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48 utility reads floppy disks. Effective read blocking based on the track
49 size is performed, and floppy-specific error recovery of otherwise
50 bad blocks can be enabled.
53 will always read an entire floppy medium, and write its contents to
54 the respective output file. Unlike other tools like
57 automatically uses a read block size that is more efficient than
58 reading single blocks (usually one track of data at a time), but
59 falls back to reading single floppy sectors in case of an input/output
60 error occurred, in order to obtain as much valid data as possible.
63 is working, kernel error reporting for floppy errors is turned off, so
64 the console and/or syslog are not flooded with kernel error messages.
68 utility accepts the following options:
69 .Bl -tag -width indent
71 Turn on quiet mode. By default, the medium parameters of the device
72 are being written to standard error output, progress will be indicated
73 by the approximate number of kilobytes read so far, and errors will be
74 printed out in detail, including the information about the location of
75 recovered data in the output. In quiet mode, none of these messages
78 Enable error recovery. By default,
80 stops after the first unrecovered read error, much like
82 does. In recovery mode, however, one of two recovery actions will be
86 If the error was a CRC error in the data field, the
87 kernel is told to ignore the error, and data are transferred to the
90 Note that this will cause the erroneous data
91 to be included in the output file!
93 Still, this is the best recovery action that can be taken at all.
95 All other errors are really fatal (usually, the FDC didn't find the
96 sector ID fields), thus a dummy block with fill
97 bytes will be included in the output file.
100 Unless operating in quiet mode, the action taken and the location of
101 the error in the output file will be displayed.
103 Specify the input floppy device, defaulting to
107 must be a valid floppy disk device.
109 Value of the fill byte used for dummy blocks in the output file in
110 recovery mode. Defaults to
114 The value can be specified using the usual C language notation of
117 Specify the output file to be
119 By default, the data will be written to standard output.
123 sector ID fields, and write out their contents to standard output.
124 Each sector ID field contains recorded values for the cylinder number
128 the record number (sector number starting with 1)
131 .Em sector shift value
132 (0 = 128 bytes, 1 = 256 bytes, 2 = 512 bytes, 3 = 1024 bytes)
136 option is mutually exclusive with all other options except
141 Specify the track number (cylinder number * number of heads + head
142 number) to read the sector ID fields from; only allowed together with
148 .Bl -tag -width /dev/fd0
150 Default device to read from.
154 sets the exit value according to
156 In recovery mode, the exit value will be set to
158 if any error occurred during processing (even in quiet mode).
160 Unless running in quiet mode, upon encountering an error, the status
161 of the floppy disc controller (FDC) will be printed out, both in
162 hexadecimal form, followed by a textual description that translates
163 those values into a human-readable form for the most common error
164 cases that can happen in a PC environment.
166 The FDC error status includes the three FDC status registers
171 as well as the location of the error (physical cylinder, head, and sector
173 .Dq sector shift value ,
174 respectively). See the manual for the NE765 or compatible for details
175 about the status register contents.
177 The FDC's status is then examined to determine whether the error is
178 deemed to be recoverable. If error recovery was requested, the
179 location of the bad block in the output file is indicated by its
180 (hexadecimal) bounds. Also, a summary line indicating the total number
181 of transfer errors will be printed before exiting.
191 utility was written mainly to provide a means of recovering at least some of
192 the data on bad media, and to obviate the need to invoke
194 with too many hard to memorize options that might be useful to handle
197 The command appeared in
200 Program and man page by
203 Concurrent traffic on the second floppy drive located at the same FDC
204 will make error recovery attempts pointless, since the FDC status
205 obtained after a read error occurred cannot be guaranteed to actually
206 belong to the erroneous transfer. Thus using option
210 is the only active drive on that controller.
212 No attempt beyond the floppy error retry mechanism of
214 is made in order to see whether bad sectors could still be read
215 without errors by trying multiple times.
217 Bits that are (no longer) available on the floppy medium cannot be