readcd(1)
READCD(1) Schily's USER COMMANDS READCD(1)
NAME
readcd - read or write data Compact Discs
SYNOPSIS
readcd dev=device [ options ]
DESCRIPTION
Readcd is used to read or write Compact Discs.
The device refers to scsibus/target/lun of the drive. Com-
munication 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 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, 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,
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= HELP:
To make readcd portable to all UNIX platforms, the syntax
dev= devicename:scsibus,target, 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,target,lun.
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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 confi-
guration 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.
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.
-version
Print version information and exit.
dev=target
Sets the SCSI target for the drive, see notes above. A
typical device specification is dev=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 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 different 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
characters ',', '/', '@' or ':', it is interpreted as
an label name that may be found in the file
/etc/default/cdrecord (see FILES section).
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
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used.
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.
-silent, -s
Do not print out a status report for failed SCSI com-
mands.
-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 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.
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.
-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
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dynamic unbalance on the medium.
-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
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.
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
maimum 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.
-notrunc
Do not truncate the output file when opening it.
-fulltoc
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
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file with similar name as with the f= option but the
suffix .toc added.
-noerror
Do not abort if the high level error checking in readcd
found an uncorrectable error in the data stream.
-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.
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.
-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.
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 ouput data
created for this purpose is written to stdout.
-factor
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.
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.
To read the complete media from a CD-ROM writing the data to
the file cdimage.raw:
readcd dev=2,0 f=cdimage.raw
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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.
FILES
SEE ALSO
cdrecord(1), mkisofs(1), 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
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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 broken Linux SCSI generic driver.
You should note that readcd uses a hack, that tries to emu-
late the functionality 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 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).
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.
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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.
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 cdwriting mailing list by sending
mail to:
other-cdwrite-request@lists.debian.org
and include the word subscribe in the body. The mail
address of the list is:
cdwrite@lists.debian.org
AUTHOR
Joerg Schilling
Seestr. 110
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D-13353 Berlin
Germany
Additional information can be found on:
http://www.fokus.fhg.de/usr/schilling/cdrecord.html
If you have support questions, send them to:
cdrecord-support@berlios.de
or other-cdwrite@lists.debian.org
If you have definitely found a bug, send a mail to:
cdrecord-developers@berlios.de
or schilling@fokus.fhg.de
To subscribe, use:
http://lists.berlios.de/mailman/listinfo/cdrecord-developers
or http://lists.berlios.de/mailman/listinfo/cdrecord-support
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