-# Prefix of the GuixSD VM image file name.
-GUIXSD_VM_IMAGE_BASE = guixsd-vm-image-$(PACKAGE_VERSION)
+# Prefix of the Guix VM image file name.
+GUIX_SYSTEM_VM_IMAGE_BASE = guix-system-vm-image-$(PACKAGE_VERSION)
+
+# Flags for 'guix system vm-image'. By default create a VM image that appears
+# to have a 20G hard disk.
+GUIX_SYSTEM_VM_IMAGE_FLAGS ?= --image-size=30G
+
+# Return the sequence of '-s' flags for the given systems.
+system_flags = $(foreach system,$(1),-s $(system))