212 lines
9.1 KiB
Plaintext
212 lines
9.1 KiB
Plaintext
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cdrskin Wiki - plain text copy
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[[Image(source:/libburn/trunk/cdrskin/doener_150x200_tr.gif)]] [http://en.wikipedia.org/wiki/D%C3%B6ner_kebab Doener]
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'''cdrskin is the cdrecord compatibility middleware of libburn.'''
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Its paragon, cdrecord, is a powerful GPL'ed burn program included in Joerg
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Schilling's cdrtools. cdrskin strives to be a second source for the services
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traditionally provided by cdrecord. Currently it does CD-R and CD-RW.
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Its future ability to burn DVD media depends on the development of libburn.
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cdrskin does not contain any bytes copied from cdrecord's sources.
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Many bytes have been copied from the message output of cdrecord
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runs, though. The most comprehensive technical overview of cdrskin
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can be found in [http://libburnia.pykix.org/browser/libburn/trunk/cdrskin/README?format=txt cdrskin/README].
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About libburn API for burning CD: http://libburnia-api.pykix.org
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Appending sessions to an unclosed CD is restricted to write mode TAO.
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(Users who have a burner which succeeds with a follow-up session via
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cdrecord -sao : please contact us.)
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cdrskin does not provide DVD burning yet. See advise to use dvd+rw-tools
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at the end of this text.
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About the command line options of cdrskin:
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There are two families of options: cdrecord-compatible ones and options
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which are specific to cdrskin. The latter are mostly used to configure
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cdrskin for its task to emulate cdrecord. There are some, nevertheless,
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which provide rather exotic unique features of cdrskin.
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The cdrecord-compatible options are listed in the output of
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{{{
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cdrskin -help
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}}}
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where the option "help" has *one* dash.
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For these options you may expect program behavior that is roughly the
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same as described in original man 1 cdrecord .
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Online: http://cdrecord.berlios.de/old/private/man/cdrecord-2.0.html
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The cdrskin-specific options are listed by
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{{{
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cdrskin --help
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}}}
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where the option "help" has *two* dashes.
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Those have no man page yet. Some are very experimental and should only be
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used in coordination with the libburnia developer team.
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Some are of general user interest, though:
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--devices allows the sysadmin to scan the system for possible drives
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and displays their detected properties.
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The drives are listed one per line, with fields:
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libburn-drive-number, sysadmin-device-file, permissions, vendor, type
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{{{
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0 dev='/dev/sg0' rwrw-- : 'HL-DT-ST' 'DVDRAM GSA-4082B'
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}}}
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This feature is valuable since cdrskin -scanbus will not give you
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the device file name and its current permissions.
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cdrskin will accept of course the proposed dev= option as address
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for any usage of the drive.
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Different from cdrecord, cdrskin is intended to be run without special
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privileges, i.e. no superuser setuid. It is intended that the sysadmin
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controls drive accessability by rw-permissions of the drive rather than
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by x-permission of the burn binary. To be usable with cdrskin, the drive
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has to offer both, r- and w-permission.
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fifo_start_at=<num> is a throughput enhancer for unsteady data streams
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like they are produced by a compressing archiver program when piping to
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CD on-the-fly. It makes better use of the general property of a FIFO
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buffer to transport surplus bandwidth into the future. Yep. A time machine.
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One-way, i fear.
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FIFO originally was introduced by cdrecord's author Joerg Schilling in order
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to protect mediocre burner hardware from suffering buffer underruns
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and thus producing misburns (at 1x speed on CD-R media at the price of a
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DVD-RAM nowadays). This purpose would not justify a fifo any more -
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given the limited life time of burners and the seamless underrun protection
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of contemporary consumer drives.
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With an unsteady data stream the task of the buffer is to soak up peak
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performance and to release it steadily at the drive's maximum speed.
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The larger the buffer the more reserves can be built up and the longer
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input drought can be compensated.
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Original cdrecord has the historical property, though, to first wait until
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the buffer is completely filled. Best practice for fighting drive
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underruns, of course.
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With a very fat fs=# buffer (128 MB for 12x CD is not unrealistic) this
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can cause a big delay until burning finally starts and takes its due time.
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fifo_start_at=<num> makes cdrskin start burning after the given number of bytes
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is read rather than waiting for the FIFO to be completely full resp. the data
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stream to end. It risks a few drive buffer underruns at the beginning of burn
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- but modern drives stand this.
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Usage examples:
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{{{
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cdrskin ... fs=128m fifo_start_at=20m ...
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cdrskin ... fifo_start_at=0 ...
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}}}
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Note: no FIFO can give you better average throughput than the average
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throughput of the data source and the throughput of the burner.
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It can be used, though, to bring the effective throughput very close
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to the theoretical limit. Especially with high speed media.
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--no_rc allows you to surely ban influence from systemwide or user specific
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default settings of cdrskin. Possible locations for such settings:
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/etc/default/cdrskin
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/etc/opt/cdrskin/rc
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/etc/cdrskin/cdrskin.conf
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$HOME/.cdrskinrc
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tao_to_sao_tsize=<num> allows the - actually unsupported - cdrecord option
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-tao and defines a default track size to be used if - as custom with -tao -
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no option tsize=# is given.
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Since -tao is supported in cdrskin-0.2.6 the TAO-to-SAO workaround has become
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quite obsolete. Nevertheless, tao_to_sao_tsize= allows to preset a default
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size for SAO mode which is in effect only if no track size is available.
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As in general with cdrskin tsize=# the data source does not have to provide
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the full annouced amount of data. Missing data will be padded up by 0-bytes.
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Surplus data is supposed to cause an error, though. The burn will then
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be a failure in any way.
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dev_translation=<sep><from><sep><to> may be needed to foist cdrskin to
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frontend programs of cdrecord which do *not* ask cdrecord -scanbus but
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which make own assumptions and guesses about cdrecord's device addresses.
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Normally, cdrskin understands all addresses which are suitable for cdrecord
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under Linux. See cdrskin/README, "Pseudo-SCSI Adresses".
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This option is mainly for (yet unknown) exotic configurations or very
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stubborn frontend programs.
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If a frontend refuses to work with cdrskin, look into the error protocol
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of that frontend, look at the output of a run of cdrskin --devices and give
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cdrskin the necessary hint.
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Example: Your frontend insists in using "0,0,0" and --devices reported
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dev='/dev/hdc' resp. cdrskin dev=ATA -scanbus reported "1,0,0" then this
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would be the appropriate translation:
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{{{
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dev_translation=+0,0,0+/dev/hdc
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}}}
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The "+" character is a separator to be choosen by you.
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Currently i am not aware of the need to choose any other than "+"
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unless you get playful with custom translations like
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{{{
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dev_translation=-"cd+dvd"-1,0,0
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}}}
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See http://scdbackup.sourceforge.net/k3b_on_cdrskin.html
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for an illustrated example with K3b 0.10 .
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DVD advise:
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For burning of DVD media the cdrskin project currently advises to use
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Andy Polyakov's dvd+rw-tools which despite their historic name burn
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for me on above burner: DVD+RW, DVD+R, DVD-RW, DVD-R .
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http://fy.chalmers.se/~appro/linux/DVD+RW/tools
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They are not compatible or related to cdrecord resp. cdrecord-ProDVD
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(now obsoleted by original source cdrtools cdrecord with identical
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capabilities besides the license key).
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If there is sincere and well motivated interest, the cdrskin project could try
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to employ growisofs as DVD burning engine. The cdrskin project would prefer to
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wait for DVD support being included in libburn, though.
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A very limited and specialized cdrecord-compatibility wrapper for growisofs
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serves in my project scdbackup. It is not overly hard to make one that serves
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some very few fixed use cases.
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To my knowledge, Linux kernels 2.6 do write to DVD+RW via block devices as
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they would write to a traditional tape device. Try old tape archiver
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commands with addresses like /dev/sr0 or /dev/hdc rather than /dev/mt0 .
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I have heard rumors that DVD-RW in mode "restricted overwrite" would be
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block device ready, too. My burner is not a real friend of DVD-RW and
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in an experiment the burn worked fine - but the result was not identical
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to the stream sent to the device. I had similar failure with DVD-RAM, too.
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Beware of the impact of a slow block device on overall system i/o buffering.
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It is wise to curb its input to a speed which it is able to deliver to media.
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Else your i/o dedicated RAM might buffer a big amount of stream data.
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