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From: roberto@keltia.frmug.fr.net (Ollivier Robert)
Newsgroups: comp.os.386bsd.development
Subject: Re: PCFS on Hard Disks?
Date: 22 Jun 1994 08:54:09 +0200
Organization: A Happy FreeBSD-current Usenet Site
Lines: 290
Message-ID: <2u8n6v$8g@keltia.frmug.fr.net>
References: <2u5akn$i8l@cs.ubc.ca>
Reply-To: roberto@hsc.fr.net (Ollivier Robert)
NNTP-Posting-Host: keltia.frmug.fr.net
Mime-Version: 1.0
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Summary: Updated man page for pcfs
In article <2u5akn$i8l@cs.ubc.ca>, Terry Coatta <coatta@cs.ubc.ca> wrote:
>The man page for pcfs(5) states that PCFS support is only available for
>floppy drives. I've scanned over the archives for this newsgroup and
>haven't seen anything to indicate that this has changed and I am wondering
>if it is still the case? (I'm using 1.1-RELEASE)
No, it not the case any more. You can mount your primary DOS partition
providing that you have a label entry for it.
The file you mention is not a man page BTW. Here a corrected version
including support for hard disks. I send it to the FreeBSD list too.
BTW I think it should be somewhere else, maybe in man4/man4.i386.
[ This is my first attempt at nroff so please be kind :-) ]
------------------------------------------------------------
.\" Copyright 1994 Ollivier Robert (roberto@keltia.frmug.fr.net)
.\" All rights reserved.
.\"
.\" Based on previous pcfs.5 found in FreeBSD.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY ME ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL I BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $Id$
.\""
.Dd June 21, 1994
.Dt PCFS 5
.Os FreeBSD
.Sh NAME
.Nm pcfs
.Nd MS-DOS[TM] compatible filesystem
.Sh SYNOPSYS
Add the following statements to your configuration file in /sys/i386/conf/BLOT.
Or whatever you call your config file.
.Bd -literal
.Cd options PCFS
.Ed
.Pp
PCFS consumes approximately 24000 bytes of kernel code space and
approximately 4000 bytes of bss.
.Pp
.Sh DESCRIPTION
.Pp
The
.Nm
filesystem enables you to access of DOS floppy and hard
disks with UNIXcompatible semantics without having to resort to special
utilities such as
.Xr mdir 1
and
.Xr mcopy 1 .
.Pp
The
.Nm
filesystem should be considered as
.Em experimental
but it seems stable enough. We hope to integrate a better version in latter
versions of FreeBSD.
.Pp
.Sh OPERATIONAL DETAILS
.Em Floppy disks
.Pp
To mount a pcfs filesystem:
.Bd -literal
mount -t pcfs /dev/fd0a /mnt
.Ed
.Pp
To unmount a pcfs filesystem:
.Bd -literal
umount /mnt
.Ed
.Pp
If you want to be sure the fat is
.Nm ALWAYS
up to date, mount the filesystem with the synchronous option:
.Bd -literal
mount -t pcfs -o synchronous /dev/fd0a /mnt
.Ed
.Pp
This reasults in
.Nm very slow
file write performance because it turns off write behind of fst disk blocks.
.Pp
.Em Hard disks
.Pp
You must modify your current disk label (see
.Xr disklabel 5 )
to include a reference to your DOS partition.
.Pp
Assuming you'll use partition
.Dq Pa h ,
the last one, as your MS-DOS partition and that it is at the beginning of
the disk, you'll end with an entry like that in
.Em /etc/disktab
:
.Bd -literal
#
# Seagate ST-31200N
#
# a = / 12
# b = swap 32
# e = /usr/local 160
# f = /usr 55
# g = /spare 597
# h = /root/dos 150
#
st31200n|Seagate ST31200N 1 GB SCSI-2F:\\
:dt=SCSI:ty=winchester:\\
:nc#1006:ns#32:nt#64:se#512:rm#6300:\\
:oa#307200:pa#24576:ta=4.2BSD:ba#8192:fa#1024:\\
:ob#331776:pb#65536:tb=swap:\\
:oe#397312:pe#327680:te=4.2BSD:be#8192:fe#1024:\\
:of#724992:pf#112640:tf=4.2BSD:bf#8192:ff#1024:\\
:og#837632:pg#1222656:tg=4.2BSD:bg#8192:fg#1024:\\
:oh#32:ph#307168:th=MSDOS:
.Ed
.Pp
The DOS partition begins
.Em 32
sectors from the beginning of the disk (the first track of the first
cylinder is reserved for the partition table and other data). The type of
the partition (keyword
.Em th
) on the last line is set to MS-DOS.
.Pp
Run
.Xr disklabel 8
to install the new label.
.Pp
You must now decide whether you want to mount the partition at boot
time. If not, you
.Nm must
run the following command as
.Nm root
when you want to access the partition:
.Bd -literal
mount -t pcfs /dev/sd0h /dos
.Ed
.Pp
(replace /dos by your favorite mount point).
.Pp
If you want to mount it at boot time, you must include a statement into
your
.Dq Pa /etc/fstab
file (see
.Xr fstab 5 )
like that:
.Bd -literal
/dev/sd0h /root/dos pcfs rw 0 0
.Ed
.Pp
.Sh BUGS
This is the first release and as such has performance problems.
Reading large files is very slow because the read ahead code in pcfs_read()
doesn't read far enough ahead for filesystems with small blocksizes.
Performance and dos hard disk paritions are the next areas to be
worked on. Unless someone else does it.
.Pp
.Em PCFS quirks
.Pp
PCFS filesystems on floppy and hard disks are supported in this
release. You must add an entry in your disklabel for the DOS partition.
.Pp
Created files use only the user permissions bits. And of these
only the write bit is meaningful. DOS files always have the
execute and read bits on.
.Pp
PCFS does not turn on or off the DOS archive attribute bit.
.Pp
The timestamp on dos files is updated when ever the file is modified.
There is no inode time or create time stamp.
.Pp
The timestamp placed on a dos file does not have corrections for
daylight savings time included. It does have the correction for
timezone though.
.Pp
Unix times before 1980 will have their year set to 1980 in dos file
timestamps. This is because DOS's idea of time starts in 1980.
.Pp
PCFS filesystems do not support sparse files. Any attempt to seek
past the end of a file results in the blocks being allocated and
cleared.
.Pp
When
.Xr read 2
is used to examine pcfs directories you will get dos
directory contents. Note that the root directory does not contain
a "." or ".." entry. Only the
.Xr readdir 2
system call simulates these entries in the root directory of a dos
filesystem.
.Xr readdir 2
returns directory entries as described in
.Xr getdirentries 2 .
.Pp
Using
.Xr read 2
and
.Xr write 2
to manipulate the contents of dos directories
is unwise on an active DOS filesystem since a more up to date copy of
their contents may reside in data structures in the kernel. It is
probably safe to examine the filename field of dos directory entries.
The filesystem code keeps this up to date at all times.
.Pp
The cluster allocation algorithm is very simplistic. It starts at
cluster 2 and searchs until the last cluster of the filesystem and
takes the first available cluster.
.Pp
The
.Xr fsync 2
system call does not work on file descriptors open on
directories. This isn't a terrible thing since very few programs
open directories for writing.
.Pp
The PCFS filesystem truncates filenames quietly. If a filename has
more than 8 characters before the 1st period only the 1st eigth are
used. It only uses the 1st three characters after the period if
they exist. The filenames
.Dq Pa abc
and
.Dq Pa abc.
are the same to PCFS. Filenames that begin with a "." are considered to be
dos filenames with an extension only and so are limited to 3 characters
after the leading ".". For example
.Dq Pa .imlost
would be seen as
.Dq Pa .iml
by PCFS. PCFS folds filenames to upper case before writing them to disk or
looking up filenames, and folds them to lower case when reading them
from disk for presentation to the user (for example by
.Xr readdir 2 ).
.Pp
Directory entries for the DOS filesystem label are quietly ignored.
.Pp
This is probably going to be a problem. This implementation expects
the length of the root directory to be a multiple of the size of
a cluster. If this is not true a warning message is printed when
the filesystem is mounted.
.Pp
PCFS supports DOS filesystems with 12 bit or 16 bit FATs. It supports
both regular and huge filesystems ( > 32 megabytes). It supports
both version 3.3 and 5.0 BPB's. Don't know about version 4.x and
less than 3.3. It has not been tested with 16 bit fats or huge
filesystems. This is because the hard disk drivers need to support
dos partitions to do these things.
.Pp
PCFS does not support symbolic links or hard links. It does not
support quotas. How could it, pcfs files have no owners. PCFS
files have a simulated owner and group of 0. PCFS does not support
file locking. Though it may in the future. PCFS filesystems are
not remote mountable, but they will be in the future.
.Pp
PCFS has some debug printf's that can be turned on by defining PCFSDEBUG.
It produces lots of output. If you use it be sure to kill syslogd before
using a PCFS filesystem with debug.
.Sh SEE ALSO
.Xr disklabel 5 ,
.Xr disklabel 8 ,
.Xr fstab 5 ,
.Xr mount 8 .
.Sh HISTORY
A
.Nm
filesystem appeared in FreeBSD 1.0.
------------------------------------------------------------
--
Ollivier ROBERT roberto@hsc.fr.net
Hervé Schauer Consultants Ollivier.Robert@keltia.frmug.fr.net
PERL / MIME / PGP 2.6ui FreeBSD keltia 1.1.0(Current) CURRENT_137#0 i386