diff --git a/sbin/newfs/Makefile b/sbin/newfs/Makefile
index aa4b22fc601a..072b0b7a749d 100644
--- a/sbin/newfs/Makefile
+++ b/sbin/newfs/Makefile
@@ -1,4 +1,4 @@
-#	$NetBSD: Makefile,v 1.35 2009/12/20 15:21:13 dsl Exp $
+#	$NetBSD: Makefile,v 1.36 2010/08/09 17:20:57 pooka Exp $
 #	@(#)Makefile	8.2 (Berkeley) 3/27/94
 
 .include <bsd.own.mk>
@@ -12,6 +12,7 @@ DISKLABEL=${NETBSDSRCDIR}/sbin/disklabel
 FSCK=${NETBSDSRCDIR}/sbin/fsck
 MOUNT=${NETBSDSRCDIR}/sbin/mount
 CPPFLAGS+=-DMFS -I${.CURDIR} -I${DISKLABEL} -I${FSCK} -I${MOUNT}
+CPPFLAGS+=-DGARBAGE
 
 DPADD+= ${LIBUTIL}
 LDADD+= -lutil
diff --git a/sbin/newfs/mkfs.c b/sbin/newfs/mkfs.c
index f1c314e71171..546274c57382 100644
--- a/sbin/newfs/mkfs.c
+++ b/sbin/newfs/mkfs.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: mkfs.c,v 1.107 2010/01/31 16:04:34 mlelstv Exp $	*/
+/*	$NetBSD: mkfs.c,v 1.108 2010/08/09 17:20:57 pooka Exp $	*/
 
 /*
  * Copyright (c) 1980, 1989, 1993
@@ -73,7 +73,7 @@
 #if 0
 static char sccsid[] = "@(#)mkfs.c	8.11 (Berkeley) 5/3/95";
 #else
-__RCSID("$NetBSD: mkfs.c,v 1.107 2010/01/31 16:04:34 mlelstv Exp $");
+__RCSID("$NetBSD: mkfs.c,v 1.108 2010/08/09 17:20:57 pooka Exp $");
 #endif
 #endif /* not lint */
 
@@ -157,6 +157,18 @@ int iobuf_memsize;		/* Actual buffer size */
 
 int	fsi, fso;
 
+static void
+fserr(int num)
+{
+#ifdef GARBAGE
+	extern int Gflag;
+
+	if (Gflag)
+		return;
+#endif
+	exit(num);
+}
+
 void
 mkfs(const char *fsys, int fi, int fo,
     mode_t mfsmode, uid_t mfsuid, gid_t mfsgid)
@@ -207,12 +219,12 @@ mkfs(const char *fsys, int fi, int fo,
 	if (sblock.fs_avgfilesize <= 0) {
 		printf("illegal expected average file size %d\n",
 		    sblock.fs_avgfilesize);
-		exit(14);
+		fserr(14);
 	}
 	if (sblock.fs_avgfpdir <= 0) {
 		printf("illegal expected number of files per directory %d\n",
 		    sblock.fs_avgfpdir);
-		exit(15);
+		fserr(15);
 	}
 	/*
 	 * collect and verify the block and fragment sizes
@@ -222,32 +234,32 @@ mkfs(const char *fsys, int fi, int fo,
 	if (!powerof2(sblock.fs_bsize)) {
 		printf("block size must be a power of 2, not %d\n",
 		    sblock.fs_bsize);
-		exit(16);
+		fserr(16);
 	}
 	if (!powerof2(sblock.fs_fsize)) {
 		printf("fragment size must be a power of 2, not %d\n",
 		    sblock.fs_fsize);
-		exit(17);
+		fserr(17);
 	}
 	if (sblock.fs_fsize < sectorsize) {
 		printf("fragment size %d is too small, minimum is %d\n",
 		    sblock.fs_fsize, sectorsize);
-		exit(18);
+		fserr(18);
 	}
 	if (sblock.fs_bsize < MINBSIZE) {
 		printf("block size %d is too small, minimum is %d\n",
 		    sblock.fs_bsize, MINBSIZE);
-		exit(19);
+		fserr(19);
 	}
 	if (sblock.fs_bsize > MAXBSIZE) {
 		printf("block size %d is too large, maximum is %d\n",
 		    sblock.fs_bsize, MAXBSIZE);
-		exit(19);
+		fserr(19);
 	}
 	if (sblock.fs_bsize < sblock.fs_fsize) {
 		printf("block size (%d) cannot be smaller than fragment size (%d)\n",
 		    sblock.fs_bsize, sblock.fs_fsize);
-		exit(20);
+		fserr(20);
 	}
 
 	if (maxbsize < bsize || !powerof2(maxbsize)) {
@@ -282,7 +294,7 @@ mkfs(const char *fsys, int fi, int fo,
 			"minimum with block size %d is %d\n",
 		    sblock.fs_fsize, sblock.fs_bsize,
 		    sblock.fs_bsize / MAXFRAG);
-		exit(21);
+		fserr(21);
 	}
 	sblock.fs_fsbtodb = ilog2(sblock.fs_fsize / sectorsize);
 	sblock.fs_size = dbtofsb(&sblock, fssize);
@@ -290,7 +302,7 @@ mkfs(const char *fsys, int fi, int fo,
 		if ((uint64_t)sblock.fs_size >= 1ull << 31) {
 			printf("Too many fragments (0x%" PRIx64
 			    ") for a FFSv1 filesystem\n", sblock.fs_size);
-			exit(22);
+			fserr(22);
 		}
 		sblock.fs_magic = FS_UFS1_MAGIC;
 		sblock.fs_sblockloc = SBLOCK_UFS1;
@@ -353,7 +365,7 @@ mkfs(const char *fsys, int fi, int fo,
 	if (sblock.fs_size < sblock.fs_iblkno + 3 * sblock.fs_frag) {
 		printf("Filesystem size %lld < minimum size of %d\n",
 		    (long long)sblock.fs_size, sblock.fs_iblkno + 3 * sblock.fs_frag);
-		exit(23);
+		fserr(23);
 	}
 	if (num_inodes != 0)
 		inodeblks = howmany(num_inodes, INOPB(&sblock));
@@ -420,7 +432,7 @@ mkfs(const char *fsys, int fi, int fo,
 	if ((int)CGSIZE(&sblock) > sblock.fs_bsize) {
 		printf("CGSIZE miscalculated %d > %d\n",
 		    (int)CGSIZE(&sblock), sblock.fs_bsize);
-		exit(24);
+		fserr(24);
 	}
 
 	sblock.fs_dblkno = sblock.fs_iblkno + sblock.fs_ipg / INOPF(&sblock);
@@ -574,7 +586,7 @@ mkfs(const char *fsys, int fi, int fo,
 		 */
 		if (fssize <= 0) {
 			printf("preposterous size %lld\n", (long long)fssize);
-			exit(13);
+			fserr(13);
 		}
 		wtfs(fssize - 1, sectorsize, iobuf);
 
@@ -756,7 +768,7 @@ initcg(int cylno, const struct timeval *tv)
 		if (dupper >= cgstart(&sblock, cylno + 1)) {
 			printf("\rToo many cylinder groups to fit summary "
 				"information into first cylinder group\n");
-			exit(40);
+			fserr(40);
 		}
 	}
 	memset(&acg, 0, sblock.fs_cgsize);
@@ -809,7 +821,7 @@ initcg(int cylno, const struct timeval *tv)
 	}
 	if (acg.cg_nextfreeoff > sblock.fs_cgsize) {
 		printf("Panic: cylinder group too big\n");
-		exit(37);
+		fserr(37);
 	}
 	acg.cg_cs.cs_nifree += sblock.fs_ipg;
 	if (cylno == 0)
@@ -1228,7 +1240,7 @@ iput(union dinode *ip, ino_t ino)
 		ffs_cg_swap(&acg, &acg, &sblock);
 	if (acg.cg_magic != CG_MAGIC) {
 		printf("cg 0: bad magic number\n");
-		exit(31);
+		fserr(31);
 	}
 	acg.cg_cs.cs_nifree--;
 	setbit(cg_inosused(&acg, 0), ino);
@@ -1241,7 +1253,7 @@ iput(union dinode *ip, ino_t ino)
 	if (ino >= (ino_t)(sblock.fs_ipg * sblock.fs_ncg)) {
 		printf("fsinit: inode value out of range (%llu).\n",
 		    (unsigned long long)ino);
-		exit(32);
+		fserr(32);
 	}
 	d = fsbtodb(&sblock, ino_to_fsba(&sblock, ino));
 	rdfs(d, sblock.fs_bsize, (char *)iobuf);
diff --git a/sbin/newfs/newfs.8 b/sbin/newfs/newfs.8
index d8ea842c8641..aecaceb19f60 100644
--- a/sbin/newfs/newfs.8
+++ b/sbin/newfs/newfs.8
@@ -1,4 +1,4 @@
-.\"	$NetBSD: newfs.8,v 1.77 2010/02/21 13:26:46 wiz Exp $
+.\"	$NetBSD: newfs.8,v 1.78 2010/08/09 17:20:57 pooka Exp $
 .\"
 .\" Copyright (c) 1983, 1987, 1991, 1993, 1994
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)newfs.8	8.6 (Berkeley) 5/3/95
 .\"
-.Dd December 1, 2009
+.Dd August 9, 2010
 .Dt NEWFS 8
 .Os
 .Sh NAME
@@ -37,7 +37,7 @@
 .Nd construct a new file system
 .Sh SYNOPSIS
 .Nm
-.Op Fl FINZ
+.Op Fl FGINZ
 .Op Fl a Ar maxcontig
 .Op Fl B Ar byte-order
 .Op Fl b Ar block-size
@@ -157,6 +157,10 @@ The default size depends upon the size of the file system:
 .El
 .It Fl g Ar avgfilesize
 The expected average file size for the file system.
+.It Fl G
+Treat garbage parameters as non-fatal.
+Using this option may result in a file system which causes a kernel
+panic and should only be used for testing.
 .It Fl h Ar avgfpdir
 The expected average number of files per directory on the file system.
 .It Fl I
diff --git a/sbin/newfs/newfs.c b/sbin/newfs/newfs.c
index 037ca6956382..7023f2bcbb00 100644
--- a/sbin/newfs/newfs.c
+++ b/sbin/newfs/newfs.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: newfs.c,v 1.106 2009/12/20 15:21:13 dsl Exp $	*/
+/*	$NetBSD: newfs.c,v 1.107 2010/08/09 17:20:57 pooka Exp $	*/
 
 /*
  * Copyright (c) 1983, 1989, 1993, 1994
@@ -78,7 +78,7 @@ __COPYRIGHT("@(#) Copyright (c) 1983, 1989, 1993, 1994\
 #if 0
 static char sccsid[] = "@(#)newfs.c	8.13 (Berkeley) 5/1/95";
 #else
-__RCSID("$NetBSD: newfs.c,v 1.106 2009/12/20 15:21:13 dsl Exp $");
+__RCSID("$NetBSD: newfs.c,v 1.107 2010/08/09 17:20:57 pooka Exp $");
 #endif
 #endif /* not lint */
 
@@ -200,6 +200,7 @@ const char lmsg[] = "%s: can't read disk label";
 
 
 int	mfs;			/* run as the memory based filesystem */
+int	Gflag;			/* allow garbage parameters (for testing) */
 int	Nflag;			/* run without writing file system */
 int	Oflag = 1;		/* format as an 4.3BSD file system */
 int	verbosity;		/* amount of printf() output */
@@ -269,7 +270,7 @@ main(int argc, char *argv[])
 
 	opstring = mfs ?
 	    "NT:V:a:b:d:e:f:g:h:i:m:n:o:p:s:u:" :
-	    "B:FINO:S:T:V:Za:b:d:e:f:g:h:i:l:m:n:o:r:s:v:";
+	    "B:FGINO:S:T:V:Za:b:d:e:f:g:h:i:l:m:n:o:r:s:v:";
 	while ((ch = getopt(argc, argv, opstring)) != -1)
 		switch (ch) {
 		case 'B':
@@ -287,6 +288,11 @@ main(int argc, char *argv[])
 		case 'F':
 			Fflag = 1;
 			break;
+		case 'G':
+			fprintf(stderr, "WARNING: -G may create file systems "
+			    "which cause kernel panics\n");
+			Gflag = 1;
+			break;
 		case 'I':
 			Iflag = 1;
 			break;
@@ -781,12 +787,24 @@ strsuftoi64(const char *desc, const char *arg, int64_t min, int64_t max, int *nu
 	result = r1 << shift;
 	if (errno == ERANGE || result >> shift != r1)
 		errx(1, "%s `%s' is too large to convert.", desc, arg);
-	if (result < min)
-		errx(1, "%s `%s' (%" PRId64 ") is less than the minimum (%" PRId64 ").",
-		    desc, arg, result, min);
-	if (result > max)
-		errx(1, "%s `%s' (%" PRId64 ") is greater than the maximum (%" PRId64 ").",
-		    desc, arg, result, max);
+	if (result < min) {
+		if (Gflag) {
+			warnx("%s `%s' (%" PRId64 ") is less than the "
+			    "minimum (%" PRId64 ").", desc, arg, result, min);
+		} else {
+			errx(1, "%s `%s' (%" PRId64 ") is less than the "
+			    "minimum (%" PRId64 ").", desc, arg, result, min);
+		}
+	}
+	if (result > max) {
+		if (Gflag) {
+			warnx("%s `%s' (%" PRId64 ") is greater than the "
+			    "maximum (%" PRId64 ").", desc, arg, result, max);
+		} else {
+			errx(1, "%s `%s' (%" PRId64 ") is greater than the "
+			    "maximum (%" PRId64 ").", desc, arg, result, max);
+		}
+	}
 	return result;
 }