DOSSRV(4)DOSSRV(4)NAME
dossrv, 9660srv, a:, b:, c:, d:, 9fat:, dosmnt, eject - DOS and ISO9660
file systems
SYNOPSISdossrv [ -rsv ] [ -f file ] [ service ]
9660srv [ -9Jsv ] [ -c clusters ] [ -f file ] [ service ]
a:
b:
c:
9fat:
dosmnt n mtpt
eject [ n ]
DESCRIPTION
Dossrv is a file server that interprets DOS file systems. A single
instance of dossrv can provide access to multiple DOS disks simultane‐
ously.
Dossrv posts a file descriptor named service (default dos) in the /srv
directory. To access the DOS file system on a device, use mount with
the spec argument (see bind(1)) the name of the file holding raw DOS
file system, typically the disk. If spec is undefined in the mount,
dossrv will use file as the default name for the device holding the DOS
system.
Normally dossrv creates a pipe to act as the communications channel
between itself and its clients. The -s flag instructs 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 /srv.
The -v flag causes verbose output for debugging, while the -r flag
makes the file system read-only.
The shell script a: contains
unmount /n/a: >[2] /dev/null
mount -c /srv/dos /n/a: /dev/fd0disk
and is therefore a shorthand for mounting a floppy disk in drive A.
The scripts b: and dosmnt are similar, mounting the second floppy disk
and the nth non-floppy DOS partition, respectively. C: and d: call
dosmnt in an attempt to name the drives in the same order that Micro‐
soft operating systems do. 9fat: provides access to the FAT component
of the Plan 9 partition (see prep(8)).
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 wstat (see 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 corre‐
sponds to setting the read-only attribute in the DOS file system. Most
of the other DOS attributes are not accessible.
Setting the exclusive use flag (DMEXCL) in Plan 9 corresponds to set‐
ting the system use attribute in the DOS file system. Such files are
not actually restricted to exclusive use, but do merit special treat‐
ment that helps in the creation of boot disks: when 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.
Since other operating systems do not guarantee that system files are
laid out contiguously, the DMAPPEND mode bit is set in file stat infor‐
mation only when the file is currently contiguous. Attempts to set the
DMAPPEND mode bit explicitly will cause dossrv to try to make the file
contiguous, succeeding only if this is possible.
9660srv is similar to dossrv in specification, except that it inter‐
prets ISO9660 CD-ROM file systems instead of DOS file systems. Some
CDs contain multiple directory trees describing the same set of files.
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 -9 flag causes
9660srv to ignore the Plan 9 system use fields, while the -J flag
causes it to ignore the Joliet tree. The -c option sets the size of
the RAM cache to clusters clusters of 128KB. The default clusters is
16, but a value of 5600 will cache an entire CD incrementally.
If the floppy drive has an ejection motor, eject will spit out the
floppy from drive n, default 0.
EXAMPLE
Mount a floppy disk with a DOS file system on it.
a:
SEE ALSOkfs(4)SOURCE
/sys/src/cmd/dossrv
/sys/src/cmd/9660srv
/rc/bin/eject
BUGS
The overloading of the semantics of the DMEXCL and DMAPPEND bits can be
confusing.
DOSSRV(4)
