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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
       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
              similar name as with the f= option but the suffix .toc added.

              Note that reading in clone mode results in having no error
              correction 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

       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
              single 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.
              gnuplot.  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
              specified 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
              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:@ .

              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
              simulation of this driver.  Possible syntax is: dev=
              scsibus,target,lun or dev= target,lun.  In the latter case, the
              CD/DVD/BluRay-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= devicename:@,lun may be used
              instead of dev= devicename:scsibus,target,lun.

              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
              commands 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
              specific 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
              notation, 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
              reason 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
              computed 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
              timeout, 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
              better 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
              transfer size of 256 kB. If libscg gets lower values from the
              operating 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
              transport 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/reconnect 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
              cannot 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,
       followed 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
       current command, the text deferred error is appended.

       The sixth line is the error text for the sense code and the sense
       qualifier 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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