cdrtools/readcd/readcd.1

.\" @(#)readcd.1	1.50 17/06/06 Copyright 1996-2017 J. Schilling
.\"
.\" The contents of this file are subject to the terms of the
.\" Common Development and Distribution License, Version 1.0 only
.\" (the "License").  You may not use this file except in compliance
.\" with the License.
.\"
.\" See the file CDDL.Schily.txt in this distribution for details.
.\" A copy of the CDDL is also available via the Internet at
.\" http://www.opensource.org/licenses/cddl1.txt
.\"
.\" When distributing Covered Code, include this CDDL HEADER in each
.\" file and include the License file CDDL.Schily.txt from this distribution.
.\"
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.TH READCD 1 "Version 3.02 2017/06/06" "J\*org Schilling" "Schily\'s USER COMMANDS"
.SH NAME
readcd \- read or write data Compact Discs or related madia
.SH SYNOPSIS
.B readcd
[
.BI dev= device
][
.I options
]

.SH DESCRIPTION
.B Readcd
is used to read or write Compact Discs.
.PP
.SS "Device naming"
Most users do not need to care about device naming at all.
If no
.B dev=
option was specified, 
.B readcd
implements 
.B 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
.B "readcd \-scanbus
or from the target example from the output of
.BR "readcd dev=help" ,
then the
.B dev=
parameter may be set based on the device listing.
.PP
The
.I device
parameter to the
.B dev=
option
explained below refers to the
.B SCSI\ CAM
standard notation for
.IR scsibus / target / lun
of the CD/DVD/BluRay-Recorder.
If a file /etc/default/cdrecord exists, the parameter to the
.B dev=
option may also be a drive name label in said file (see FILES section).

.SH OPTIONS
.PP
If no options except the 
.I dev=
option have been specified, 
.B readcd
goes into interactive mode.
Select a primary function and then follow the instructions.
.PP
.SS "Informative options"
.TP
.B \-help
display version information for
.B readcd
on standard output.
.TP
.B \-version
Print version information and exit.
.TP
.B \-v
Increment the level of general verbosity by one.
This is used e.g. to display the progress of the process.
.SS "Readcd functional options"
.TP
.B \-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
.B f=
option but the suffix 
.B .toc
added.
.sp
Note that reading in
.B 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 
.B clone
mode for this reason.
.TP
.B \-c2scan
Scans the whole CD or the range specified by the 
.BI 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.
.sp
If you find C2 errors you may want to reduce the speed using the
.B speed=
option as C2 errors may be a result of dynamic unbalance on the medium.
.TP
.B \-cxscan
Scans the whole CD or the range specified by the 
.BI sectors= range
for C1/C2/CU errors.
In non-verbose mode, only a summary is printed.
With
.BR \-v ,
a line for each non error free second is printed.
with
.BR \-vv ,
a line for each second is printed.
This scan method only works for a few drives.
.TP
.B \-edc\-corr
In this mode,
.B readcd
reads CD data sectors in uncorrected audio mode 
and then tries to correct the data using the ECC/EDC decoder library
.\" Das Bl<42>de nroff kan nicht mit <20> umgehen (speziell ISO-8859-1 vs. UTF-8)
from Heiko Eissfeldt. As this library implements looping over two layers
of error correction, 
.B readcd
may be able to correct more data than the firmware of the CD-ROM drive.
.sp
This option is currently experimental and only applicable with 
CD media and currently only supports
plain 2048 Byte CD-ROM sectors.
.TP
.BI f= file
Specify the filename where the output should be written or the input should
be taken from. Using '\-' as filename will cause
.B readcd
to use 
.BR stdout " resp. " stdin .
.TP
.B \-factor
Output the speed values for
.BR meshpoints= #
as factor based on 
.I "single speed
of the current medium.
This only works if
.B readcd
is able to determine the current medium type.
.TP
.B \-fulltoc
Retrieve a full TOC from the current disk and print it in hex.
.TP
.BR meshpoints= #
Print read-speed at # locations.
The purpose of this option is to create a list of read speed values suitable
for e.g.
.BR 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 
.IR stdout .
.TP
.B \-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
.B readcd
completes, the error recovery mode of the drive is switched back to the remembered 
old mode.
.TP
.B \-noerror
Do not abort if the high level error checking in
.B readcd
found an uncorrectable error in the data stream.
.TP
.B \-notrunc
Do not truncate the output file when opening it.
.TP
.B \-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.
.TP
.B \-pi8scan
Scans the whole DVD or the range specified by the 
.BI sectors= range
for 
.B pisum8
errors.
In non-verbose mode, only a summary is printed.
With
.BR \-v ,
a line for each non error free block of 8 * 32 kB is printed.
with
.BR \-vv ,
a line for each block of 8 * 32 kB is printed.
This scan method only works for a few drives.
.TP
.B \-pifscan
Scans the whole DVD or the range specified by the 
.BI sectors= range
for 
.B pif
errors.
In non-verbose mode, only a summary is printed.
With
.BR \-v ,
a line for each non error free block of 32 kB is printed.
with
.BR \-vv ,
a line for each block of 32 kB is printed.
This scan method only works for a few drives.
.TP
.B \-plot
This option modified the behavior for
.BR \-cxscan ,
.BR \-pi8scan 
and
.BR \-pifscan .
The output is better suited for gnuplot.
.TP
.BI retries= #
Set the retry count for high level retries in
.B readcd
to 
.IR # .
The default is to do 128 retries which may be too much if you like to read a CD
with many unreadable sectors.
.TP
.BI 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 
.BR sectors= 0-0
will not read anything and may be used to check for a CD in the drive.
.TP
.BR 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 
.I speed
option is present, 
.B readcd
will use maximum speed.
Only MMC compliant drives will benefit from this option.
The speed of non MMC drives is not changed.
.sp
Using a lower speed may increase the readability of a CD or DVD.
.TP
.B \-w
Switch to write mode.
Writing is only possible to DVD-RAM media. For other media, use
.B cdrecord
instead.
Note that 
.B cdrecord
also supports to write DVD-RAM media.
.sp
If this option is not present,
.B readcd
reads from the specified device.
.SS "SCSI options"
.TP
.BI dev= target
Set the SCSI target for the CD/DVD/BluRay-Recorder, see notes above.
A typical target device specification is
.BI 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 
.I FreeBSD
system without 
.I CAM
support, you need to use the control device (e.g.
.IR /dev/rcd0.ctl ).
A correct device specification in this case may be
.BI dev= /dev/rcd0.ctl:@
\&.
.sp
.B \h'-2m'General SCSI addressing
.br
The
.I target device
to the 
.B dev=
option
refers to the
.B SCSI\ CAM
standard notation for
.IR scsibus / target / lun
of the CD/DVD/BluRay-Recorder. Communication on 
.I SunOS
is done with the SCSI general driver
.B scg.
Other operating systems are using a library simulation of this driver.
Possible syntax is:
.B dev=
.IR scsibus , target , lun
or
.B dev=
.IR target , lun .
In the latter case, the CD/DVD/BluRay-Recorder has to be connected to the default 
SCSI bus of the machine.
.IR Scsibus ,
.I target 
and 
.I 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:
.B dev=
.IR devicename : scsibus , target , lun
or
.B dev=
.IR 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
.B dev=
.IR devicename : @
or
.B dev=
.IR devicename : @ , lun
may be used instead of
.B dev=
.IR devicename : scsibus , target , lun .
.sp
.B \h'-2m'Remote SCSI addressing
.br
To access remote SCSI devices, you need to prepend the SCSI device name by
a remote device indicator. The remote device indicator is either
.BI REMOTE: user@host:
or
.BI REMOTE: host:
A valid remote SCSI device name may be:
.BI REMOTE: user@host:
to allow remote SCSI bus scanning or
.BI REMOTE: user@host:1,0,0
to access the SCSI device at 
.I host
connected to SCSI bus # 1,target 0, lun 0.
In order to allow remote access to a specific
.IR host ,
the
.BR rscsi (1)
program needs to be present and configured on the
.IR host .
.sp
.B \h'-2m'Alternate SCSI transports
.br
.B Cdrecord
is completely based on 
.B SCSI
commands but this is no problem as all CD/DVD/BluRay writers
ever made use
.B SCSI
commands for the communication. Even
.B ATAPI
drives are just
.B SCSI
drives that inherently use the 
.I "ATA packet interface
as
.B 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
.B SCSI
commands via a single unique user interface.
.sp
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
.B USCSI: 
or
.BR ATAPI: .
To get a list of supported transport layers for your platform, use 
.B dev=
.IR HELP :
.sp
.B \h'-2m'Portability Background
.br
To make 
.B readcd
portable to all \s-2UNIX\s0 platforms, the syntax
.B dev=
.IR 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 
.IR scsibus , target , lun .
.sp
.I Scsibus 
0 is the default SCSI bus on the machine. Watch the boot messages for more 
information or look into 
.B /var/adm/messages 
for more information about the SCSI configuration of your machine.
If you have problems to figure out what values for 
.IR scsibus , target , lun
should be used, try the 
.B \-scanbus
option of 
.B readcd
described below.
.sp
.B \h'-2m'Using logical names for devices
.br
If no 
.I dev
option is present, 
.B readcd
will try to get the device from the 
.B CDR_DEVICE
environment.
.sp
If a file /etc/default/cdrecord exists, and
if the argument to the
.B dev=
option
or the
.B 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).
.sp
.B \h'-2m'Autotarget Mode
.br
If no 
.B dev=
option 
and no
.B CDR_DEVICE
environment
is present, or if it
only contains a transport specifyer but no address notation,
.B readcd
tries to scan the SCSI address space for CD-ROM drives.
If exactly one is found, this is used by default.
.TP
.BI debug= "#, " \-d
Set the misc debug value to # (with debug=#) or increment
the misc debug level by one (with \-d). If you specify
.I \-dd,
this equals to 
.BI debug= 2.
This may help to find problems while opening a driver for libscg.
as well as with sector sizes and sector types.
Using
.B \-debug
slows down the process and may be the reason for a buffer underrun.
.TP
.BR kdebug= "#, " kd= #
Tell the 
.BR scg -driver
to modify the kernel debug value while SCSI commands are running.
.TP
.B \-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: 
.B "bus * 100 + target
.TP
.BI scgopts= list
A comma separated list of SCSI options that are handled by libscg.
The implemented options may be uptated indepentendly from applications.
Currently, one option:
.B ignore\-resid
is supported to work around a Linux kernel bug.
.TP
.BR \-silent ", " \-s
Do not print out a status report for failed SCSI commands.
.TP
.BI timeout= #
Set the default SCSI command timeout value to 
.IR # " 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 
.I timeout 
option is present, a default timeout of 40 seconds is used.
.TP
.BR ts= #
Set the maximum transfer size for a single SCSI command to #.
The syntax for the 
.B ts=
option is the same as for cdrecord fs=# or sdd bs=#.
.sp
If no 
.B ts=
option has been specified,
.B 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
.B ts=
option.
.TP
.B \-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.
.B \-VV
will show data buffer content in addition.
Using
.B \-V
or
.B \-VV
slows down the process.
.SH EXAMPLES
.PP
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.
.PP
To read the complete media from a CD-ROM writing the data to the file
.IR cdimage.raw :
.PP
    readcd dev=2,0 f=cdimage.raw
.PP
To read sectors from range 150 ... 10000 from a CD-ROM writing the data to the file
.IR cdimage.raw :
.PP
    readcd dev=2,0 sectors=150-10000 f=cdimage.raw
.PP
To write the data from the file
.I cdimage.raw
(e.g. a filesystem image from 
.BR mkisofs )
to a DVD-RAM, call:
.PP
    readcd dev=2,0 \-w f=cdimage.raw

.SH ENVIRONMENT
.TP
.B RSH
If the 
.B RSH
environment is present, the remote connection will not be created via
.BR rcmd (3)
but by calling the program pointed to by
.BR RSH .
Use e.g. 
.BR RSH= /usr/bin/ssh
to create a secure shell connection.
.sp
Note that this forces 
.B cdrecord
to create a pipe to the 
.B rsh(1)
program and disallows
.B 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 
.B root
initiated
.B rcmd(3)
connection.
.TP
.B RSCSI
If the 
.B RSCSI
environment is present, the remote SCSI server will not be the program
.B /opt/schily/sbin/rscsi
but the program pointed to by
.BR 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.
.SH EXIT STATUS
The following exit codes are used:
.TP
.B 0
No error appeared.
.TP
.B \-1
A specific error appeared. This may be a usage error caused by an illegal command line
or another error with a problem specific error message from
.BR readcd .
.TP
.B \-2
An unspecified error appeared during the process of talking to the drive.
See SCSI error message for more informations. The section
.B DIAGNOSTICS
below contains an explanation on how to read SCSI error messages.
.LP
Note that older operating systems and older shells may not support the full 32 bit
range of the exit code
and mask the value with 0xFF. This results in shortened exit codes in the range
.BR 0 .. 255
where
.B \-1
is mapped to
.BR 255 .

.SH FILES
.SH SEE ALSO
.BR cdrecord (1),
.BR mkisofs (8),
.BR scg (7),
.BR fbk (7),
.BR rcmd (3),
.BR ssh (1).

.SH NOTES
.PP
If you don't want to allow users to become root on your system,
.B readcd
may safely be installed suid root. This allows all users or a group of
users with no root privileges to use 
.B readcd.
.B Readcd
in this case will only allow access to CD-ROM type drives-
To give all user access to use 
.B readcd, 
enter:
.PP
	chown root /usr/local/bin/readcd
.br
	chmod 4711 /usr/local/bin/readcd
.PP
To give a restricted group of users access to 
.B readcd
enter:
.PP
	chown root /usr/local/bin/readcd
.br
	chgrp cdburners /usr/local/bin/readcd
.br
	chmod 4710 /usr/local/bin/readcd
.PP
and add a group 
.I cdburners
on your system.
.PP
Never give write permissions for non root users to the 
.I /dev/scg?
devices unless you would allow anybody to read/write/format
all your disks.
.PP
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.
.PP
When using 
.B readcd
with the 
.B "Linux SCSI generic driver."
You should note that 
.B 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 
.B Linux
has several flaws:
.TP
\(bu
It cannot see if a SCSI command could not be sent at all.
.TP
\(bu
It cannot get the SCSI status byte. 
.B Readcd
for that reason cannot report failing SCSI commands in some
situations.
.TP
\(bu
It cannot get real DMA count of transfer. 
.B Readcd
cannot tell you if there is an DMA residual count.
.TP
\(bu
It cannot get number of bytes valid in auto sense data.
.B Readcd
cannot tell you if device transfers no sense data at all.
.TP
\(bu
It fetches to few data in auto request sense (CCS/SCSI-2/SCSI-3 needs >= 18).

.SH DIAGNOSTICS
.PP
.PP
A typical error message for a SCSI command looks like:
.sp
.RS
.nf
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
.fi
.sp
.RE
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:
.B "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.
.B "fatal error
means that it was not possible to transport the command (i.e. no device present
at the requested SCSI address).
.PP
The second line prints the SCSI command descriptor block for the failed command.
.PP
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.
.PP
The fourth line is a hex dump of the auto request sense information for the 
command.
.PP
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
.I copy
command. If the error message is not directly related to the current command,
the text
.I deferred error
is appended.
.PP
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
.IR scsierrs.c " .
The text is followed by the error value for a field replaceable unit.
.PP
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.
.PP
The eight line reports the timeout set up for this command and the time
that the command really needed to complete.

.SH BUGS

.SH CREDITS

.SH "MAILING LISTS
If you want to actively take part on the development of cdrecord,
you may join the developer mailing list via this URL:
.sp
.B
https://lists.sourceforge.net/lists/listinfo/cdrtools-developers

.SH AUTHOR
.nf
J\*org Schilling
Seestr. 110
D-13353 Berlin
Germany
.fi
.PP
Additional information can be found on:
.br
http://cdrecord.org/private/cdrecord.html
.PP
If you have support questions, send them to:
.PP
.B
cdrtools-support@lists.sourceforge.net
.PP
If you have definitely found a bug, send a mail to:
.PP
.B
cdrtools-developers@lists.sourceforge.net
.br
or
.B
joerg.schilling@fokus.fraunhofer.de
.PP
To subscribe, use:
.PP
.B
https://lists.sourceforge.net/lists/listinfo/cdrtools-developers
.br
or
.B
https://lists.sourceforge.net/lists/listinfo/cdrtools-support
.br
.ne 7
.SH "INTERFACE STABILITY
The interfaces provided by 
.B readcd
are designed for long term stability.
As
.B readcd
depends on interfaces provided by the underlying operating system,
the stability of the interfaces offered by
.B readcd
depends on the interface stability of the OS interfaces. 
Modified interfaces in the OS may enforce modified interfaces
in 
.BR readcd .