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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. Communication on
SunOS is done with the SCSI general driver scg. Other operating sys-
tems 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,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= devi-
cename:@ or dev= devicename:@,lun may be used instead of dev= device-
name:scsibus,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 transport layers for your platform, use dev=
HELP:
To make readcd portable to all UNIX platforms, the syntax dev= device-
name: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
scsibus,target,lun.
Scsibus 0 is the default SCSI bus on the machine. Watch the boot mes-
sages 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 cdrecord.
OPTIONS
If no options except the dev= option have been specified, readcd goes
into interactive mode. Select a primary function 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 pro-
vided 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 charac-
ters ',', '/', '@' or ':', it is interpreted as an label name
that may be found in the file /etc/cdrecord.conf (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 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
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.
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 open-
ing a driver for libscg. as well as with sector sizes and sec-
tor 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 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.
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 cor-
rection 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.
-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 + target
sectors=range
Specify a sector range that should be read. The range is spec-
ified by the starting sector number, a minus sign and the end-
ing 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 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.
-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 file with simi-
lar 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 uncorrectable 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 execut-
ing 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 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 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
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 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
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 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 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 discon-
nect/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 func-
tionality of the scg driver. Unfortunately, the sg driver on Linux
has several severe bugs:
? It cannot see if a SCSI command could not be sent at all.
? It cannot get the SCSI status byte. Readcd for that reason
cannot report failing SCSI commands in some situations.
? It cannot get real DMA count of transfer. Readcd cannot tell
you if there is an DMA residual count.
? It cannot get number of bytes valid in auto sense data. Readcd
cannot tell you if device transfers no sense data at all.
? 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 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 cur-
rent 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 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
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
Joerg Schilling Version 2.0 READCD(1)
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