term% cat index.txt SCUZZ(8) System Manager's Manual SCUZZ(8)
NAME
scuzz - SCSI target control
SYNOPSIS
scuzz [ -6eq ] [ -m max-xfer ] [ [ -r ] sddev ]
DESCRIPTION
Scuzz is an interactive program for exercising raw SCSI devices. Its
intended purpose is to investigate and manipulate odd devices without
the effort of writing a special driver, such as shuffling the media
around on an optical jukebox. It reads commands from standard input
and applies them to a SCSI target (other devices accessed through the
sd(3) interface, such as ATA(PI) devices, may also work). If sddev is
given on the command line, an open (see below) is immediately applied
to the target. On successful completion of a command, ok n is printed,
where n is the number of bytes transferred to/from the target; the -q
command line option suppresses the ok message.
The -6 forces the use of 6-byte SCSI commands rather than 10-byte ones.
Some older devices require this, though scuzz attempts to adapt auto‐
matically. The -e makes scuzz more willing to retry I/O errors but
less tolerant of other errors and implies -6. This option is often
needed to read Exabyte 8mm tapes. The -m option sets the maximum I/O
transfer size to max-xfer. Exabyte drives often require this to be
1024 or the exact tape block size and some 4mm drives require this to
be the exact tape block size or larger.
Commands
help command
Help is rudimentary and prints a one line synopsis for the named
command, or for all commands if no argument is given.
probe Probe attempts an inquiry command on all SCSI units, and prints
the result preceded by the name of those targets which respond.
The help and probe commands may be given at any time.
open [-r]sddev
Open must be given before any of the remaining commands will be
accepted. Internally, unless the -r option is given, open is‐
sues ready then inquiry, followed by a device class-specific
command to determine the logical block size of the target. Sd‐
dev is an sd(3) device directory like /dev/sdC0.
close Close need only be given if another target is to be opened in
the current session.
The remaining commands are in rough groups, intended for specific
classes of device. With the exception of the read, write, and space
commands, all arguments are in the style of ANSI-C integer constants.
ready Test Unit Ready checks if the unit is powered up and ready to do
read and write commands.
rezero Rezero Unit requests that a disk be brought to a known state,
usually by seeking to track zero.
rewind Rewind positions a tape at the beginning of current partition
(there is usually only one partition, the beginning of tape).
reqsense
Request Sense retrieves Sense Data concerning an error or other
condition and is usually issued following the completion of a
command that had check-condition status. Scuzz automatically
issues a reqsense in response to a check-condition status and
prints the result.
format Format Unit performs a ``low level'' format of a disk.
rblimits
Read Block Limits reports the possible block lengths for the
logical unit. Tapes only.
read file nbytes
Read transfers data from the target to the host. A missing
nbytes causes the entire device to be read.
write file nbytes
Write transfers data from the host to the target. A missing
nbytes causes the entire input file to be transferred.
The first argument to the read and write commands specifies a
source (write) or destination (read) for the I/O. The argument
is either a plain file name or | followed by a command to be ex‐
ecuted by rc(1). The argument may be quoted in the style of
rc(1).
seek offset whence
Seek requests the target to seek to a position on a disk, argu‐
ments being in the style of seek(2); whence is 0 by default.
Scuzz maintains an internal notion of where the current target
is positioned. The seek, read, write, rewind, rezero, and
wtrack commands all manipulate the internal offset.
filemark howmany
Write Filemarks writes one (default) or more filemarks on a
tape.
space [-b] [-f] [[--]howmany]
Space positions a tape forwards or backwards. The arguments
specify logical block (-b) or filemark (-f) spacing; default is
-b. If howmany is negative it specifies spacing backwards, and
should be preceded by -- to turn off any further option process‐
ing. Default is 1.
inquiry
Inquiry is issued to determine the device type of a particular
target, and to determine some basic information about the imple‐
mented options and the product name.
modeselectbytes...
modeselect6bytes...
Mode Select is issued to set variable parameters in the target.
Bytes given as arguments comprise all the data for the target;
see an appropriate manual for the format. The default is the
10-byte form of the command; modeselect6 is the 6-byte version.
modesense [page[nbytes]]
modesense6 [page[nbytes]]
Mode Sense reports variable and fixed parameters from the tar‐
get. If no page is given, all pages are returned. Nbytes spec‐
ifies how many bytes should be returned. The default is the
10-byte form of the command; modesense6 is the 6-byte version.
start [code]
stop [code]
eject [code]
ingest [code]
Start, stop, eject, and ingest are synonyms for Start/Stop Unit
with different default values of code. Start/Stop Unit is typi‐
cally used to spin up and spin down a rotating disk drive. Code
is 0 to stop, 1 to start and 3 to eject (if the device supports
ejection of the medium).
capacity
Read Capacity reports the number of blocks and the block size of
a disk.
The following commands are specific to CD and CD-R/RW devices. A brief
description of each is given; see the SCSI-3 Multimedia Commands (MMC)
Specification for details of arguments and interpretation of the re‐
sults.
blank [track/LBA[type]]
Erase a CD-RW disk. Type identifies the method and coverage of
the blanking.
rtoc [track/session-number[ses]]
The Read TOC/PMA command transfers data from one of the tables
of contents (TOC or PMA) on the CD medium.
rdiscinfo
(Note the spelling.) Provides information about disks, includ‐
ing incomplete CD-R/RW.
rtrackinfo [track]
Provides information about a track, regardless of its status.
cdpause
cdresume
Pause/resume playback.
cdstop Stop playback.
cdplay [track-number] or [-r[LBA[length]]]
Play audio. With no arguments, starts at the beginning of the
medium. If a track number is given, the table of contents is
read to find the playback start point. If the -r option is
given, block addressing is used to find the playback start
point.
cdload [slot]
cdunload [slot]
Load/unload a disk from a changer.
cdstatus
Read the mechanism status.
The following commands are specific to Media Changer devices. A brief
description of each is given; see the SCSI-3 Medium Changer Commands
(SMC) Specification for details of arguments.
einit Initialize element status.
estatus type [length]
Report the status of the internal elements. Type 0 reports all
element types.
mmove transport source destination[invert]
Move medium.
FILES
/dev/sdXX/raw
raw SCSI interface for command, I/O, and status.
SOURCE
/sys/src/cmd/scuzz
SEE ALSO
sd(3)
Small Computer System Interface - 2 (X3T9.2/86-109), Global Engineering
Documents
SCSI Bench Reference, ENDL Publications
SCSI-3 Multimedia Commands (MMC) Specification, www.t10.org
SCSI-3 Medium Changer Commands (SMC) Specification, www.t10.org
BUGS
Only a limited subset of SCSI commands has been implemented (as
needed).
Only one target can be open at a time.
LUNs other than 0 are not supported.
No way to force 10-byte commands, though they are the default.
Should be recoded to use scsi(2) in order to get more complete sense
code descriptions.
Scuzz betrays its origins by spelling rdiscinfo with a c even though
the devices it manipulates are spelled with a k.
The max-xfer value is currently limited to 245760 to limit kernel mem‐
ory consumption.
It may be necessary to set max-xfer to exactly the block size used to
write a tape in order to read it on some drives.
SCUZZ(8)