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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 simula-
tion of this driver. Possible syntax is: dev= scsi-
bus,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= device-
name: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 short-
hand in the form dev= devicename:@ or dev= device-
name:@,lun may be used instead of dev= devicename:scsi-
bus,target,lun.
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 trans-
port layers for your platform, use dev= HELP:
To make readcd portable to all UNIX platforms, the syntax
dev= devicename:scsibus,target,lun 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 scsi-
bus,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 con-
figuration of your machine. If you have problems to fig-
ure 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 manu-
als 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:@ .
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 inter-
preted 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 com-
mand runs correctly with a raised command timeout,
please report the better timeout value and the cor-
responding command to the author of the program.
If no timeout option is present, a default timeout
of 40 seconds is used.
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.
-silent, -s
Do not print out a status report for failed SCSI
commands.
-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
command transport by one. This helps to debug
problems during the process, that occur in the CD-
Recorder. If you get incomprehensible error mes-
sages you should use this flag to get more detailed
output. -VV will show data buffer content in addi-
tion. 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 pre-
sent, 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 dynamic unbalance on the medium.
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.
-notrunc
Do not truncate the outputfile 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 but
into a 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 uncor-
rectable ECC/EDC errors before reading. If readcd
completes, 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 sectors.
-overhead
Meter the SCSI command overhead time. This is done
by executing several commands 1000 times and print-
ing the total time used. If you divide the dis-
played times by 1000, you get the average overhead
time for a single command.
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
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
ENVIRONMENT
RSH If the RSH environment is present, the remote con-
nection 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 connec-
tion.
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 perfor-
mance parameters and slows down the connection com-
pared to a root initiated 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
system, readcd may safely be installed suid root. This
allows all users or a group of users with no root privi-
leges 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 dis-
connect/reconnect to either the SCSI bus that is connected
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 emulate 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 ker-
nel. It usually is: I/O error unless other problems hap-
pen. 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 pos-
sible 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
available, followed by the segment number that is only
valid if the command was a copy command. If the error mes-
sage 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 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 send-
ing 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
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
Of 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-develop-
ers
or http://lists.berlios.de/mailman/listinfo/cdrecord-sup-
port
Joerg Schilling Version 2.0 READCD(1)
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