12,4 @@ esac
 
 . /usr/share/initramfs-tools/hook-functions
 manual_add_modules overlay
+copy_exec /usr/bin/findmnt /usr/bin
diff --git a/initramfs/ubuntu/scripts/local-bottom/grub-btrfs-overlay b/initramfs/ubuntu/scripts/local-bottom/grub-btrfs-overlay
index 1481587..3049423 100755
--- a/initramfs/ubuntu/scripts/local-bottom/grub-btrfs-overlay
+++ b/initramfs/ubuntu/scripts/local-bottom/grub-btrfs-overlay
@@ -1,30 +1,32 @@
 #!/bin/sh -e
 PREREQ=
 prereqs() {
-  echo "$PREREQ"
+	echo "$PREREQ"
 }
 case $1 in
-  prereqs)
-    prereqs
-    exit 0
-    ;;
+	prereqs)
+		prereqs
+		exit 0
+		;;
 esac
 
 . /scripts/functions
 on_err() {
-	panic 'script error'
+	log_failure_msg 'error setting up overlay'
 }
 trap on_err ERR
-if [ "$readonly" = y ]
+if [ -x /usr/bin/btrfs -a -x /usr/bin/findmnt ] &&
+		 [ "$(findmnt -no FSTYPE -M "$rootmnt")" = btrfs ] &&
+		 [ "$(btrfs property get $rootmnt ro)" != ro=false ]
 then
-	log_begin_msg 'remount read-only root as read-only layer in non-persistent, writable overlay'
-	lower_dir="$(mktemp -d -p /)"
-	ram_dir="$(mktemp -d -p /)"
+	log_begin_msg 'remount read-only subvolume as read-only layer in non-persistent, writable overlay'
+	trap log_end_msg EXIT
+	lower_dir="$(mktemp -dp /)"
+	ram_dir="$(mktemp -dp /)"
 	upper_dir="$ram_dir"/upper
 	work_dir="$ram_dir"/work
 	mount --move "$rootmnt" "$lower_dir"
 	mount -t tmpfs cowspace "$ram_dir"
 	mkdir -p "$upper_dir" "$work_dir"
 	mount -t overlay -o lowerdir="$lower_dir",upperdir="$upper_dir",workdir="$work_dir" rootfs "$rootmnt"
-	log_end_msg
 fi