dvdisaster Version 0.55 |
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Command syntaxActions. dvdisaster needs to be called with at least one action specified either in long form (--read) or just by the beginning letter (-r):
Device and filenames. These options do also have a long form (--device) and a first letter abbreviation (-d). They are used to change the pre-selected drive and file names.
Other Options. These less frequently used options are only available in the long form unless noted otherwise.
Actions.--scan [n-m]: Scan medium for read errorsReads every medium sector and prints the number of unreadable sectors when finished. It is possible to limit the scan to a certain range of sectors. Sector counting starts with 0; "end" refers to the last sector. The given interval is inclusive; 0-100 will read 101 sectors. Do not use white space in the abbreviated form between the "-s" and the interval: dvdisaster -s0-100 # reads sectors 0 to 100 dvdisaster --scan 0-100 # long form dvdisaster --scan 3000-end # reads from sector 3000 until the end of medium --read [n-m]: Read the medium image to hard disc Creates a medium image on the hard disc. If the image file is already present, only sectors missing in the image will be re-read. This allows for completing the image in several reading passes, and optionally to employ different drives in each of them. It is possible to limit the scan to a certain range of sectors. Sector counting starts with 0; "end" refers to the last sector. The given interval is inclusive; 0-100 will read 101 sectors. Do not use white space in the abbreviated form between the "-r" and the interval: dvdisaster -r0-100 # reads sectors 0 to 100 dvdisaster --read 0-100 # long form dvdisaster --read 3000-end # reads from sector 3000 until the end of medium --create: Create the error correction file Creates the error correction file for an image.
Try to fix an image using the error correction file. If you do not succeed in repairing all sectors during the first pass, attempt to re-read some of the still missing sectors with another --read pass, and try fixing the image again.
--test: Test whether image and error correction files match This action simply checks whether the image and error correction files match (belong to the same medium), and whether their internal check sums are correct. See also topic 3.3 in the Questions and Answers. --unlink: Delete the image file at program exit This function deletes the image file if all preceeding actions were successful.
Devices and file names.--device <drive>: Select a driveThe preset is "/dev/cdrom" for Linux. Under Windows, the first CD/DVD drive (according to the drive letter order) is pre-selected. Linux: dvdisaster supports drives which are accessible through the Linux uniform CD-ROM driver and which are MMC3 compliant. These are particularly ATAPI drives attached to the symbolic devices /dev/hd* and SCSI drives using the symbolic devices /dev/scd*. External drives using other bus systems (like USB, IEEE 1394) usually also appear as SCSI devices. Accessing ATAPI drives using the ide-scsi module is not recommended, but possible since these devices are usually available under the /dev/scd* interface. The general SCSI driver sg (/dev/sg*) is not supported. This should not be a problem since the respective drives are also available using the /dev/scd* or /dev/sr* devices. Windows: dvdisaster supports local drives implementing the MMC3 standard and which are referenced through a drive letter in the system. --prefix <prefix>: Prefix for image and error correction files The preset is "medium"; the image and error correction files will automatically receive the endings ".img" and ".ecc". --image <file name>: Name of image file The preset is "medium.img"; the specified file name will be used exactly (without appending a suffix) for the image file. --eccfile <file name>: Name of error correction file The preset is "medium.ecc"; the specified file name will be used exactly (without appending a suffix) for the error correction file. --list: shows drives available under ASPI This option lists all CD/DVD drives which are accessible through the ASPI layer of Windows:
Per default, dvdisaster only uses ASPI when accessing the drive via SPTI is not possible. Usage of the ASPI layer can be forced by specifying the drive by its number rather than by its letter. To read in a disc using ASPI and the "MYDRIVE" unit from the above example, you would therefore enter:
Other Options.--cache-size <size in MB>: Specify the cache sizedvdisaster optimizes access to the image file by maintaining its own cache during the calculation of error correction files. The cache size can be between 1 and 512 MB. The preset is 32MB, which should be suitable for most systems. This option is only effective during the --create action. --dao: Assumes "disk at once" medium Media written in "TAO" ("track at once") mode contain two sectors with pseudo read errors at the end. By default these two errors are ignored by dvdisaster. If you are extremely unlucky to have a "DAO" ("disc at once") medium with exactly one or two real read errors at the end, use the "--dao" option to have these read errors handled correctly. -j / --jump <number of sectors>: Skip sectors after a read error The given number of sectors will be skipped when an unreadable sector is encountered. This saves some time when reading defective media and reduces mechanical wear on the drive. The number of skipped sectors must be a multiple of 16. The following settings are of particular interest:
-n / --redundancy: Set error correction code redundancy The redundancy specifies the percentage of correctable errors per ECC block. Since read errors are not evenly distributed over all ECC blocks, a redundancy of x percent does not imply that also the same percentage of defective sectors can be recovered. Usually the number of recoverable media sectors is lower. For the Reed-Solomon code used in dvdisaster the redundancy also gives an approximation of the error correction file size: As an example, when encoding a 4GB image using a 25% redundancy the resulting error correction file will be about 1GB in size. The are several ways of specifying the redundancy:
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Copyright 2004,2005 Carsten Gnörlich. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. |
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