Schily's USER COMMANDS READCD(1)
NAME
readcd - read or write data Compact Discs or related madia
SYNOPSIS
readcd [ dev=device ][ options ]
DESCRIPTION
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 tar-
get 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
/etc/default/cdrecord exists, the parameter to the dev=
option may also be a drive name label in said file (see
FILES section).
OPTIONS
If no options except the dev= option have been specified,
readcd goes into interactive mode. Select a primary func-
tion and then follow the instructions.
Informative options
-help
display version information for readcd on standard out-
put.
-version
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.
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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.
-c2scan
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.
-cxscan
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.
-edc-corr
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 applica-
ble with CD media and currently only supports plain
2048 Byte CD-ROM sectors.
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.
-factor
Output the speed values for meshpoints=# as factor
based on single speed of the current medium. This only
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works if readcd is able to determine the current medium
type.
-fulltoc
Retrieve a full TOC from the current disk and print it
in hex.
meshpoints=#
Print read-speed at # locations. The purpose of this
option is to create a list of read speed values suit-
able for e.g. gnuplot. The speed values are calcu-
lated assuming that 1000 bytes are one kilobyte as
documented in the SCSI standard. The output data
created for this purpose is written to stdout.
-nocorr
Switch the drive into a mode where it ignores read
errors in data sectors that are a result of uncorrect-
able ECC/EDC errors before reading. If readcd com-
pletes, the error recovery mode of the drive is
switched back to the remembered old mode.
-noerror
Do not abort if the high level error checking in readcd
found an uncorrectable error in the data stream.
-notrunc
Do not truncate the output file when opening it.
-overhead
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.
-pi8scan
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.
-pifscan
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.
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-plot
This option modified the behavior for -cxscan, -pi8scan
and -pifscan. The output is better suited for gnuplot.
retries=#
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 sec-
tors.
sectors=range
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.
speed=#
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 device.
SCSI options
dev=target
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
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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 dev-
ice is: dev= devicename:scsibus,target, 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,
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 sup-
ported transport layers for your platform, use dev=
HELP:
Portability Background
To make readcd portable to all UNIX platforms, the
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syntax dev= devicename:scsibus,target, 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/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 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 /etc/default/cdrecord exists, and if the
argument to the dev= option or the CDR_DEVICE environ-
ment does not contain the characters ',', '/', '@' or
':', it is interpreted as a device label name that was
defined in the file /etc/default/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 incre-
ment 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.
-scanbus
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 + tar-
get
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scgopts=list
A comma separated list of SCSI options that are handled
by libscg. 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 com-
mands.
spt=#
Set the maximum number of sectors per transfer.
timeout=#
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 operat-
ing 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 experi-
menting with the ts= option.
-V Increment the verbose level with respect of SCSI com-
mand 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.
EXAMPLES
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.
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To read the complete media from a CD-ROM writing the data to
the file cdimage.raw:
readcd dev=2,0 f=cdimage.raw
To read sectors from range 150 ... 10000 from a CD-ROM writ-
ing 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 filesys-
tem image from mkisofs) to a DVD-RAM, call:
readcd dev=2,0 -w f=cdimage.raw
ENVIRONMENT
RSH If the RSH environment is present, the remote connec-
tion 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 connection.
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 ini-
tiated rcmd(3) connection.
RSCSI
If the RSCSI environment is present, the remote SCSI
server will not be the program /opt/schily/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.
EXIT STATUS
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.
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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.
FILES
SEE ALSO
cdrecord(1), mkisofs(8), scg(7), fbk(7), rcmd(3), ssh(1).
NOTES
If you don't want to allow users to become root on your sys-
tem, 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 disks.
You should not connect old drives that do not support
disconnect/reconnect to either the SCSI bus that is con-
nected 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.
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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).
DIAGNOSTICS
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 command.
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 avail-
able, 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 replace-
able unit.
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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 valid.
The eight line reports the timeout set up for this command
and the time that the command really needed to complete.
BUGS
CREDITS
MAILING LISTS
If you want to actively take part on the development of
cdrecord, you may join the developer mailing list via this
URL:
https://lists.sourceforge.net/lists/listinfo/cdrtools-
developers
AUTHOR
Joerg Schilling
D-13353 Berlin
Germany
Additional information can be found on:
http://cdrecord.org/private/cdrecord.html
If you have support questions, send them to:
cdrtools-support@lists.sourceforge.net
If you have definitely found a bug, send a mail to:
cdrtools-developers@lists.sourceforge.net
or joerg@schily.net
To subscribe, use:
https://lists.sourceforge.net/lists/listinfo/cdrtools-
developers
or https://lists.sourceforge.net/lists/listinfo/cdrtools-
support
SOURCE DOWNLOAD
A frequently updated source code for the cdrtools is
included in the schilytools project and may be retrieved
from the schilytools project at Sourceforge at:
http://sourceforge.net/projects/schilytools/
The download directory is:
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http://sourceforge.net/projects/schilytools/files/
Check for the schily-*.tar.bz2 archives.
Less frequently updated source code for the cdrtools is at:
http://sourceforge.net/projects/cdrtools/files/
and
http://sourceforge.net/projects/cdrtools/files/alpha
Separate project informations for the cdrtools project may
be retrieved from:
http://cdrecord.org
INTERFACE STABILITY
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.
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