diff --git a/labs/config/deploy.osbash b/labs/config/deploy.osbash
index 36faf128..c5a2754b 100644
--- a/labs/config/deploy.osbash
+++ b/labs/config/deploy.osbash
@@ -14,4 +14,7 @@
 # Note: shell user name and password are set in preseed.cfg
 VM_SHELL_USER=osbash
 
+# Override disk size in MB (default is 8000 MB, inherited by node VMs)
+# BASE_DISK_SIZE=8000
+
 # vim: set ai ts=4 sw=4 et ft=sh:
diff --git a/labs/lib/osbash/virtualbox.install_base b/labs/lib/osbash/virtualbox.install_base
index 5dd3a535..5c5a7d06 100644
--- a/labs/lib/osbash/virtualbox.install_base
+++ b/labs/lib/osbash/virtualbox.install_base
@@ -42,7 +42,7 @@ function vm_install_base {
     ${WBATCH:-:} vm_attach_guestadd-iso "$vm_name"
 
     ${OSBASH:-:} mkdir -pv "$DISK_DIR"
-    create_vdi "$base_build_disk" 8000
+    create_vdi "$base_build_disk" "${BASE_DISK_SIZE:=8000}"
     vm_attach_disk "$vm_name" "$base_build_disk"
 
     #---------------------------------------------------------------------------