SCGCHECK(1) Schily´s USER COMMANDS SCGCHECK(1)NAMEscgcheck - check and validate the ABI of libscg
SYNOPSISscgcheck [ options ]
Scgcheck is used to check and verify the Application Binary Interface
The device refers to scsibus/target/lun of the drive. Communication on
SunOS is done with the SCSI general driver scg. Other operating sys‐
tems are using a library simulation of this driver. Possible syntax
is: dev= scsibus,target,lun or dev= target,lun. In the latter case,
the drive has to be connected to the default SCSI bus of the machine.
Scsibus, target and lun are integer numbers. Some operating systems or
SCSI transport implementations may require to specify a filename in
addition. In this case the correct syntax for the device is: dev=
devicename:scsibus,target,lun or dev= devicename:target,lun. If the
name of the device node that has been specified on such a system refers
to exactly one SCSI device, a shorthand in the form dev= devicename:@
or dev= devicename:@,lun may be used instead of dev= devicename:scsi‐
To access remote SCSI devices, you need to prepend the SCSI device name
by a remote device indicator. The remote device indicator is either
REMOTE:user@host: or REMOTE:host:
A valid remote SCSI device name may be: REMOTE:user@host: to allow
remote SCSI bus scanning or REMOTE:user@host:1,0,0 to access the SCSI
device at host connected to SCSI bus # 1,target 0 lun 0.
To make readcd portable to all UNIX platforms, the syntax dev= device‐
name:scsibus,target,lun is preferred as is hides OS specific knowledge
about device names from the user. A specific OS must not necessarily
support a way to specify a real device file name nor a way to specify
Scsibus 0 is the default SCSI bus on the machine. Watch the boot mes‐
sages for more information or look into /var/adm/messages for more
information about the SCSI configuration of your machine. If you have
problems to figure out what values for scsibus,target,lun should be
used, try the -scanbus option of cdrecord.
Print version information and exit.
Sets the SCSI target default for SCSI Bus scanning test, see
notes above. This allows e.g. to specify to use Solaris USCSI
or remote SCSI for the bus scanning case.
For the non bus scanning case, a typical device specification is
dev=6,0 . If a filename must be provided together with the
numerical target specification, the filename is implementation
specific. The correct filename in this case can be found in the
system specific manuals of the target operating system. On a
FreeBSD system without CAM support, you need to use the control
device (e.g. /dev/rcd0.ctl). A correct device specification in
this case may be dev=/dev/rcd0.ctl:@ .
On Linux, drives connected to a parallel port adapter are mapped
to a virtual SCSI bus. Different adapters are mapped to differ‐
ent targets on this virtual SCSI bus.
If no dev option is present, cdrecord will try to get the device
from the CDR_DEVICE environment.
If the argument to the dev= option does not contain the charac‐
ters ',', '/', '@' or ':', it is interpreted as an label name
that may be found in the file /etc/default/cdrecord (see FILES
Set the default SCSI command timeout value to # seconds. The
default SCSI command timeout is the minimum timeout used for
sending SCSI commands. If a SCSI command fails due to a time‐
out, you may try to raise the default SCSI command timeout above
the timeout value of the failed command. If the command runs
correctly with a raised command timeout, please report the bet‐
ter timeout value and the corresponding command to the author of
the program. If no timeout option is present, a default timeout
of 40 seconds is used.
Set the misc debug value to # (with debug=#) or increment the
misc debug level by one (with -d). If you specify -dd, this
equals to debug=2. This may help to find problems while opening
a driver for libscg. as well as with sector sizes and sector
types. Using -debug slows down the process and may be the rea‐
son for a buffer underrun.
Tell the scg-driver to modify the kernel debug value while SCSI
commands are running.
Do not print out a status report for failed SCSI commands.
-v Increment the level of general verbosity by one. This is used
e.g. to display the progress of the process.
-V Increment the verbose level with respect of SCSI command trans‐
port by one. This helps to debug problems during the process,
that occur in the CD-Recorder. If you get incomprehensible
error messages you should use this flag to get more detailed
output. -VV will show data buffer content in addition. Using
-V or -VV slows down the process.
f=file Specify the log file to be used instead of check.log.
EXAMPLESFILESSEE ALSOcdrecord(1), readcd(1), mkisofs(1), scg(7).
When using scgckeck with the broken Linux SCSI generic driver. You
should note that scgcheck uses a hack, that tries to emulate the func‐
tionality of the scg driver. Unfortunately, the sg driver on Linux has
several severe bugs:
· It cannot see if a SCSI command could not be sent at all.
· It cannot get the SCSI status byte. Scgcheck for that reason
cannot report failing SCSI commands in some situations.
· It cannot get real DMA count of transfer. Scgcheck cannot tell
you if there is an DMA residual count.
· It cannot get number of bytes valid in auto sense data.
Scgcheck cannot tell you if device transfers no sense data at
· It fetches to few data in auto request sense (CCS/SCSI-2/SCSI-3
needs >= 18).
A typical error message for a SCSI command looks like:
readcd: I/O error. test unit ready: scsi sendcmd: no error
CDB: 00 20 00 00 00 00
status: 0x2 (CHECK CONDITION)
Sense Bytes: 70 00 05 00 00 00 00 0A 00 00 00 00 25 00 00 00 00 00
Sense Key: 0x5 Illegal Request, Segment 0
Sense Code: 0x25 Qual 0x00 (logical unit not supported) Fru 0x0
Sense flags: Blk 0 (not valid)
cmd finished after 0.002s timeout 40s
The first line gives information about the transport of the command.
The text after the first colon gives the error text for the system call
from the view of the kernel. It usually is: I/O error unless other
problems happen. The next words contain a short description for the
SCSI command that fails. The rest of the line tells you if there were
any problems for the transport of the command over the SCSI bus. fatal
error means that it was not possible to transport the command (i.e. no
device present at the requested SCSI address).
The second line prints the SCSI command descriptor block for the failed
The third line gives information on the SCSI status code returned by
the command, if the transport of the command succeeds. This is error
information from the SCSI device.
The fourth line is a hex dump of the auto request sense information for
The fifth line is the error text for the sense key if available, fol‐
lowed by the segment number that is only valid if the command was a
copy command. If the error message is not directly related to the cur‐
rent command, the text deferred error is appended.
The sixth line is the error text for the sense code and the sense qual‐
ifier if available. If the type of the device is known, the sense data
is decoded from tables in scsierrs.c . The text is followed by the
error value for a field replaceable unit.
The seventh line prints the block number that is related to the failed
command and text for several error flags. The block number may not be
The eight line reports the timeout set up for this command and the time
that the command realy needed to complete.
Additional information can be found on:
If you have support questions, send them to:
If you have definitely found a bug, send a mail to:
To subscribe, use:
Joerg Schilling Version 2.0 SCGCHECK(1)