/var/vm is a terrible idea, the images are filled on demand, they are

not backed by blocks until used.
So I'll use /home/vm instead.
Pointed out by deraadt@

src/etc/examples/vm.conf

@@ -1,4 +1,4 @@
-# $OpenBSD: vm.conf,v 1.1 2015/12/07 13:58:48 reyk Exp $
+# $OpenBSD: vm.conf,v 1.2 2015/12/07 16:40:41 reyk Exp $
 
 #
 # Macros
@@ -15,7 +15,7 @@ vm "openbsd.vm" {
 	kernel $sets "bsd.rd"
 
 	# First disk from 'vmctl create "/var/vm/OpenBSD.img" -s 4G'
-	disk "/var/vm/OpenBSD.img"
+	disk "/home/vm/OpenBSD.img"
 
 	# Second disk from OpenBSD contains the install sets
 	disk $sets "install58.fs"
@@ -30,5 +30,5 @@ vm "vm1.example.com" {
 	memory 1G
 	interfaces 2
 	kernel "/bsd"
-	disk "/var/vm/vm1-disk.img"
+	disk "/home/vm/vm1-disk.img"
 }