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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
       automagically  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 parame-
       ters 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
	      decoder 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
	      media.  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
	      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= devi-
	      cename:@,lun may be used instead of dev= devicename:scsibus,tar-

	    Remote SCSI	addressing
	      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.
	      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
	      machine.	 If  you  have	problems to figure out what values for
	      scsibus,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
	      device	label	 name	that   was   defined   in   the	  file
	      /usr/local/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
	      devices on a system.  The	numbers	printed	out as labels are com-
	      puted by:	bus * 100 + target

       -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
	      experimenting 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
	      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.

       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 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.
       Unfortunately, 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
       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 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 2015/11/03		     READCD(1)


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