--- /sys/src/cmd/aux/randfs.c	Thu Feb 26 00:00:00 2015
+++ /sys/src/cmd/aux/randfs.c	Thu Feb 26 00:00:00 2015
@@ -0,0 +1,217 @@
+#include <u.h>
+#include <libc.h>
+#include <auth.h>
+#include <fcall.h>
+#include <thread.h>
+#include <9p.h>
+
+enum
+{
+	Qroot,
+	Qrandom,
+	Nqid,
+};
+
+static int
+fillstat(ulong qid, Dir *d)
+{
+	memset(d, 0, sizeof *d);
+
+	d->uid = "sys";
+	d->gid = "sys";
+	d->muid = "";
+	d->qid = (Qid){qid, 0, 0};
+	d->atime = time(0);
+
+	switch(qid) {
+	case Qroot:
+		d->name = "/";
+		d->qid.type = QTDIR;
+		d->mode = DMDIR|0777;
+		break;
+	case Qrandom:
+		d->name = "random";
+		d->mode = 0444;
+		break;
+	}
+	return 1;
+}
+
+static int
+readtopdir(Fid*, uchar *buf, long off, int cnt, int blen)
+{
+	int i, m, n;
+	long pos;
+	Dir d;
+
+	n = 0;
+	pos = 0;
+	for (i = 1; i < Nqid; i++){
+		fillstat(i, &d);
+		m = convD2M(&d, &buf[n], blen-n);
+		if(off <= pos){
+			if(m <= BIT16SZ || m > cnt)
+				break;
+			n += m;
+			cnt -= m;
+		}
+		pos += m;
+	}
+	return n;
+}
+
+static ulong
+randomread(void *xp, ulong n)
+{
+	uchar *e, *p;
+
+	p = xp;
+
+	for(e = p + n; p < e; )
+		*p++ = rand();
+
+	return n;
+}
+
+static void
+fsattach(Req *r)
+{
+	char *spec;
+
+	spec = r->ifcall.aname;
+	if(spec && spec[0]){
+		respond(r, "invalid attach specifier");
+		return;
+	}
+	r->ofcall.qid = (Qid){Qroot, 0, QTDIR};
+	r->fid->qid = r->ofcall.qid;
+	respond(r, nil);
+}
+
+static void
+fsstat(Req *r)
+{
+	fillstat((ulong)r->fid->qid.path, &r->d);
+
+	r->d.name = estrdup9p(r->d.name);
+	r->d.uid = estrdup9p(r->d.uid);
+	r->d.gid = estrdup9p(r->d.gid);
+	r->d.muid = estrdup9p(r->d.muid);
+
+	respond(r, nil);
+}
+
+static char*
+fswalk1(Fid *fid, char *name, Qid *qid)
+{
+	switch((ulong)fid->qid.path) {
+	case Qroot:
+		if (strcmp(name, "..") == 0) {
+			*qid = (Qid){Qroot, 0, QTDIR};
+			fid->qid = *qid;
+			return nil;
+		}
+		if (strcmp(name, "random") == 0) {
+			*qid = (Qid){Qrandom, 0, 0};
+			fid->qid = *qid;
+			return nil;
+		}
+		return "file not found";
+
+	default:
+		return "walk in non-directory";
+	}
+}
+
+void
+fsread(Req *r)
+{
+	vlong offset;
+	long count;
+	uchar *b;
+
+	b = (uchar*)r->ofcall.data;
+	offset = r->ifcall.offset;
+	count = r->ifcall.count;
+
+	switch((ulong)r->fid->qid.path) {
+	case Qroot:
+		r->ofcall.count = readtopdir(r->fid, b, offset, count, count);
+		respond(r, nil);
+		return;
+
+	case Qrandom:
+		r->ofcall.count = randomread(b, count);
+		respond(r, nil);
+		return;
+	}
+}
+
+void
+fsopen(Req *r)
+{
+	switch((ulong)r->fid->qid.path) {
+	case Qroot:
+		respond(r, nil);
+		return;
+
+	case Qrandom:
+		srand(truerand());
+		respond(r, nil);
+		return;
+	}
+}
+
+Srv fs = {
+	.attach=	fsattach,
+	.open=	fsopen,
+	.read=	fsread,
+	.stat=	fsstat,
+	.walk1=	fswalk1,
+};
+
+void
+usage(void)
+{
+	fprint(2, "usage: randfs [-D] [-s srvname] [-m mtpt]\n");
+	exits("usage");
+}
+
+void
+main(int argc, char **argv)
+{
+	char *addr = nil;
+	char *srvname = nil;
+	char *mtpt = nil;
+
+	ARGBEGIN{
+	case 'D':
+		chatty9p++;
+		break;
+	case 'a':
+		addr = EARGF(usage());
+		break;
+	case 's':
+		srvname = EARGF(usage());
+		break;
+	case 'm':
+		mtpt = EARGF(usage());
+		break;
+	default:
+		usage();
+	}ARGEND;
+
+	if(argc)
+		usage();
+
+	if(chatty9p)
+		fprint(2, "randsrv.nopipe %d srvname %s mtpt %s\n", fs.nopipe, srvname, mtpt);
+	if(addr == nil && srvname == nil && mtpt == nil)
+		sysfatal("must specify -a, -s, or -m option");
+	if(addr)
+		listensrv(&fs, addr);
+
+	if(srvname || mtpt)
+		postmountsrv(&fs, srvname, mtpt, MBEFORE);
+	exits(0);
+}
--- /n/sources/plan9/sys/src/cmd/aux/mkfile	Thu Aug 16 22:50:45 2012
+++ /sys/src/cmd/aux/mkfile	Thu Feb 26 00:00:00 2015
@@ -26,6 +26,7 @@
 	olefs\
 	pcmcia\
 	portmap\
+	randfs\
 	rdwr\
 	reboot\
 	searchfs\