.\" Copyright (c) 2002
.\"	Nate Lawson.  All rights reserved.
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.Dd November 15, 2002
.Dt SCSI_TARGET 8
.Os
.Sh NAME
.Nm scsi_target
.Nd usermode SCSI disk emulator
.Sh SYNOPSIS
.Nm
.Op Fl AdST
.Op Fl b Ar size
.Op Fl c Ar size
.Op Fl s Ar size
.Op Fl W Ar num
.Ar bus : Ns Ar target : Ns Ar lun
.Ar filename
.Sh DESCRIPTION
The
.Nm
utility emulates a SCSI target device using the
.Xr targ 4
device driver.
It supports the basic commands of a direct access device, like
.Xr da 4 .
In typical operation, it opens a control device and
enables target mode for the specified LUN.
It then communicates with
the SIM using CCBs exchanged via
.Xr read 2
and
.Xr write 2 .
READ and WRITE CDBs are satisfied with the specified backing store file.
.Pp
For performance, all backing store accesses use
.Xr aio 4 .
Thus,
.Nm
requires a kernel compiled with
.Cd "options VFS_AIO" .
.Pp
Options:
.Bl -tag -width indent
.It Fl A
Enable 16 addresses if supported by the SIM.
Default is 8.
.It Fl S
Enable synchronous transfers if supported by the SIM.
Default is disabled.
.It Fl T
Enable tagged queuing if supported by the SIM.
Default is no tagged queuing.
.It Fl W Cm 8 | 16 | 32
Enable 16 or 32 bit wide transfers if supported by the SIM.
Default is 8.
.It Fl b Ar bufsize
Set buffer size for transfers.
Transfers larger than this will be split into multiple transfers.
.It Fl c Ar sectorsize
Set sector size for emulated volume.
Default is 512.
.It Fl d
Enable debugging output in
.Nm
and its associated control device.
.It Fl s Ar volsize
Use a different size for the emulated volume.
Must be less than or equal to the size of
.Ar filename .
If the number ends with a
.Dq Li k ,
.Dq Li m ,
.Dq Li g ,
.Dq Li t ,
.Dq Li p ,
or
.Dq Li e ,
the number is multiplied by 2^10 (1K), 2^20 (1M), 2^30 (1G), 2^40 (1T),
2^50 (1P) and 2^60 (1E)
respectively.
.El
.Pp
Required arguments:
.Bl -tag -width indent
.It Ar bus : Ns Ar target : Ns Ar lun
Attach to specified bus ID, target ID, and LUN.
.It Ar filename
File to use as a backing store.
.El
.Pp
All options default to the minimal functionality of SCSI-1.
To be safe,
.Nm
checks the SIM for the requested capability before enabling target mode.
.Sh FILES
.Bl -tag -width ".Pa /usr/share/examples/scsi_target" -compact
.It Pa /dev/targ*
Control devices.
.It Pa /usr/share/examples/scsi_target
Source directory.
.El
.Sh EXAMPLES
Create a 5 megabyte backing store file.
.Pp
.Dl "dd if=/dev/zero of=vol size=1m count=5"
.Pp
Enable target mode on bus 0, target ID 1, LUN 0, using
.Pa vol
as the backing store for READ6/10 and WRITE6/10 commands.
Only the first 1000 bytes of
.Pa vol
will be used.
Debugging information will be output.
16-bit wide transfers will be used if the SIM supports them.
.Pp
.Dl "scsi_target -d -s 1000 -W 16 0:1:0 vol"
.Sh SEE ALSO
.Xr scsi 4 ,
.Xr targ 4
.Sh AUTHORS
.An -nosplit
The
.Nm
example first appeared in
.Fx 3.0
and was written by
.An Justin T. Gibbs .
It was rewritten for
.Fx 5.0
by
.An Nate Lawson Aq Mt nate@root.org .