diff --git a/stand/defaults/loader.conf b/stand/defaults/loader.conf
--- a/stand/defaults/loader.conf
+++ b/stand/defaults/loader.conf
@@ -163,6 +163,8 @@
 #kern.ipc.nsfbufs=""		# Set the number of sendfile(2) bufs
 #net.inet.tcp.tcbhashsize=""	# Set the value of TCBHASHSIZE
 #vfs.root.mountfrom=""		# Specify root partition
+#vfs.mountroot.onfallback="ask"	# Action to take if no root found:
+				# "ask" (mountroot prompt), "reboot"
 #vm.kmem_size=""		# Sets the size of kernel memory (bytes)
 #debug.kdb.break_to_debugger="0" # Allow console to break into debugger.
 #debug.ktr.cpumask="0xf"	# Bitmask of CPUs to enable KTR on
diff --git a/sys/kern/vfs_mountroot.c b/sys/kern/vfs_mountroot.c
--- a/sys/kern/vfs_mountroot.c
+++ b/sys/kern/vfs_mountroot.c
@@ -937,8 +937,13 @@
 	if (!(boothowto & RB_DFLTROOT))
 		sbuf_printf(sb, "%s\n", ROOTDEVNAME);
 #endif
-	if (!(boothowto & RB_ASKNAME))
+	s = kern_getenv("vfs.mountroot.onfallback");
+	if (s != NULL) {
+		sbuf_printf(sb, ".%s\n", s);
+		freeenv(s);
+	} else if (!(boothowto & RB_ASKNAME)) {
 		sbuf_printf(sb, ".ask\n");
+	}
 }
 
 static int