the lnfs(4) man page refers to unlnfs, but it doesn't
appear to be distributed.

i've included a version i wrote in case you haven't got it.
(i don't know whether the version referred to was mine,
as i vaguely recall posting it, or someone else's. it's trivial
anyway).

Reference: /n/sources/patch/applied/unlnfs
Date: Thu Feb  3 13:57:39 CET 2005

--- /sys/src/cmd/unlnfs.c	Thu Jan  1 00:00:00 1970
+++ /sys/src/cmd/unlnfs.c	Thu Feb  3 13:57:39 2005
@@ -0,0 +1,114 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <libsec.h>
+
+enum
+{
+	ENCLEN = 26,
+};
+
+typedef struct Name Name;
+struct Name {
+	char		shortname[ENCLEN + 1];
+	char*	longname;
+	Name*	next;
+};
+
+Name *names;
+void rename(char*, char*, char*);
+void renamedir(char*);
+void readnames(char*);
+
+void
+main(int argc, char **argv)
+{
+	char lnfile[256], *d;
+	d = ".";
+	if(argc > 1)
+		d = argv[1];
+
+	snprint(lnfile, sizeof(lnfile), "%s/.longnames", d);
+	readnames(lnfile);
+	renamedir(d);
+}
+
+void
+renamedir(char *d)
+{
+	int n;
+	Dir *dir;
+	char *sub;
+	int fd, i;
+	uchar digest[MD5dlen];
+	Name *na;
+
+	fd = open(d, OREAD);
+	if (fd == -1)
+		return;
+	while((n = dirread(fd, &dir)) > 0){
+		for(i = 0; i < n; i++){
+			if(dir[i].mode & DMDIR){
+				sub = malloc(strlen(d) + 1 + strlen(dir[i].name) + 1);
+				sprint(sub, "%s/%s", d, dir[i].name);
+				renamedir(sub);
+				free(sub);
+			}
+			if(strlen(dir[i].name) != ENCLEN)
+				continue;
+			for (na = names; na != nil; na = na->next){
+				if (strcmp(na->shortname, dir[i].name) == 0){
+					rename(d, dir[i].name, na->longname);
+					break;
+				}
+			}
+		}
+		free(dir);
+	}
+	close(fd);
+}
+
+void
+rename(char *d, char *old, char *new)
+{
+	char *p;
+	Dir dir;
+	p = malloc(strlen(d) + 1 + strlen(old) + 1);
+	sprint(p, "%s/%s", d, old);
+	nulldir(&dir);
+	dir.name = new;
+	if(dirwstat(p, &dir) == -1)
+		fprint(2, "unlnfs: cannot rename %s to %s: %r\n", p, new);
+	free(p);
+}
+	
+void
+long2short(char shortname[ENCLEN+1], char *longname)
+{
+	uchar digest[MD5dlen];
+	md5((uchar*)longname, strlen(longname), digest, nil);
+	enc32(shortname, ENCLEN+1, digest, MD5dlen);
+}
+
+void
+readnames(char *lnfile)
+{
+	Biobuf *bio;
+	char *f;
+	int slot;
+	Name *n;
+
+	bio = Bopen(lnfile, OREAD);
+	if(bio == nil){
+		fprint(2, "unlnfs: cannot open %s: %r\n", lnfile);
+		exits("error");
+	}
+	while((f = Brdstr(bio, '\n', 1)) != nil){
+		n = malloc(sizeof(Name));
+		n->longname = f;
+		long2short(n->shortname, f);
+		n->next = names;
+		names = n;
+	}
+	Bterm(bio);
+}