+AC_ARG_ENABLE(backend,AC_HELP_STRING([--enable-backend=<backend>],[Choose the backend database to use. Defaults to db3.]), [], [enable_backend="db3"])
+
+AC_MSG_CHECKING([which key database backend to use])
+AC_MSG_RESULT([$enable_backend])
+AC_CHECK_FILE(keydb_$enable_backend.c, ,AC_MSG_ERROR([non existent key database backend $enable_backend]))
+
+if test "x$enable_backend" = "xdb3"
+then
+ AC_CHECK_LIB(db3, db_env_create,,
+ AC_MSG_ERROR([cannot compile DB3 backend without libdb3]))
+else if test "x$enable_backend" = "xpg"
+then
+ AC_CHECK_LIB(pq, PQsetdbLogin,,
+ AC_MSG_ERROR([cannot compile PostgreSQL backend without libpq]))
+fi
+fi
+
+AC_SUBST(DBTYPE, $enable_backend)
+