properly update database when the databases= line is changed.  really.  you need this.

Reference: /n/atom/patch/applied2013/csdbline
Date: Wed Sep 11 03:23:54 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/ndb/cs.c	Wed Sep 11 03:23:37 2013
+++ /sys/src/cmd/ndb/cs.c	Wed Sep 11 03:23:39 2013
@@ -167,7 +167,7 @@
 
 /*
  *  net doesn't apply to (r)udp, icmp(v6), or telco (for speed).
- */
+  */
 Network network[] = {
 [Nilfast]	{ "il",		iplookup,	iptrans,	0, 1 },
 [Ntcp]		{ "tcp",	iplookup,	iptrans,	0, 0 },
@@ -350,7 +350,7 @@
 }
 
 void
-ndbinit(void)
+ndbinit0(void)
 {
 	db = ndbopen(dbfile);
 	if(db == nil)
@@ -363,6 +363,25 @@
 	}
 }
 
+void
+ndbinit(void)
+{
+	long t;
+	static int once;
+	static long t0;
+
+	t = time(0);
+	if(once == 0){
+		ndbinit0();
+		once = 1;
+		t0 = t;
+	}
+	else if(t - t0 > 30){
+		db = ndbreopendb(db);
+		t0 = t;
+	}
+}
+
 Mfile*
 newfid(int fid)
 {
@@ -822,6 +841,7 @@
 	}
 
 	/* start transaction with a clean slate */
+	ndbinit();
 	cleanmf(mf);
 
 	/*
@@ -1101,16 +1121,6 @@
 		if(strcmp(attr, "el") != 0)
 			myelname = strdup(p);
 	}
-	if(myelname == 0 && netdb != nil){
-		ndbreopen(netdb);
-		for(tt = t = ndbparse(netdb); t != nil; t = t->entry){
-			if(strcmp(t->attr, "el") == 0){
-				mysysname = strdup(t->val);
-				break;
-			}
-		}
-		ndbfree(tt);
-	}
 	if(myelname == 0){
 		snprint(buf, sizeof buf, "#l0/ether0/addr");
 		fd = open(buf, OREAD);
@@ -1120,11 +1130,21 @@
 		}
 		close(fd);
 	}
+	if(mysysname == 0 && myelname != 0 && netdb != nil){
+		ndbreopen(netdb);
+		for(tt = t = ndbparse(netdb); t != nil; t = t->entry){
+			if(strcmp(t->attr, "el") == 0){
+				mysysname = strdup(t->val);
+				break;
+			}
+		}
+		ndbfree(tt);
+	}
 	if(myelname != nil){
 		fd = open("/net/el/ctl", OWRITE);
 		if(fd != -1){
 			fprint(fd, "add %s", myelname);
-			fprint(fd, "bind ether #l0/ether0");
+		//	fprint(fd, "bind ether #l0/ether0");
 			if(mysysname != nil)
 				fprint(fd, "arpattr add sysname %s", mysysname); 	
 			close(fd);