Preserve ubuntu-advantage-tools' apt preferences against live-build's attempt to delete them.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.208.18) UNRELEASED; urgency=medium
+
+  * Preserve ubuntu-advantage-tools' apt preferences against live-build's
+    attempt to delete them.
+
+ -- Michael Hudson-Doyle <michael.hudson@ubuntu.com>  Fri, 06 Dec 2019 10:23:03 +1300
+
 livecd-rootfs (2.208.17) trusty; urgency=medium
 
   * Drop /etc/update-motd.d/51-cloudguest from cloud images; this is not

live-build/auto/build

@@ -49,6 +49,12 @@ EOF
 
 	lb chroot "$@"
 
+	if [ -d chroot/etc/apt/preferences.d.save ]; then
+		# https://twitter.com/infinite_scream
+		mv chroot/etc/apt/preferences.d.save/* chroot/etc/apt/preferences.d/
+		rmdir chroot/etc/apt/preferences.d.save
+	fi
+
 	if [ -f config/oem-config-preinstalled ]; then
 
 # This is cargo-culted almost verbatim (with some syntax changes for

live-build/auto/config

@@ -632,6 +632,18 @@ case $PROJECT in
 		cat > config/hooks/100-remove-fstab.chroot <<EOF
 #! /bin/sh
 rm -f /etc/fstab
+EOF
+		;;
+
+	ubuntu-base)
+		cat > config/hooks/100-preserve-ua-tools-prefs.chroot <<EOF
+#! /bin/sh -ex
+
+# live-build "helpfully" removes /etc/apt/preferences.d/* so we put a
+# copy somewhere it won't touch it.
+
+cp -a /etc/apt/preferences.d /etc/apt/preferences.d.save
+
 EOF
 		;;