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READCD(1)		    Schily's USER COMMANDS		     READCD(1)

       readcd -	read or	write data Compact Discs

       readcd dev=device [ options ]

       Readcd is used to read or write Compact Discs.

       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  access  SCSI	 devices  via  alternate transport layers, you need to
       prepend the SCSI	device name  by	 a  transport  layer  indicator.   The
       transport  layer	 indicator may be something like USCSI:	or ATAPI:.  To
       get a list of supported transport layers	for your  platform,  use  dev=

       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/run/dmesg.boot  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.

       If  no  options except the dev= option have been	specified, readcd goes
       into interactive	mode.  Select a	primary	function and then  follow  the

	      Print version information	and exit.

	      Sets  the	SCSI target for	the drive, see notes above.  A typical
	      device specification is dev=6,0 .	 If a filename	must  be  pro-
	      vided  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  sup-
	      port,  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 /usr/local/etc/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.

       debug=#,	-d
	      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.

       kdebug=#, kd=#
	      Tell the scg-driver to modify the	kernel debug value while  SCSI
	      commands are running.

       -silent,	-s
	      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  filename where the output should be	written	or the
	      inout should be taken from. Using	'-'  as	 filename  will	 cause
	      readcd to	use stdout resp. stdin.

       -w     Switch  to  write	 mode.	If  this option	is not present,	readcd
	      reads from the specified device.

	      Scans the	whole CD or the	range specified	by  the	 sectors=range
	      for C2 errors. C2	errors are errors that are uncorrectable after
	      the second stage of the 24/28 + 28/32  Reed  Solomon  correction
	      system  at  audio	level (2352 bytes sector size).	If an audio CD
	      has C2 errors, interpolation is needed to	hide the errors. If  a
	      data  CD has C2 errors, these errors are in most cases corrected
	      by the ECC/EDC code that makes  2352  bytes  out	of  2048  data
	      bytes.  The  ECC/EDC code	should be able to correct about	100 C2
	      error bytes per sector.

	      If you find C2 errors you	may want to reduce the speed using the
	      speed=  option as	C2 errors may be a result of dynamic unbalance
	      on the medium.

	      Scan all SCSI devices on all SCSI	busses and print  the  inquiry
	      strings.	This  option  may  be used to find SCSI	address	of the
	      devices on a system.  The	numbers	printed	out as labels are com-
	      puted by:	bus * 100 + target

	      Specify a	sector range that should be read.  The range is	speci-
	      fied by the starting sector number, a minus sign and the	ending
	      sector  number.	The end	sector is not included in the list, so
	      sectors=0-0 will not read	anything and may be used to check  for
	      a	CD in the drive.

	      Set the speed factor of the read or write	process	to #.  # is an
	      integer, representing a multiple of the audio  speed.   This  is
	      about  150  KB/s for CD-ROM and about 172	KB/s for CD-Audio.  If
	      no speed option is present, readcd will use maximum speed.  Only
	      MMC  compliant  drives will benefit from this option.  The speed
	      of non MMC drives	is not changed.

	      Using a lower speed may increase the readability of a CD or DVD.

       ts=#   Set  the	maximum	 transfer size for a single SCSI command to #.
	      The syntax for the ts= option is the same	as for	cdrecord  fs=#
	      or sdd bs=#.

	      If no ts=	option has been	specified, readcd defaults to a	trans-
	      fer size of 256 kB. If libscg gets lower values from the operat-
	      ing  system,  the	 value	is reduced to the maimum value that is
	      possible with the	current	operating system.  Sometimes,  it  may
	      help  to	further	reduce the transfer size or to enhance it, but
	      note that	it may take a long time	to  find  a  better  value  by
	      experimenting with the ts= option.

	      Do not truncate the output file when opening it.

	      Retrieve a full TOC from the current disk	and print it in	hex.

       -clone Do  a  clone  read.  Read	the CD with all	sub-channel data and a
	      full TOC.	 The full TOC data will	be put into a file with	 simi-
	      lar name as with the f= option but the suffix .toc added.

	      Do not abort if the high level error checking in readcd found an
	      uncorrectable error in the data stream.

	      Switch the drive into a mode where it  ignores  read  errors  in
	      data  sectors  that are a	result of uncorrectable	ECC/EDC	errors
	      before reading.  If readcd completes, the	error recovery mode of
	      the drive	is switched back to the	remembered old mode.

	      Set  the retry count for high level retries in readcd to #.  The
	      default is to do 128 retries which may be	too much if  you  like
	      to read a	CD with	many unreadable	sectors.

	      Meter the	SCSI command overhead time.  This is done by executing
	      several commands 1000 times and printing the total time used. If
	      you  divide  the	displayed  times  by 1000, you get the average
	      overhead time for	a single command.

	      Print read-speed at # locations.	The purpose of this option  is
	      to  create  a  list of read speed	values suitable	for e.g.  gnu-
	      plot.  The speed values are calculated assuming that 1000	 bytes
	      are  one kilobyte	as documented in the SCSI standard.  The ouput
	      data created for this purpose is written to stdout.

	      Output the speed values for meshpoints=# as factor based on sin-
	      gle  speed  of the current medium.  This only works if readcd is
	      able to determine	the current medium type.

       For all examples	below, it will be assumed that the drive is  connected
       to the primary SCSI bus of the machine. The SCSI	target id is set to 2.

       To read the complete media from a CD-ROM	writing	the data to  the  file

	   readcd dev=2,0 f=cdimage.raw

       To read sectors from range 150 ... 10000	from a CD-ROM writing the data
       to the file cdimage.raw:

	   readcd dev=2,0 sectors=150-10000 f=cdimage.raw

       To write	the data from the file cdimage.raw (e.g.  a  filesystem	 image
       from mkisofs) to	a DVD-RAM, call:

	   readcd dev=2,0 -w f=cdimage.raw

       RSH    If  the  RSH  environment	is present, the	remote connection will
	      not be created via rcmd(3) but by	calling	the program pointed to
	      by  RSH.	 Use  e.g.   RSH=/usr/bin/ssh to create	a secure shell

	      Note that	this forces cdrecord to	create a pipe  to  the	rsh(1)
	      program  and  disallows  cdrecord	to directly access the network
	      socket to	the remote server.  This makes it impossible to	set up
	      performance parameters and slows down the	connection compared to
	      a	root initiated rcmd(3) connection.

       RSCSI  If the RSCSI environment is present, the remote SCSI server will
	      not be the program /usr/local/sbin/rscsi but the program pointed
	      to by RSCSI.  Note that the remote SCSI server program name will
	      be  ignored if you log in	using an account that has been created
	      with a remote SCSI server	program	as login shell.

       cdrecord(1), mkisofs(8),	rcmd(3), ssh(1).

       If you don't want to allow users	to become root on your system,	readcd
       may  safely be installed	suid root. This	allows all users or a group of
       users with no root privileges to	use readcd.  Readcd in this case  will
       only allow access to CD-ROM type	drives-	To give	all user access	to use
       readcd, enter:

	    chown root /usr/local/bin/readcd
	    chmod 4711 /usr/local/bin/readcd

       To give a restricted group of users access to readcd enter:

	    chown root /usr/local/bin/readcd
	    chgrp cdburners /usr/local/bin/readcd
	    chmod 4710 /usr/local/bin/readcd

       and add a group cdburners on your system.

       Never give write	permissions  for  non  root  users  to	the  /dev/scg?
       devices	unless	you  would allow anybody to read/write/format all your

       You should not connect old drives that do not support disconnect/recon-
       nect to either the SCSI bus that	is connected to	the CD-Recorder	or the
       source disk.

       When using readcd with the  broken  Linux  SCSI	generic	 driver.   You
       should  note  that  readcd uses a hack, that tries to emulate the func-
       tionality of the	scg driver.  Unfortunately, the	sg driver on Linux has
       several severe bugs:

       o      It cannot	see if a SCSI command could not	be sent	at all.

       o      It cannot	get the	SCSI status byte.  Readcd for that reason can-
	      not report failing SCSI commands in some situations.

       o      It cannot	get real DMA count of transfer.	  Readcd  cannot  tell
	      you if there is an DMA residual count.

       o      It  cannot get number of bytes valid in auto sense data.	Readcd
	      cannot tell you if device	transfers no sense data	at all.

       o      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 command.

       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	really needed to complete.

       If  you	want to	actively take part on the development of cdrecord, you
       may join	the cdwriting mailing list by sending mail to:

       and include the word subscribe in the body.  The	mail  address  of  the
       list is:

       Joerg Schilling
       Seestr. 110
       D-13353 Berlin

       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			     READCD(1)


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