address review comments

live-build/auto/config

@@ -778,6 +778,12 @@ case $PROJECT in
 					add_package ubuntu-server.installer s390-tools-zkey
 				fi
 
+				# Live server ISOs for LTS point releases past .2 offer both
+				# the GA and HWE kernels (in separate layers) so this code is
+				# written generically to support both even though a lot of the
+				# time only one kernel is offered.
+
+				# variants='ga hwe'
 				variants='ga'
 
 				for variant in $variants; do
@@ -797,7 +803,7 @@ case $PROJECT in
 				done
 				;;
 			*)
-				echo "no thanks"
+				echo "unrecognized subproject for server: '$SUBPROJECT'"
 				exit 1
 				;;
 		esac

live-build/lb_chroot_layered

@@ -132,6 +132,17 @@ reduce_pass_size () {
 		fi
 		p=$(dirname $f)
 		while [ "$p" != . ]; do
+			# As explained in the overlayfs documentation
+			# https://www.kernel.org/doc/html/latest/filesystems/overlayfs.html#whiteouts-and-opaque-directories
+			# an xattr of trusted.overlay.opaque indicates an 'opaque' directory
+			# that was deleted from the overlay. Removing files from within the
+			# directory, even if identical with one in the lower layer, will result
+			# in it going missing from the combined filesystem.
+			#
+			# It would be possible to be more clever, e.g. if the two directories
+			# are still similar, we could the delete the attribute and convert any
+			# still-needed deletions to whiteouts but it doesn't seem worth it in
+			# the cases seen so far.
 			if [ -n "$(getfattr -n trusted.overlay.opaque -h --only-values -- "$pass_dir/$p" 2>/dev/null)" ]; then
 				Echo_message "reduce_pass_size: '%s' would be removed from overlay but for trusted.overlay.opaque on '%s'" "$f" "$p"
 				continue 2

live-build/ubuntu-server/hooks/03-kernel-metapkg.chroot_early

@@ -4,14 +4,14 @@
 case $PASS in
     ubuntu-server.installer.*)
         flavor=${PASS##*.}
-	if [ "$flavor" = "generic" ]; then
+        if [ "$flavor" = "generic" ]; then
-		kernel_metapkg=linux-generic
+            kernel_metapkg=linux-generic
-	elif [ "$flavor" = "generic-hwe" ]; then
+        elif [ "$flavor" = "generic-hwe" ]; then
-		kernel_metapkg=linux-generic-hwe-$(lsb_release -sr)
+            kernel_metapkg=linux-generic-hwe-$(lsb_release -sr)
-	else
+        else
-		echo "bogus flavor: $flavor"
+            echo "bogus flavor: $flavor"
-		exit 1
+            exit 1
-	fi
+        fi
         ;;
     *)
         exit 0