READCD(1) 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 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
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
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 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
similar name as with the f= option but the suffix .toc added.

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 applicable 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 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.
gnuplot. 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
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
The target device to the dev= option refers to
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 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= 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 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 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
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 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
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 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.

-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

-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
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 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
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.

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.

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 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/reconnect 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:

+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.
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
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 developer mailing list via this URL:

https://lists.sourceforge.net/lists/listinfo/cdrtools-developers

AUTHOR

Joerg Schilling
Seestr. 110
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.schilling@fokus.fraunhofer.de

To subscribe, use:

https://lists.sourceforge.net/lists/listinfo/cdrtools-developers
or https://lists.sourceforge.net/lists/listinfo/cdrtools-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)