diff --git a/usr.bin/mkimg/mkimg.h b/usr.bin/mkimg/mkimg.h
--- a/usr.bin/mkimg/mkimg.h
+++ b/usr.bin/mkimg/mkimg.h
@@ -29,6 +29,10 @@
 
 #include <sys/queue.h>
 #include <sys/types.h>
+#include <stdbool.h>
+
+extern bool reproducible;
+extern time_t source_date_epoch;
 
 struct part {
 	TAILQ_ENTRY(part) link;
diff --git a/usr.bin/mkimg/mkimg.1 b/usr.bin/mkimg/mkimg.1
--- a/usr.bin/mkimg/mkimg.1
+++ b/usr.bin/mkimg/mkimg.1
@@ -41,6 +41,7 @@
 .Op Fl f Ar format
 .Op Fl o Ar outfile
 .Op Fl a Ar active
+.Op Fl R
 .Op Fl v
 .Op Fl y
 .Op Fl s Ar scheme Op Fl p Ar partition ...
@@ -138,6 +139,13 @@
 same time.
 .Pp
 The
+.Fl R
+option enables reproducible mode: any timestamps or random identifiers will
+be fixed so as to ensure consistent output.
+See also the description of
+.Ev SOURCE_DATE_EPOCH .
+.Pp
+The
 .Fl v
 option increases the level of output that the
 .Nm
@@ -329,6 +337,9 @@
 .It Ev TMPDIR
 Directory to put temporary files in; default is
 .Pa /tmp .
+.It Ev SOURCE_DATE_EPOCH
+The source of any timestamps embedded in the output file.
+The value must be an ASCII representation of a UNIX timestamp.
 .El
 .Sh EXAMPLES
 To create a bootable disk image that is partitioned using the GPT scheme and
diff --git a/usr.bin/mkimg/mkimg.c b/usr.bin/mkimg/mkimg.c
--- a/usr.bin/mkimg/mkimg.c
+++ b/usr.bin/mkimg/mkimg.c
@@ -61,6 +61,9 @@
 static uint64_t min_capacity = 0;
 static uint64_t max_capacity = 0;
 
+bool reproducible = false;
+time_t source_date_epoch = -1;
+
 struct partlisthead partlist = TAILQ_HEAD_INITIALIZER(partlist);
 u_int nparts = 0;
 
@@ -555,13 +558,23 @@
 int
 main(int argc, char *argv[])
 {
-	const char *format_name;
+	const char *format_name, *var;
 	int bcfd, outfd;
 	int c, error;
 
+	var = getenv("SOURCE_DATE_EPOCH");
+	if (var != NULL) {
+		char *end;
+
+		errno = 0;
+		source_date_epoch = (time_t)strtoul(var, &end, 10);
+		if (*end != '\0' || errno != 0 || source_date_epoch < 0)
+			errx(EX_DATAERR, "invalid SOURCE_DATE_EPOCH");
+	}
+
 	bcfd = -1;
 	outfd = 1;	/* Write to stdout by default */
-	while ((c = getopt_long(argc, argv, "a:b:c:C:f:o:p:s:vyH:P:S:T:",
+	while ((c = getopt_long(argc, argv, "a:b:c:C:f:o:p:s:vyH:P:RS:T:",
 	    longopts, NULL)) != -1) {
 		switch (c) {
 		case 'a':	/* ACTIVE PARTITION, if supported */
@@ -606,6 +619,9 @@
 			if (error)
 				errc(EX_DATAERR, error, "partition");
 			break;
+		case 'R':
+			reproducible = true;
+			break;
 		case 's':	/* SCHEME */
 			if (scheme_selected() != NULL)
 				usage("multiple schemes given");
@@ -675,6 +691,9 @@
 	if (max_capacity != 0 && min_capacity > max_capacity)
 		usage("minimum capacity cannot be larger than the maximum one");
 
+	if (reproducible)
+		srandom(42);
+
 	if (secsz > blksz) {
 		if (blksz != 0)
 			errx(EX_DATAERR, "the physical block size cannot "
diff --git a/usr.bin/mkimg/uuid.c b/usr.bin/mkimg/uuid.c
--- a/usr.bin/mkimg/uuid.c
+++ b/usr.bin/mkimg/uuid.c
@@ -45,20 +45,9 @@
 }
 #endif	/* __APPLE__ */
 
-#ifdef __FreeBSD__
-#include <sys/uuid.h>
-
-static void
-osdep_uuidgen(mkimg_uuid_t *uuid)
-{
-
-	uuidgen((void *)uuid, 1);
-}
-#endif	/* __FreeBSD__ */
-
-#ifdef __linux__
+#if defined(__linux__) || defined(__FreeBSD__)
+#include <sys/time.h>
 #include <stdlib.h>
-#include <time.h>
 
 static void
 osdep_uuidgen(mkimg_uuid_t *uuid)
@@ -68,7 +57,12 @@
 	u_int i;
 	uint16_t seq;
 
-	if (gettimeofday(&tv, NULL) == -1)
+	if (reproducible)
+		memset(&tv, 0, sizeof(tv));
+	else if (source_date_epoch >= 0) {
+		tv.tv_sec = source_date_epoch;
+		tv.tv_usec = 0;
+	} else if (gettimeofday(&tv, NULL) == -1)
 		abort();
 
 	time += (uint64_t)tv.tv_sec * 10000000LL;