--- /dev/null
+--- a/lib/command.c
++++ b/lib/command.c
+@@ -3064,6 +3064,13 @@ DEFUN (config_write_file,
+ VTY_NEWLINE);
+ goto finished;
+ }
++
++#if 0
++ /* This code fails on UNION MOUNTs and similar filesystems if the
++ * config file is still on the RO layer. Hardlinks across layers
++ * will not work and cause quagga to fail saving the configuration...
++ * should use rename() to move files around...
++ */
+ if (link (config_file, config_file_sav) != 0)
+ {
+ vty_out (vty, "Can't backup old configuration file %s.%s", config_file_sav,
+@@ -3077,7 +3084,23 @@ DEFUN (config_write_file,
+ VTY_NEWLINE);
+ goto finished;
+ }
++#else
++ /* And this is the code that hopefully does work */
++ if (rename (config_file, config_file_sav) != 0)
++ {
++ vty_out (vty, "Can't backup old configuration file %s.%s", config_file_sav,
++ VTY_NEWLINE);
++ goto finished;
++ }
++ sync ();
++#endif
++
++#if 0
++ /* same here. Please no cross-filesystem hardlinks... */
+ if (link (config_file_tmp, config_file) != 0)
++#else
++ if (rename (config_file_tmp, config_file) != 0)
++#endif
+ {
+ vty_out (vty, "Can't save configuration file %s.%s", config_file,
+ VTY_NEWLINE);