The target for x86 ubuntu-core images is VMs, so create them with

a buffer of free space in order to work if booted in place.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.481) UNRELEASED; urgency=medium
+
+  * The target for x86 ubuntu-core images is VMs, so create them with
+    a buffer of free space in order to work if booted in place.
+
+ -- Steve Langasek <steve.langasek@ubuntu.com>  Wed, 08 Nov 2017 12:01:25 -0800
+
 livecd-rootfs (2.480) bionic; urgency=medium
 
   [ Gary Wang ]

live-build/auto/build

@@ -17,8 +17,20 @@ fi
 
 if [ "${IMAGEFORMAT:-}" = "ubuntu-image" ]; then
 	# Use ubuntu-image instead of live-build
+
+	# this should actually be per-model instead of per-architecture,
+	# but for the moment all our x86 models follow this rule.
+	case $ARCH in
+		amd64|i386)
+			extra_args="--image-size 3700M"
+			;;
+		*)
+			extra_args=""
+			;;
+	esac
+
 	env SNAPPY_STORE_NO_CDN=1 \
-	ubuntu-image -c edge \
+	ubuntu-image -c edge $extra_args \
 		-o livecd."$PROJECT".img livecd."$PROJECT".model-assertion
 	xz -0 -T4 livecd."$PROJECT".img
 	exit 0