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[comp.unix.bsd] NetBSD, FreeBSD, and OpenBSD FAQ (Part 7 of 10)

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Posted-By: auto-faq
Archive-name: 386bsd-faq/part7

See reader questions & answers on this topic! - Help others by sharing your knowledge
Section 6.	(Interaction with MS-DOS)

6.0	Working with DOS and BNR/2 related software.

	This section is designed to cover some of the more common 
	problems that DOS will have when interacting with BNR/2.
	There are other sections of the FAQ that deal with 
	indirectly with this .  Try looking in sections 0, 1, and 2
	to see if something in there (particularly when talking 
	about DOS and *BSD coexisting on a single drive).

6.1	Formatting a floppy

	Formatting a floppy under NetBSD is possible through the the patch 
	file stored at 

	This patch appears to be for NetBSD 1.2 (release).  Obviously,
	use it at your own risk.

	FreeBSD (and I think OpenBSD) both have floppy formatting built
	into their systems in fairly recent versions.

6.2	Sharing the Disk with MS-DOS

	There are a myriad of questions about how to share a disk between
	*BSD and MS-DOS.  They all boils down to one of the <n> following

	1)  How can I partition my drive for both MS-DOS and *BSD?
	2)  I can install using the whole disk, but I can't install when 
	I try to share the drive between *BSD and MS-DOS.  Why?
	3)  I can use either MS-DOS or *BSD on my hard drive,
	but shutdown -todos doesn't seem to work.

6.2.1	How can I partition my drive to support both MS-DOS and *bsd?

	NOTE:  Before attempting to install *bsd on a computer with an
	active DOS partition, ALWAYS back up your hard drive.  No one on 
	the net, no matter how talented, can help you recover a hosed 
	MS-DOS file system.  If you lose all of your data, it is YOUR

	During the install phase, you need to have un-allocated space left
	on your disk drive.  This allows the install program to correctly
	install the *bsd partition in the partition table and DOS to
	peacefully co-exist with *bsd.

	If you do not have any space available on your hard drive, you will
	not be able to install both.  Re-fdisk your hard drive and make
	sure you have left un-allocated space in the partition table.  
	This WILL wipe out your DOS partition - Permanently.

	Even though the partition table procedure above may have worked, 
	there are still no guarantees that your system will boot after
	the install.  This problem most often manifests itself as one of
	the endless reboot problems.  You would normally be able to boot
	DOS from the hard disk, but not *bsd (once that partition is
	marked as active).

	Once the partition table has been correctly defined with both
	DOS and *bsd, there can still be problem.  One of the most
	common is that the disk drive works in some sort of translation
	mode.  This is particularly common with drives that physically have
	more than 1024 cylinders.  DOS cannot access a drive with more than
	1024 cylinders.  Translation mode will have to be turned off, usually
	by redefining your hard drive in SETUP as one of the user definable
	types.  This change will normally trash your hard drive, or at least
	render your DOS partition unreadable.

	The solution to this problem is to install *bsd at the end of the
	hard drive.  While DOS cannot use cylinders above 1024, *bsd has
	no such limitations, once it has booted.  During the boot-up phase,
	some of the newer boot blocks will refer to the BIOS for some
	services.  Specifically, the disk is checked for a bad sector map
	on the last track.  Since the BIOS cannot deal with cylinders
	higher than 1024, your bad sector map will be incorrectly
	identified as 1023 if the number of cylinders is larger than that.
	This problem is being worked on, and I hope to change this section
	with better news later.

	NOTE:  The only people that this problem will effect are those 
	MFM and ESDI users that have drives with more than 1023 tracks.  
	While drives of this type are not the overwhelming majority, 
	neither are they an anomaly.  People are working on it.

	As an example, if your hard disk physically has 8 heads, 16 sectors 
	per track, and 2000 cylinders (128M); you MUST use some sort of disk
	translation in order to use the entire drive.  An obvious geometry
	for this drive (for DOS) would be 16 heads, 16 sectors, and 1000
	cylinders.  Unfortunately, *bsd operates using the disk drives
	native geometry as reported during the probe phase of boot up.  This
	will probably be 8/16/2000, and will NOT agree with your translated
	disk geometry.  This causes an endless reboot cycle.  If you change
	the geometry so that the drive agrees with the disklabel, your DOS
	partition is toast.

	The best way to operate in this case would be to (for example)
	split the disk in half.  That leaves 64M for DOS, using a 
	geometry of 8 heads, 16 sectors per track, and the first 1000 
	cylinders for DOS.  The second 1000 cylinders could then safely
	be used for *bsd.  The DOS partition table may even be capable of
	showing this partition as it actually exists.


	First off, it's important to understand BSD disklabels.  The 
	disklabel is a description of the Unix partition layout and other 
	disk parameters stored on-disk, usually somewhere in the first 
	couple of sectors.  There is a maximum of 8 partitions, labelled 
	"a" thru "h".  Typically partition "a" is assigned to the root 
	partition, partition "b" is configured as a swap area, and 
	partition "c" is defined as the whole disk.  You can change these, 
	but it's a good idea to stick with this scheme, as many programs 
	assume that's the way things are going to be.

	If you're whole disk is dedicated to Unix, then that's all you 
	need to know.  But if you're sharing your disk with DOS, then 
	there are a few magical things happening.

	DOS has it's own partitioning scheme.  The way NetBSD co-exists 
	with this is to fit all of the Unix partitions into one DOS 
	partition.  So partitions a-h all fit inside one DOS partition, 
	which has a partition type of 165 (each MS-DOS partition has a 
	"partition type" associated with it.  The BSD partition type is 
	165).  In this setup, partition "c" refers to the entire BSD 
	partition.  But in this scheme, partition "d" refers to the ENTIRE 
	disk, MS-DOS partitions and all.

	So, if you want to access your MS-DOS partition from NetBSD, first 
	you'll have to create a partition that points to the MS-DOS 
	partition.  You'll want to run the command:

	disklabel -e -r /dev/r??0d	(fill in with your disk type).

	You'll get popped into an editor with all the disklabel stuff in 
	it.  Go down to the bottom.  You should see something like:

	6 partitions:
	#        size   offset    fstype   [fsize bsize   cpg]
  	a:    30720   409600    4.2BSD     1024  8192    16   # (Cyl...
  	b:   129024   440320      swap                        # (Cyl...
  	c:  1617920   409600    unused        0     0         # (Cyl...
  	d:  2029568        0    unused        0     0         # (Cyl...
  	e:    61440   569344    4.2BSD     1024  8192    16   # (Cyl...
  	f:  1396736   630784    4.2BSD     1024  8192    16   # (Cyl...
	(or whatever it appropriate for your disk).  Note that partition 
	"a" starts on cylinder 200.  That's where my BSD partition starts 
	on my disk.  Also note that partition "c" starts at 200 as well 
	and goes to the end of the disk.  You'll also note that partition 
	"d" goes from sector 0 all the way to the end of the disk.
	Add a new line that looks something like:
  	g:   409568       32    MS-DOS                  # (Cyl.    0*- 199*)
	(The comment on the end isn't necessary.  Only the partition 
	letter, size, offset, and partition type are needed.  You can 
	put unused in instead of MS-DOS if you want).
	*NOTE* Be sure to change the line that says "6 partitions" to the 
	new number of partitions that you have!!!  Otherwise you'll get an 
	obscure error.  In my case I'd change that line to be "7 partitions".  
	If you aren't sure what your MS-DOS partition size and offsets are, 
	you can use the NetBSD fdisk to find them out.  Don't forget that 
	there's a maximum of 8 partitions.  

	Once you do that and you have MSDOSFS configured into your kernel, 
	you can just do something like "mount -t msdos /dev/sd0g /msdos".  
	Or you can put a line like this in your fstab:
	/dev/sd0g /msdos msdos rw 0 0
	If you want to access a DOS-only HD from NetBSD, here are some 
	instructions posted by Charles Hannum a while back.  I haven't 
	tried them myself, but they seem like they would work.
	Assuming you don't have something (like OS-BS) which uses the extra
	sectors in the boot track, you can do the following:

	1) Use the NetBSD `fdisk' or DOS `pfdisk' to create a NetBSD 
	partition in the MBR which spans the entire disk.

	2) Save a copy of the MBR:

		dd if=/dev/rsd0d of=my-mbr bs=1b count=1

	3) Use `disklabel' to create a NetBSD label with the DOS partition 
	and whatnot.  Answer `y' when it asks you if you want to `overwrite 
	[a] disk with [a] DOS partition table'.

	4) Put back the saved copy of the MBR:

		dd if=my-mbr of=/dev/rsd0d bs=1b count=1

	This works for me.  Your mileage may vary.

	Luke Mewburn <> has provided the following tutorial on 
	using the pfdisk program and making your *bsd/NetBSD partitions
	peacefully coexist with DOS.  While this is kind of a 'cookbook' 
	approach, please keep in mind that this is probably easily 
	transferable to all BNR derived Unices.

6.2.2	I can install using the whole disk, but I can't install when 
	I try to share the drive between *BSD and MS-DOS.  Why?

	This is an extension of the question above.  The most common 
	reason for this is, once again, disk translation problems.  If 
	the disklabel does not agree with the disk geometry, the install 
	will fail.  Other incarnations of this problem are that you can 
	install DOS, then *BSD, and DOS will be hosed, or vice versa.

	There are more than a couple of people who will blithely suggest 
	that this is a good thing, and you should install *BSD exclusively,
	job not withstanding.

6.2.4	Is there any hope of ever running MS-DOS applications under any of
	the free BSD systems?

	There is currently a project in development to port the Windows 
	program environment to Linux and the *BSD systems.  Here is an
	excerpt from the original message announcing the project:

	As many of you already know, we are in the process of creating a
	Windows emulator.  This emulator is similar to Sun's Wabi product, 
	but is being developed completely independent of them.  Many of 
	you are anxious to hear the latest status of the project.  I have 
	created a mailing list for those of you.  To join the list, simply 
	send mail to:

	If your mailing address is not easy to deduce from the mail 
	headers, then place the following line in the body of the message 
	that you send.

	Reply-To: youraddress@yourmachine

	where youraddress@yourmachine should be replaced by your actual 
	mailing address.

6.2.5	How do I get Linux executables to run under NetBSD?

	First, you need to make certain your kernel has LINUX_COMPAT as
	one of the options for your kernel.  Second, you will need the
	libraries for Linux.  You can find the Linux supporting binaries 
	for NetBSD i386 at  There
	are instructions there to tell you how to get the libraries
	working correctly.  

	With VERY new versions of NetBSD (NetBSD 1.3A and above) the
	kernel option for Linux compatibility have changed.  All ELF and
	COFF executables, as well as native Linux executables will be
	included as part of the same option.

6.3	Accessing the MS-DOS filesystem 

	One of the most common MS-DOS related questions (with the possible
	exception of 6.2 above) is how to access the DOS disk partitions
	from *BSD.  

		How to mount your DOS partition from FreeBSD

	1. First, be root.  The following won't work as an ordinary user.

	2. Second, use 'fdisk' to see where your DOS partition starts.  
	It will be labeled as type DOS.  On my system, 'fdisk /dev/sd0d' 
	produces the following:

		... (extraneous output, not of interest) ...
	The data for partition 0 is:
	sysid 6,(Primary 'big' DOS (> 32MB))
	    start 32, size 306400 (149 Meg), flag 0
	        beg: cyl 0/ sector 1/ head 1;
	        end: cyl 149/ sector 32/ head 39

	    This shows me that my DOS partition starts at sector 32, and 
	is 306400 (512 byte) sectors long.

	NOTE:  If you're trying to mount a DOS `EXTENDED' partition, then 
	you need to add the number of sectors per track to this start 
	address you got from fdisk in subsequent calculations, I.E. in 
	the above example (assuming it was an EXTENDED partition rather 
	than the Primary), you'd use `start 64, size 306400'.

	[Ed.Note.  This example assumes a SCSI disk.  For disks with a 
	number of sectors per track which is different than 32, you will
	probably see the 32s above replaced with your number of sectors
	per track. IDE, MFM, and ESDI drives are all examples where the
	number of sectors per track is likely to NOT be 32.]

	3. Next, using this information, you craft a new disk entry in your
	   /etc/disktab file that assigns one of your unused "UNIX" 
	   partitions to this DOS region.  Again, using my system as a 
	   default, you see I've created:

	disk0|DEC 5501:\

	   As you can see, partition 'e' now points to the DOS partition as
	   pointed out by fdisk.

	   [Ed.Note again.  Remember what I said about the 32 above...]
	   Also, there may be a problem with some versions of disklabel
	   not recognizing the MSDOS (or MS-DOS, depending) in the te:
	   entry above.  You may need to run a "disklabel -e" to get the
	   partition type to 'stick'. 

	4. Now we have to actually stick the label on the disk, which is done
	   with disklabel.  Using my example, this would be:

	    disklabel -r -w sd0 disk0 SCSI /usr/mdec/sdboot /usr/mdec/bootsd

	5. Reboot your system to see the new disk label.

	6. Mount the DOS partition.  I do:

		mount -t pcfs /dev/sd0e /dos_c

	   Where /dos_c is just a convenient directory to mount it.

	7. You're set!

	With the exception that the '-t' option is msdos in NetBSD, these 
	instructions seem to work with the same facility for NetBSD.  I
	also received a note a couple of weeks ago (that I promptly deleted
	because I new that I would remember what it said) that DOS extended
	partitions are readable if you skip the first 'n' blocks in your 
	computations (where 'n' is your number of sectors per track).  This 
	way, you skip over the 'new' part of the DOS file system.  That means 
	that instead of the oe:32 above, you would need an oe:48 instead.  

	Also remember that the compressed file system in DOS 6 will probably
	be completely Greek to your NetBSD/FreeBSD system.  I seriously 
	doubt that you will be able to read the compressed DOS file system
	anytime in the foreseeable future.

6.4	NFS/PC-NFS support

	The problems normally associated with PC-NFS are also associated 
	with NFS in general.  

6.4.1	Can I use 8K packets for NFS?  When I try, I have all kinds of 
	problems.  Specifically, I get 'ring buffer overflows' or the
	performance is real bad.

	In addition to the NE2000 card, this problem can also manifest 
	itself on other ISA networks cards that have a limited amount of
	memory.  Ken Raeburn ( has identified 
	a common problem with the NE2000 card and provided us with a work

	I reported previously that I was seeing problems reading files over
	NFS using the NE2000 driver; timeouts would eventually be reported, no
	data would be read.  Listing files and directories (small ones
	anyway) were not a problem.

	In the meantime, mounting NFS file systems with "rsize=1024" does get
	rid of this problem.


	As a matter of policy, specifying "rsize=1024,wsize=1024" works 
	very well also, and makes the transfers seem to run faster.  This 
	is probably because there are fewer collisions.  The disadvantage 
	of this method comes from the kernel 'sync'ing after all NFS 
	writes.  This can slow NFS accesses considerably.  As with most 
	generalizations, this one too can do nearly as much harm as good.  
	If you have trouble, reduce your default packet size until the 
	problem goes away.

	With the newer drivers (especially the ed driver) most of these 
	problems are solved automagically.  If you are still using the
	original 386bsd 0.1 release, you REALLY need to upgrade.
	See section 6.4.5 on 'ring buffer overflows' and the 3C503 for
	more discussion on this problem.

6.4.2	How do I get around the NFS "Permission denied" error?

	The problem is not the configuration of the server (unless there is
	no real requirement to run it in "secure" mode, and you happen to
	be running it that way anyway).  The problem is the fact that,
	even though mount request are sent on a privileged port, NFS
	connections are not.

6.4.3	What does the message "BAD MNT RPC: RPC Authentication error; 
	why = Invalid client credential" mean when I try to mount something
	from another machine?

	Hellmuth Michaelis ( offers the solution to this
	relatively common problem:

	You have to make sure that the user "root" is not present in more
	than 8 entries in the "/etc/group" - file on the *BSD machine.
	Simply remove some entries and the NFS mounts will succeed.  

6.4.4	What does the message "Bad MNT RPC: RPC: Authentication error; 
	why = Client credential too weak" mean when I try to mount something
	from another machine?

	This problem is a standard NFS problem; it simply means that your 
	user number is not one of the ones that can mount this NFS.  
	Normally, you will get this message when you are trying to mount 
	a filesystem from a machine that allows 'root' to mount an NFS,
	but limits other users.

	Another documented problem with "client credentials being too
	weak" is the dichotomy of SunOS and 4.4 based systems.  SunOS,
	and other commercial systems, do not allow NFS commands to come
	in on anything but a reserved port.  There are several places
	that need to be addressed if weak credentials are a problem.
	The first is the mount command.  The mount itself may work, but
	all references to files in the NFS will fail.  This is usually
	the most common symptom of this problem.  The solution for this
	is to either include the '-o resvport' keyword pair on the mount
	command, or the -P option.  In addition to the resvport command
	on the mount, it may become important to include an NFS volume
	in your fstab.  If this is the case, you will need to ensure
	that the resvport keyword is added on the mount line in the
	fstab.  Finally, if you are using the automounter, you will need
	to make absolutely certain that you have included the resvport
	option in your automount maps as the default.

6.4.5	I get a lot of 'ring buffer overflow' messages using NFS and the
	ed0 driver.  Is there a problem?

	David Greenman (, the original author of 
	the ed0 driver, provides us with some insight into the inner 
	workings of the ed0 driver.

	   It always surprises me that people don't just ask the original 
	author these questions. :-) Anyway, the reason these are happening 
	is that the access to the 8bit boards shared memory simply isn't 
	fast enough to deal with full wire speeds...but the driver tries even though packets get dropped, your performance only 
	drops to about what the ethernet board is capable of (should be 
	in the 400-600k range with an 8bit card). NFS is especially bad 
	because the UDP window is quite large (40k last time I looked), 
	so the overflow condition can happen easily. I've explained this
	for the most part in the release notes for the driver, but these 
	didn't make it into either the FreeBSD or NetBSD releases (we 
	couldn't find an appropriate place to put them).

	>From the release notes:

	   The 8390 implements a shared memory ring-buffer to store 
	incoming packets.  The 8bit boards (3c503, and 8003) usually have 
	only 8k bytes of shared memory.  This is only enough room for about 
	4 full size (1500 byte) packets. This can sometimes be a problem, 
	especially on the original WD8003E and 3c503.  This is because these 
	boards' shared memory access speed is also quite slow compared to 
	newer boards - typically only about 1MB/second. The additional 
	overhead of this slow memory access, and the fact that there is 
	only room for 4 full-sized packets means that the ring-buffer 
	will occasionally overflow.  When this happens, the board must 
	be reset to avoid a lockup problem in early revision 8390's.  
	Resetting the board will cause all of the data in the ring-buffer 
	to be lost - requiring it to be re-transmitted/received...slowing 
	things even further.  Because of these problems, maximum throughput 
	on boards of this type is only about 400-600k per second. The 16bit 
	boards (8013 series), however, have 16k of memory as well as much 
	faster memory access speed. Typical memory access speed on these 
	boards is about 4MB/second. These boards generally have no problems 
	keeping up with full ethernet speed. The only problem I've seen 
	with these boards is related to the (slow) performance of the
	system's malloc code when additional mbufs must be added to the 
	pool. This can sometimes increase the total time to remove a 
	packet enough for a ring-buffer overflow to occur.  

	With NFS, the problem is really bad, though.  The 3c503 does not 
	have enough memory on the card to support the default 8k packets 
	that NFS and other protocols use as their default.  The solution 
	for folks that are having a problem with ring buffer overflows 
	in NFS is for them to either use the -r and -w flags to limit 
	the packet size or use the define "NFS_BOOT_RWSIZE=8192".  If 
	NFS doesn't work with this defined, the code will automatically 
	step down to the next smaller increment.  If you KNOW that you 
	will always be running a 3c503, you can set this define to 4096 
	instead, just to make sure.  This should eliminate the bulk of 
	the ring buffer overflows in NFS.

6.4.6	I am getting really poor performance out of my network,
	especially when talking to older networks or when performing
	short file transfers.  What's the problem?

	Try turning off rfc1323 support:

		sysctl w net.inet.tcp.rfc1323=0

	only in newer builds. In older versions you have to edit a kernel 
	config file.  RFC1323 is not yet supported by all networks, and
	can cause TCP performance degradation when tried.  This, for
	example, is a known problem on older Sun and VAX hosted
	networks, and on many networks which are using Linux as an
	intermediate host.

6.4.7	Is there any PC software that will allow me to use my enormous PC
	with all of the unsupported hardware as a PC-NFS server?

	Yes.  It is called SOSS, and is available from MANY FTP sources.
	You will need the aforementioned Clarkson Packet Drivers for it
	to work, but that shouldn't cause too many problems for most 

6.5	How can I use mtools with the 'new' floppy naming convention?

	With the adoption of BSD 4.4, there is a new way of accessing
	the floppy disk drive types.  The method uses the minor device
	number to specify different media sizes and densities.  These
	densities are established by a table from the file 
	/usr/src/sys/arch/i386/isa/fd.c in NetBSD (your mileage may
	vary).  The table in FreeBSD's fd.c is likely to be slightly

	The order of the entries defines the order of the minor
	numbers, so the table below has the following characteristics:

	    /dev/fd0a	0	/* default disk type */
 	    /dev/fd0b	1	/* 1.44MB diskette */ 
	    /dev/fd0c	2	/* 1.2 MB AT-diskettes */ 
	    /dev/fd0d	3	/* 360KB in 1.2MB drive */ 
	    /dev/fd0e	4	/* 360KB PC diskettes */ 
	    /dev/fd0f	5	/* 3.5" 720KB diskette */ 
	    /dev/fd0g	6	/* 720KB in 1.2MB drive */ 
	    /dev/fd0h	7	/* 360KB in 720KB drive */

	struct fd_type fd_types[] = {
        	{ 18,2,0xff,0xcf,0x1b,0x6c,80,2880,1,FDC_500KBPS,2,"1.44MB"  },
        	{ 15,2,0xff,0xdf,0x1b,0x54,80,2400,1,FDC_500KBPS,2,"1.2MB"   },
        	{  9,2,0xff,0xdf,0x23,0x50,40, 720,2,FDC_300KBPS,2,"360KB/AT"},
        	{  9,2,0xff,0xdf,0x2a,0x50,40, 720,1,FDC_250KBPS,2,"360KB/PC"},
        	{  9,2,0xff,0xdf,0x2a,0x50,80,1440,1,FDC_250KBPS,2,"720KB"   },
        	{  9,2,0xff,0xdf,0x23,0x50,80,1440,1,FDC_300KBPS,2,"720KB/x" },
        	{  9,2,0xff,0xdf,0x2a,0x50,40, 720,2,FDC_250KBPS,2,"360KB/x" },

	In order to add a new device (such as a 2.44 Meg floppy) new
	tables entries are theoretically all that would be needed.  As
	new entries are created, the minor device numbers would
	increase and the associated device names would be added.
Dave Burgess                   Network Engineer - Nebraska On-Ramp, Inc.
*bsd FAQ Maintainer / SysAdmin for the NetBSD system in my spare bedroom
"Just because something is stupid doesn't mean there isn't someone that 
doesn't want to do it...."

User Contributions:

Apr 12, 2022 @ 11:11 am
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