READCD(1) Schily´s USER COMMANDS READCD(1)NAMEreadcd - read or write data Compact Discs or related madia
SYNOPSISreadcd [ 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 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 parame‐
ters 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 scsi‐
bus/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 function and then follow the
instructions.
Informative options
-help display version information for readcd on standard output.
-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 simi‐
lar name as with the f= option but the suffix .toc added.
Note that reading in clone mode results in having no error cor‐
rection 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 applicable with
CD media and currently only supports plain 2048 Byte CD-ROM sec‐
tors.
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 sin‐
gle speed of the current medium. This only 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 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 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 uncorrectable ECC/EDC errors
before reading. If readcd completes, 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.
-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 sectors.
sectors=range
Specify a sector range that should be read. The range is speci‐
fied 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 spe‐
cific manuals of the target operating system. On a FreeBSD sys‐
tem 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 scsibus/tar‐
get/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= 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 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 com‐
mands 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 spe‐
cific 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,tar‐
get,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 environment 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 nota‐
tion, 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 rea‐
son 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 com‐
puted by: bus * 100 + target
-silent, -s
Do not print out a status report for failed SCSI commands.
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 bet‐
ter 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 trans‐
fer size of 256 kB. If libscg gets lower values from the operat‐
ing 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 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.
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 compared 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.
FILESSEE ALSOcdrecord(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 disconnect/recon‐
nect 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:
· It cannot see if a SCSI command could not be sent at all.
· It cannot get the SCSI status byte. Readcd for that reason can‐
not 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, fol‐
lowed 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 qual‐
ifier 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.
BUGSCREDITSMAILING LISTS
If you want to actively take part on the development of cdrecord, you
may join the developer mailing list via this URL:
http://lists.berlios.de/mailman/listinfo/cdrecord-developers
AUTHOR
Joerg Schilling
Seestr. 110
D-13353 Berlin
Germany
Additional information can be found on:
http://cdrecord.berlios.de/private/cdrecord.html
If you have support questions, send them to:
cdrecord-support@berlios.de
If you have definitely found a bug, send a mail to:
cdrecord-developers@berlios.de
or joerg.schilling@fokus.fraunhofer.de
To subscribe, use:
http://lists.berlios.de/mailman/listinfo/cdrecord-developers
or http://lists.berlios.de/mailman/listinfo/cdrecord-support
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.
Joerg Schilling Version 3.0 READCD(1)
