diff --git a/appliance/Makefile.am b/appliance/Makefile.am
index 9c85c6904..28ae06b91 100644
--- a/appliance/Makefile.am
+++ b/appliance/Makefile.am
@@ -49,9 +49,9 @@ superminfs_DATA += \
 	supermin.d/hostfiles
 endif
 
-# This used to be a configure-generated file (as is update.sh still).
-# However config.status always touches the destination file, which
-# means the appliance got rebuilt too often.
+# This used to be a configure-generated file.  However config.status
+# always touches the destination file, which means the appliance got
+# rebuilt too often.
 make.sh: make.sh.in $(top_builddir)/config.log $(top_builddir)/config.status
 	cd $(top_builddir) && \
 	  ./config.status --file=appliance/$@-t:appliance/$<
@@ -59,7 +59,7 @@ make.sh: make.sh.in $(top_builddir)/config.log $(top_builddir)/config.status
 	cmp -s $@ $@-t || mv $@-t $@
 	rm -f $@-t
 
-PACKAGELIST_CPP_FLAGS = -D$(DISTRO)=1
+PACKAGELIST_CPP_FLAGS = -D$(DISTRO)=1 -DEXTRA_PACKAGES="$(EXTRA_PACKAGES)"
 if VALGRIND_DAEMON
 PACKAGELIST_CPP_FLAGS += -DVALGRIND_DAEMON=1
 endif
diff --git a/appliance/packagelist.in b/appliance/packagelist.in
index a43039c17..6c2172fd7 100644
--- a/appliance/packagelist.in
+++ b/appliance/packagelist.in
@@ -11,6 +11,10 @@
  *
  * There is also a list of packages which are excluded if they appear
  * as dependencies of the packages below.  See: excludelist.in
+ *
+ * To add arbitrary extra packages, use:
+ *
+ *   ./configure --with-extra-packages="gdb valgrind [etc]"
  */
 
 /* Basically the same with a few minor tweaks. */
@@ -160,7 +164,5 @@ zerofree
 valgrind
 #endif
 
-/* Enable this to add useful debugging tools to the appliance. */
-#if 0
-gdb
-#endif
+/* Define this by doing: ./configure --with-extra-packages="..." */
+EXTRA_PACKAGES
diff --git a/configure.ac b/configure.ac
index e08aacc5b..7059867c2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -489,6 +489,14 @@ fi
 AC_MSG_RESULT([$DISTRO])
 AC_SUBST([DISTRO])
 
+dnl Add extra packages to the appliance.
+AC_ARG_WITH([extra-packages],
+    [AS_HELP_STRING([--with-extra-packages],
+                    [add extra packages to the appliance])],
+    [EXTRA_PACKAGES="$withval"],
+    [EXTRA_PACKAGES=])
+AC_SUBST([EXTRA_PACKAGES])
+
 dnl Check for rpcgen and XDR library.  rpcgen is optional.
 AC_CHECK_PROG([RPCGEN],[rpcgen],[rpcgen],[no])
 AM_CONDITIONAL([HAVE_RPCGEN],[test "x$RPCGEN" != "xno"])