READCD(1) Schily´s USER COMMANDS READCD(1)NAMEreadcd - read or write data Compact Discs
SYNOPSISreadcd 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 corect syntax for the device is: dev= devi‐
cename:scsibus,target,lun or dev= devicename:target,lun. If the name
of the device node that has been specified on such a system referres to
exactly one SCSI device, a shorthand in the form dev= devicename:@ or
dev= devicename:@,lun may be used instead of dev= devicename:scsi‐
bus,target,lun.
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 intercative mode. Select a primary function and then follow the
instructions.
-version
Print version information and exit.
-v Increment the level of general verbosity by one.
-V Increment the verbose level in respect of SCSI command transport
by one. This helps to debug problems during the writing
process, that occur in the drive. 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 and may be the reason for a
buffer underrun.
-w Switch to write mode. If this option is not present, readcd
reads from the specified device.
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.
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
FILESSEE ALSOcdrecord(1), mkisofs(1), scg(7), fbk(7).
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 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 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)
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.
BUGSCREDITSMAILING 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.gmd.de/usr/schilling/cdrecord.html
Mail bugs and suggestions to:
joerg@schily.isdn.cs.tu-berlin.de or js@cs.tu-berlin.de or
schilling@fokus.gmd.de
Joerg Schilling Version 1.8.1 READCD(1)
