diff --git a/usr.bin/cksum/Makefile b/usr.bin/cksum/Makefile
index cabb6cfd1572..1cf3a7cee06f 100644
--- a/usr.bin/cksum/Makefile
+++ b/usr.bin/cksum/Makefile
@@ -1,7 +1,9 @@
 #	from: @(#)Makefile	8.1 (Berkeley) 6/6/93
-#	$Id: Makefile,v 1.3 1993/11/02 07:33:08 cgd Exp $
+#	$Id: Makefile,v 1.4 1995/01/15 06:43:49 mycroft Exp $
 
 PROG=	cksum
 SRCS=	cksum.c crc.c print.c sum1.c sum2.c
+LINKS=	${BINDIR}/cksum ${BINDIR}/sum
+MLINKS=	cksum.1 sum.1
 
 .include <bsd.prog.mk>
diff --git a/usr.bin/cksum/cksum.1 b/usr.bin/cksum/cksum.1
index 7738a220864d..0cf4f76088d2 100644
--- a/usr.bin/cksum/cksum.1
+++ b/usr.bin/cksum/cksum.1
@@ -33,7 +33,7 @@
 .\" SUCH DAMAGE.
 .\"
 .\"	from: @(#)cksum.1	8.1 (Berkeley) 6/29/93
-.\"	$Id: cksum.1,v 1.5 1994/05/20 06:14:31 jtc Exp $
+.\"	$Id: cksum.1,v 1.6 1995/01/15 06:43:51 mycroft Exp $
 .\"
 .Dd June 29, 1993
 .Dt CKSUM 1
@@ -45,6 +45,8 @@
 .Nm cksum
 .Op Fl o Ar \&1 No \&| Ar \&2
 .Op Ar file ...
+.Nm sum
+.Op Ar file ...
 .Sh DESCRIPTION
 The
 .Nm cksum
@@ -56,6 +58,14 @@ the total number of octets in the file and the file name.
 If no file name is specified, the standard input is used and no file name
 is written.
 .Pp
+The
+.Nm sum
+utility is identical to the
+.Nm cksum
+utility, except that it defaults to using historic algorithm 1, as
+described below.  It is provided for compatibility only, and should not
+be used by new programs.
+.Pp
 The options are as follows:
 .Bl -tag -width indent
 .It Fl o
@@ -142,7 +152,9 @@ The bit sequence is complemented and the result is the CRC.
 .Pp
 The
 .Nm cksum
-utility exits 0 on success, and >0 if an error occurs.
+and
+.Nm sum
+utilities exit 0 on success, and >0 if an error occurs.
 .Sh SEE ALSO
 The default calculation is identical to that given in pseudo-code
 in the following
@@ -162,5 +174,12 @@ utility is expected to conform to
 .Sh HISTORY
 The
 .Nm cksum
-utility appears in
+utility appeared in
 .Bx 4.4 .
+.\" .Pp
+.\" The
+.\" .Nm sum
+.\" utility appeared in
+.\" .Bx ?.?
+.\" and
+.\" .At V .
diff --git a/usr.bin/cksum/cksum.c b/usr.bin/cksum/cksum.c
index 754bced790c6..a91c96e6ddac 100644
--- a/usr.bin/cksum/cksum.c
+++ b/usr.bin/cksum/cksum.c
@@ -42,17 +42,20 @@ static char copyright[] =
 
 #ifndef lint
 /* from: static char sccsid[] = "@(#)cksum.c	8.1 (Berkeley) 6/6/93"; */
-static char *rcsid = "$Id: cksum.c,v 1.4 1994/12/24 16:02:45 cgd Exp $";
+static char *rcsid = "$Id: cksum.c,v 1.5 1995/01/15 06:43:52 mycroft Exp $";
 #endif /* not lint */
 
 #include <sys/cdefs.h>
 #include <sys/types.h>
-#include <fcntl.h>
-#include <unistd.h>
-#include <stdio.h>
+
+#include <err.h>
 #include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
+
 #include "extern.h"
 
 void usage __P((void));
@@ -62,27 +65,32 @@ main(argc, argv)
 	int argc;
 	char **argv;
 {
-	extern int optind;
 	u_int32_t len, val;
 	register int ch, fd, rval;
 	char *fn;
 	int (*cfncn) __P((int, u_int32_t *, u_int32_t *));
 	void (*pfncn) __P((char *, u_int32_t, u_int32_t));
+	extern char *__progname;
 
-	cfncn = crc;
-	pfncn = pcrc;
-	while ((ch = getopt(argc, argv, "o:")) != EOF)
+	if (!strcmp(__progname, "sum")) {
+		cfncn = csum1;
+		pfncn = psum1;
+	} else {
+		cfncn = crc;
+		pfncn = pcrc;
+	}
+
+	while ((ch = getopt(argc, argv, "o:")) != -1)
 		switch(ch) {
 		case 'o':
-			if (*optarg == '1') {
+			if (!strcmp(optarg, "1")) {
 				cfncn = csum1;
 				pfncn = psum1;
-			} else if (*optarg == '2') {
+			} else if (!strcmp(optarg, "2")) {
 				cfncn = csum2;
 				pfncn = psum2;
 			} else {
-				(void)fprintf(stderr,
-				    "cksum: illegal argument to -o option\n");
+				warnx("illegal argument to -o option");
 				usage();
 			}
 			break;
@@ -100,15 +108,13 @@ main(argc, argv)
 		if (*argv) {
 			fn = *argv++;
 			if ((fd = open(fn, O_RDONLY, 0)) < 0) {
-				(void)fprintf(stderr, "cksum: %s: %s\n",
-				    fn, strerror(errno));
+				warn("%s", fn);
 				rval = 1;
 				continue;
 			}
 		}
 		if (cfncn(fd, &val, &len)) {
-			(void)fprintf(stderr, "cksum: %s: %s\n",
-			    fn ? fn : "stdin", strerror(errno));
+			warn("%s", fn ? fn : "stdin");
 			rval = 1;
 		} else
 			pfncn(fn, val, len);
@@ -120,6 +126,7 @@ main(argc, argv)
 void
 usage()
 {
+
 	(void)fprintf(stderr, "usage: cksum [-o 1 | 2] [file ...]\n");
 	exit(1);
 }