.TH DOSSRV 4
.SH NAME
dossrv, 9660srv, a:, b:, c:, d:, 9fat:, dosmnt, eject \- DOS and ISO9660 file systems
.SH SYNOPSIS
.B dossrv
[
.B -rsv
] [
.B -f
.I file
] [
.I service
]
.PP
.B 9660srv
[
.B -9Jsv
] [
.B -c
.I clusters
] [
.B -f
.I file
] [
.I service
]
.PP
.B a:
.PP
.B b:
.PP
.B c:
.PP
.B 9fat:
.PP
.B dosmnt
.I n
.I mtpt
.PP
.B eject
[
.I n
]
.SH DESCRIPTION
.I Dossrv
is a file server that interprets DOS file systems.
A single instance of
.I dossrv
can provide access to multiple DOS disks simultaneously.
.PP
.I Dossrv
posts a file descriptor named
.I service
(default
.BR dos )
in the
.B /srv
directory.
To access the DOS file system on a device, use
.B mount
with the
.I spec
argument
(see
.IR bind (1))
the name of the file holding raw DOS file system, typically the disk.
If
.I spec
is undefined in the
.BR mount ,
.I dossrv
will use
.I file
as the default name for the device holding the DOS system.
.PP
Normally
.I dossrv
creates a pipe to act as the communications channel between
itself and its clients.
The
.B -s
flag instructs
.I dossrv
to use its standard input and output instead.
The kernels use this option if they are booting from a DOS disk.
This flag also prevents the creation of an explicit service file in
.BR /srv .
.PP
The
.B -v
flag causes verbose output for debugging, while
the
.B -r
flag makes the file system read-only.
.PP
The shell script
.I a:
contains
.IP
.EX
unmount /n/a: >[2] /dev/null
mount -c /srv/dos /n/a: /dev/fd0disk
.EE
.LP
and is therefore a shorthand for mounting a floppy disk in drive A.
The scripts
.I b:
and
.I dosmnt
are similar,
mounting the second floppy disk
and the
.IR n th
non-floppy DOS partition,
respectively.
.I C:
and
.I d:
call
.I dosmnt
in an attempt to name the drives in
the same order that Microsoft operating systems do.
.I 9fat:
provides access to the FAT component of the Plan 9 partition (see
.IR prep (8)).
.PP
The file attribute flags used by the DOS file system
do not map directly to those used by Plan 9.
Since there is no concept of user or group,
permission changes via
.B wstat
(see
.IR stat (2))
will fail unless the same (read, write, execute) permissions
are specified for user, group, and other.
For example, removing write permission in Plan 9
corresponds to setting the read-only
attribute in the DOS file system.
Most of the other DOS attributes
are not accessible.
.PP
Setting the exclusive use flag (DMEXCL)
in Plan 9 corresponds to setting the
system use attribute in the DOS file system.
Such files are not actually restricted to exclusive use,
but do merit special treatment that
helps in the creation of boot disks:
when 
.I dossrv
allocates a new block for such a file
(caused, say, by a write that fills the file's
last allocated block), it succeeds only if it can
arrange for the file to be stored
contiguously on disk.
.PP
Since other operating systems do not
guarantee that system files are laid
out contiguously, the DMAPPEND mode
bit is set in file stat information
only when the file is currently contiguous.
Attempts to set the DMAPPEND mode bit
explicitly will cause 
.I dossrv
to try to make the file contiguous,
succeeding only if this is possible.
.PP
.I 9660srv
is similar to
.I dossrv
in specification, except that it interprets ISO9660 CD-ROM
file systems instead of DOS file systems.
Some CDs contain multiple directory trees describing
the same set of files.
.IR 9660srv 's
first choice in such a case is a standard ISO9660 tree
with Plan 9 system use fields;
the second choice is a Microsoft ``Joliet'' tree, which
allows long file names and Unicode characters;
the third choice is a standard ISO9660 or High Sierra tree.
The
.B -9
flag causes
.I 9660srv
to ignore the Plan 9 system use fields,
while the
.B -J
flag causes it to
ignore the Joliet tree.
The
.B -c
option sets the size of the RAM cache to
.I clusters
clusters of 128KB.
The default
.I clusters
is 16,
but a value of 5600 will cache an entire CD incrementally.
.PP
If the floppy drive has an ejection motor,
.I eject
will spit out the floppy from drive
.IR n ,
default 0.
.SH EXAMPLE
Mount a floppy disk with a DOS file system on it.
.IP
.EX
a:
.EE
.SH "SEE ALSO"
.IR kfs (4)
.SH SOURCE
.B /sys/src/cmd/dossrv
.br
.B /sys/src/cmd/9660srv
.br
.B /rc/bin/eject
.SH BUGS
The overloading of the semantics of
the DMEXCL and DMAPPEND
bits can be confusing.