When I run nmbd with option -l /var/log/samba, log-file
nmbd.log was created in /usr/local/samba/var (default) 
directory.

This patch is trivial remedy:

diff -r -U3 samba-3.0.1/source/nmbd/nmbd.c samba-3.0.1-karl/source/nmbd/nmbd.c
--- samba-3.0.1/source/nmbd/nmbd.c      Fri Dec 26 17:18:18 2003
+++ samba-3.0.1-karl/source/nmbd/nmbd.c Fri Dec 26 16:53:44 2003
@@ -595,7 +595,7 @@
  **************************************************************************** */
  int main(int argc, const char *argv[])
 {
-       pstring logfile;
+//     pstring logfile;
        static BOOL opt_interactive;
        poptContext pc;
        int opt;
@@ -623,8 +623,8 @@

        sys_srandom(time(NULL) ^ sys_getpid());

-       slprintf(logfile, sizeof(logfile)-1, "%s/log.nmbd", dyn_LOGFILEBASE);
-       lp_set_logfile(logfile);
+//     slprintf(logfile, sizeof(logfile)-1, "%s/log.nmbd", dyn_LOGFILEBASE);
+//     lp_set_logfile(logfile);

        fault_setup((void (*)(void *))fault_continue );