Index: usr.bin/mkuzip/mkuzip.8
===================================================================
--- usr.bin/mkuzip/mkuzip.8
+++ usr.bin/mkuzip/mkuzip.8
@@ -37,7 +37,7 @@
 .Nm
 .Op Fl v
 .Op Fl o Ar outfile
-.Op Fl s Ar cluster_size
+.Op Fl s Ar cluster_size Op Fl t Ar trimto
 .Op Fl j Ar compression_jobs
 .Ar infile
 .Sh DESCRIPTION
@@ -131,6 +131,10 @@
 .Va hw.ncpu
 .Xr sysctl 8
 variable.
+.It Fl t Ar trimto
+Limit the compressed image size to
+.Ar trimto
+blocks.
 .El
 .Sh NOTES
 The compression ratio largely depends on the cluster size used.
Index: usr.bin/mkuzip/mkuzip.c
===================================================================
--- usr.bin/mkuzip/mkuzip.c
+++ usr.bin/mkuzip/mkuzip.c
@@ -110,6 +110,8 @@
 	struct mkuz_blk_info *chit;
 	size_t ncpusz, ncpu;
 	double st, et;
+	int blksz_set;
+	long long trim_nblocks;
 
 	st = getdtime();
 
@@ -131,8 +133,10 @@
 	cfs.handler = &uzip_fmt;
 	cfs.nworkers = ncpu;
 	struct mkuz_blk *iblk, *oblk;
+	blksz_set = 0;
+	trim_nblocks = -1;
 
-	while((opt = getopt(argc, argv, "o:s:vZdLSj:")) != -1) {
+	while((opt = getopt(argc, argv, "o:s:vZdLSj:t:")) != -1) {
 		switch(opt) {
 		case 'o':
 			oname = optarg;
@@ -146,6 +150,7 @@
 				/* Not reached */
 			}
 			cfs.blksz = tmp;
+			blksz_set = 1;
 			break;
 
 		case 'v':
@@ -179,6 +184,15 @@
 			cfs.nworkers = tmp;
 			break;
 
+		case 't':
+			trim_nblocks = atoll(optarg);
+			if (trim_nblocks <= 0) {
+				errx(1, "invalid number of blocks specified:"
+				    " %s", optarg);
+				/* Not reached */
+			}
+			break;
+
 		default:
 			usage();
 			/* Not reached */
@@ -191,6 +205,11 @@
 		usage();
 		/* Not reached */
 	}
+	if (blksz_set == 0 && trim_nblocks > 0) {
+		errx(1, "cluster size needs to be specified explicitly when "
+		    "using -t option");
+		/* Not reached */
+	}
 
 	strcpy(hdr.magic, cfs.handler->magic);
 
@@ -247,6 +266,14 @@
 			"of %d, padding data\n", cfs.blksz);
 		hdr.nblocks++;
 	}
+	if (trim_nblocks > 0) {
+		if (trim_nblocks > hdr.nblocks) {
+			errx(1, "requested trim size (%lld) is greater than "
+			    "projected size (%u)", trim_nblocks, hdr.nblocks);
+			/* Not reached */
+		}
+		hdr.nblocks = trim_nblocks;
+	}
 	toc = mkuz_safe_malloc((hdr.nblocks + 1) * sizeof(*toc));
 
 	cfs.fdw = open(oname, (cfs.en_dedup ? O_RDWR : O_WRONLY) | O_TRUNC | O_CREAT,
@@ -408,8 +435,8 @@
 usage(void)
 {
 
-	fprintf(stderr, "usage: mkuzip [-vZdLS] [-o outfile] [-s cluster_size] "
-	    "[-j ncompr] infile\n");
+	fprintf(stderr, "usage: mkuzip [-vZdLS] [-o outfile] [-s cluster_size "
+	    "[-t trimto]] [-j ncompr] infile\n");
 	exit(1);
 }