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

       readcd -	read or	write data Compact Discs or related madia

       readcd [	dev=device ][ options ]

       Readcd is used to read or write Compact Discs.

   Device naming
       Most  users do not need to care about device naming at all.  If no dev=
       option was specified, readcd implements auto  target  support  and  au-
       tomagically  finds the drive in case that exactly one CD-ROM type drive
       is available in the system.  In case that more  than  one  CD-ROM  type
       drive  exists  on the system, a list of possible	device name parameters
       may be retrieved	with readcd -scanbus or	from the target	 example  from
       the output of readcd dev=help, then the dev= parameter may be set based
       on the device listing.

       The device parameter to the dev=	option explained below refers  to  the
       SCSI CAM	standard notation for scsibus/target/lun of the	CD/DVD/BluRay-
       Recorder.  If a file /usr/local/etc/cdrecord exists, the	 parameter  to
       the  dev= option	may also be a drive name label in said file (see FILES

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

   Informative options
       -help  display version information for readcd on	standard output.

	      Print version information	and exit.

       -v     Increment	the level of general verbosity by one.	This  is  used
	      e.g. to display the progress of the process.

   Readcd functional options
       -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.

	      Note  that reading in clone mode results in having no error cor-
	      rection at sub-channel level. Even in  the  main	data  channel,
	      there  is	less error correction than with	other read modes. This
	      results in a slightly quality degradation. Avoid	copying	 audio
	      CDs in clone mode	for this reason.

	      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.

	      Scans  the  whole	CD or the range	specified by the sectors=range
	      for C1/C2/CU errors.  In non-verbose mode,  only	a  summary  is
	      printed.	 With  -v,  a  line  for each non error	free second is
	      printed.	with -vv, a line for each  second  is  printed.	  This
	      scan method only works for a few drives.

	      In  this mode, readcd reads CD data sectors in uncorrected audio
	      mode and then tries to correct the data using  the  ECC/EDC  de-
	      coder  library  from Heiko Eissfeldt. As this library implements
	      looping over two layers of error correction, readcd may be  able
	      to correct more data than	the firmware of	the CD-ROM drive.

	      This  option  is currently experimental and only applicable with
	      CD media and currently only supports plain 2048 Byte CD-ROM sec-

       f=file Specify  the  filename where the output should be	written	or the
	      input should be taken from. Using	'-'  as	 filename  will	 cause
	      readcd to	use stdout resp. stdin.

	      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.

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

	      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	output
	      data created for this purpose is written to stdout.

	      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.

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

	      Do not truncate the output file when opening it.

	      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.

	      Scans the	whole DVD or the range specified by the	 sectors=range
	      for  pisum8  errors.   In	 non-verbose  mode,  only a summary is
	      printed.	With -v, a line	for each non error free	block of  8  *
	      32  kB is	printed.  with -vv, a line for each block of 8 * 32 kB
	      is printed.  This	scan method only works for a few drives.

	      Scans the	whole DVD or the range specified by the	 sectors=range
	      for pif errors.  In non-verbose mode, only a summary is printed.
	      With -v, a line for each non  error  free	 block	of  32	kB  is
	      printed.	 with  -vv, a line for each block of 32	kB is printed.
	      This scan	method only works for a	few drives.

       -plot  This option modified the	behavior  for  -cxscan,	 -pi8scan  and
	      -pifscan.	 The output is better suited for gnuplot.

	      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.

	      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.

       -w     Switch to	write mode.  Writing is	only possible to  DVD-RAM  me-
	      dia.  For	other media, use cdrecord instead.  Note that cdrecord
	      also supports to write DVD-RAM media.

	      If this option is	not present, readcd reads from	the  specified

   SCSI	options
	      Set  the	SCSI  target for the CD/DVD/BluRay-Recorder, see notes
	      above.  A	typical	target device specification is dev=1,6,0 .  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 spe-
	      cific manuals of the target operating system.  On	a FreeBSD sys-
	      tem  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:@ .

	    General SCSI addressing
	      The  target  device  to  the  dev= option	refers to the SCSI CAM
	      standard notation	for scsibus/target/lun of  the	CD/DVD/BluRay-
	      Recorder.	 Communication	on SunOS is done with the SCSI general
	      driver scg.  Other operating systems are using a library simula-
	      tion  of	this  driver.	Possible  syntax is: dev= scsibus,tar-
	      get,lun or dev= target,lun.  In the latter case, the CD/DVD/Blu-
	      Ray-Recorder  has	to be connected	to the default SCSI bus	of the
	      machine.	Scsibus, target	and lun	are integer numbers.  Some op-
	      erating 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 de-
	      vice, a shorthand	in the form dev= devicename:@ or dev=  device-
	      name:@,lun  may  be used instead of dev= devicename:scsibus,tar-

	    Remote SCSI	addressing
	      To access	remote SCSI devices, you need to prepend the SCSI  de-
	      vice  name by a remote device indicator. The remote device indi-
	      cator 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.  In order to
	      allow remote access to a specific	 host,	the  rscsi(1)  program
	      needs to be present and configured on the	host.

	    Alternate SCSI transports
	      Cdrecord	is  completely	based  on SCSI commands	but this is no
	      problem as all CD/DVD/BluRay writers ever	made use SCSI commands
	      for  the	communication.	Even ATAPI drives are just SCSI	drives
	      that inherently use the ATA packet  interface  as	 SCSI  command
	      transport	 layer	build  into  the IDE (ATA) transport.  You may
	      need to specify an alternate  transport  layer  on  the  command
	      line  if	your  OS  does not implement a fully integrated	kernel
	      driver subsystem that allows to access any drive using SCSI com-
	      mands via	a single unique	user interface.

	      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= HELP:

	    Portability	Background
	      To  make	readcd portable	to all UNIX platforms, the syntax dev=
	      devicename:scsibus,target,lun is preferred as it hides  OS  spe-
	      cific knowledge about device names from the user.	 A specific OS
	      may not necessarily support a way	to specify a real device  file
	      name nor a way to	specify	scsibus,target,lun.

	      Scsibus 0	is the default SCSI bus	on the machine.	Watch the boot
	      messages for more	information or look  into  /var/run/dmesg.boot
	      for  more	 information  about the	SCSI configuration of your ma-
	      chine.  If you have problems to figure out what values for scsi-
	      bus,target,lun should be used, try the -scanbus option of	readcd
	      described	below.

	    Using logical names	for devices
	      If no dev	option is present, readcd will try to get  the	device
	      from the CDR_DEVICE environment.

	      If a file	/usr/local/etc/cdrecord	exists,	and if the argument to
	      the dev= option or the CDR_DEVICE	environment does  not  contain
	      the  characters ',', '/',	'@' or ':', it is interpreted as a de-
	      vice  label  name	 that  was  defined  in	 the   file   /usr/lo-
	      cal/etc/cdrecord (see FILES section).

	    Autotarget Mode
	      If  no  dev= option and no CDR_DEVICE environment	is present, or
	      if it only contains a transport specifyer	but no	address	 nota-
	      tion,  readcd  tries  to	scan the SCSI address space for	CD-ROM
	      drives.  If exactly one is found,	this is	used by	default.

       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.

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

	      A	 comma separated list of SCSI options that are handled by lib-
	      scg.  The	implemented options may	be uptated indepentendly  from
	      applications.   Currently, one option: ignore-resid is supported
	      to work around a Linux kernel bug.

       -silent,	-s
	      Do not print out a status	report for failed SCSI commands.

	      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.

       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 maximum  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 ex-
	      perimenting with the ts= option.

       -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  er-
	      ror  messages you	should use this	flag to	get more detailed out-
	      put.  -VV	will show data buffer content in addition.   Using  -V
	      or -VV slows down	the process.

       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.

       The following exit codes	are used:

       0      No error appeared.

       -1     A	specific error appeared. This may be a usage error  caused  by
	      an illegal command line or another error with a problem specific
	      error message from readcd.

       -2     An unspecified error appeared during the process of  talking  to
	      the  drive.   See	 SCSI error message for	more informations. The
	      section DIAGNOSTICS below	contains an explanation	on how to read
	      SCSI error messages.

       Note  that older	operating systems and older shells may not support the
       full 32 bit range of the	exit code and mask the value with  0xFF.  This
       results	in shortened exit codes	in the range 0..255 where -1 is	mapped
       to 255.

       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?   de-
       vices  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 Linux	SCSI generic driver.  You should  note
       that  readcd  uses  a layer, that tries to emulate the functionality of
       the scg driver on top of	the drives of the local	operating system.  Un-
       fortunately, the	sg driver on Linux has several flaws:

       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 er-
       ror 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 developer mailing list via this URL:

       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:

       The interfaces provided by readcd are designed for long term stability.
       As  readcd  depends  on interfaces provided by the underlying operating
       system, the stability of	the interfaces offered by  readcd  depends  on
       the  interface  stability of the	OS interfaces.	Modified interfaces in
       the OS may enforce modified interfaces in readcd.

Joerg Schilling		    Version 3.02 2017/06/06		     READCD(1)


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