diff --git a/sbin/newfs/mkfs.c b/sbin/newfs/mkfs.c
index 398f36961f60..4ca25a23f495 100644
--- a/sbin/newfs/mkfs.c
+++ b/sbin/newfs/mkfs.c
@@ -44,6 +44,8 @@ static char sccsid[] = "@(#)mkfs.c	8.3 (Berkeley) 2/3/94";
 #include <ufs/ufs/dir.h>
 #include <ufs/ffs/fs.h>
 #include <sys/disklabel.h>
+#include <sys/file.h>
+#include <sys/mman.h>
 
 #ifndef STANDALONE
 #include <a.out.h>
@@ -100,6 +102,7 @@ extern int	sbsize;		/* superblock size */
 extern u_long	memleft;	/* virtual memory available */
 extern caddr_t	membase;	/* start address of memory based filesystem */
 extern caddr_t	malloc(), calloc();
+extern char *	filename;
 
 union {
 	struct fs fs;
@@ -129,7 +132,7 @@ mkfs(pp, fsys, fi, fo)
 	long used, mincpgcnt, bpcg;
 	long mapcramped, inodecramped;
 	long postblsize, rotblsize, totalsbsize;
-	int ppid, status;
+	int ppid, status, fd;
 	time_t utime;
 	quad_t sizepb;
 	void started();
@@ -151,10 +154,41 @@ mkfs(pp, fsys, fi, fo)
 			/* NOTREACHED */
 		}
 		(void)malloc(0);
-		if (fssize * sectorsize > memleft)
-			fssize = (memleft - 16384) / sectorsize;
-		if ((membase = malloc(fssize * sectorsize)) == 0)
-			exit(12);
+		if(filename) {
+			unsigned char buf[BUFSIZ];
+			unsigned long l,l1;
+			fd = open(filename,O_RDWR|O_TRUNC|O_CREAT,0644);
+			if(fd < 0) {
+				perror(filename);
+				exit(12);
+			}
+			for(l=0;l< fssize * sectorsize;l += l1) {
+				l1 = fssize * sectorsize;
+				if (BUFSIZ < l1)
+					l1 = BUFSIZ;
+				if (l1 != write(fd,buf,l1)) {
+					perror(filename);
+					exit(12);
+				}
+			}
+			membase = mmap(
+				0,
+				fssize * sectorsize,
+				PROT_READ|PROT_WRITE,
+				MAP_SHARED,
+				fd,
+				0);
+			if((int)membase == -1) {
+				perror("mmap");
+				exit(12);
+			}
+			close(fd);
+		} else {
+			if (fssize * sectorsize > memleft)
+				fssize = (memleft - 16384) / sectorsize;
+			if ((membase = malloc(fssize * sectorsize)) == 0)
+				exit(12);
+		}
 	}
 	fsi = fi;
 	fso = fo;
diff --git a/sbin/newfs/newfs.8 b/sbin/newfs/newfs.8
index 90be62daca7b..e342516bc048 100644
--- a/sbin/newfs/newfs.8
+++ b/sbin/newfs/newfs.8
@@ -42,7 +42,7 @@
 .Nm newfs
 .Op Fl NO
 .Op Fl S Ar sector-size
-.Op Fl a maxcontig
+.Op Fl a Ar maxcontig
 .Op Fl b Ar block-size
 .Op Fl c Ar cylinders
 .Op Fl d Ar rotdelay
@@ -62,7 +62,9 @@
 .Ar special
 .Nm mount_mfs
 .Op Fl N
-.Op Fl a maxcontig
+.Op Fl F Ar file
+.Op Fl T Ar disktype
+.Op Fl a Ar maxcontig
 .Op Fl b Ar block-size
 .Op Fl c Ar cylinders
 .Op Fl d Ar rotdelay
@@ -116,6 +118,14 @@ the file system has to be paged.
 .Pp
 The following options define the general layout policies.
 .Bl -tag -width Fl
+.It Fl T Ar disktype
+For backward compatibility and for
+.Nm mount_mfs .
+.It Fl F Ar file
+.Nm mount_mfs
+will use this file for the image of the filesystem.  When
+.Nm mount_mfs
+exits, this file will be left behind.
 .It Fl N
 Causes the file system parameters to be printed out
 without really creating the file system.
diff --git a/sbin/newfs/newfs.c b/sbin/newfs/newfs.c
index c419c302624f..88ee0736c1a5 100644
--- a/sbin/newfs/newfs.c
+++ b/sbin/newfs/newfs.c
@@ -180,6 +180,7 @@ int	sbsize = SBSIZE;	/* superblock size */
 int	mntflags = MNT_ASYNC;	/* flags to be passed to mount */
 u_long	memleft;		/* virtual memory available */
 caddr_t	membase;		/* start address of memory based filesystem */
+char	*filename;
 #ifdef COMPAT
 char	*disktype;
 int	unlabeled;
@@ -216,7 +217,7 @@ main(argc, argv)
 	}
 
 	opstring = mfs ?
-	    "NT:a:b:c:d:e:f:i:m:o:s:" :
+	    "NF:T:a:b:c:d:e:f:i:m:o:s:"
 	    "NOS:T:a:b:c:d:e:f:i:k:l:m:n:o:p:r:s:t:u:x:";
 	while ((ch = getopt(argc, argv, opstring)) != EOF)
 		switch (ch) {
@@ -235,6 +236,9 @@ main(argc, argv)
 			disktype = optarg;
 			break;
 #endif
+		case 'F':
+			filename = optarg;
+			break;
 		case 'a':
 			if ((maxcontig = atoi(optarg)) <= 0)
 				fatal("%s: bad maximum contiguous blocks\n",
@@ -530,6 +534,9 @@ main(argc, argv)
 		args.size = fssize * sectorsize;
 		if (mount(MOUNT_MFS, argv[1], mntflags, &args) < 0)
 			fatal("%s: %s", argv[1], strerror(errno));
+		if(filename) {
+			munmap(membase,fssize * sectorsize);
+		}
 	}
 #endif
 	exit(0);