Manual Pages  — FDREAD

The fdread utility will always read an entire floppy medium, and write its contents to the respective output file. Unlike other tools like dd(1), fdread automatically uses a read block size that is more efficient than reading single blocks (usually one track of data at a time), but falls back to reading single floppy sectors in case of an input/output error occurred, in order to obtain as much valid data as possible. While fdread is working, kernel error reporting for floppy errors is turned off, so the console and/or syslog are not flooded with kernel error messages.

The fdread utility accepts the following options:

-q
	Turn on quiet mode. By default, the medium parameters of the device are being written to standard error output, progress will be indicated by the approximate number of kilobytes read so far, and errors will be printed out in detail, including the information about the location of recovered data in the output. In quiet mode, none of these messages will be generated.
-r
	Enable error recovery. By default, fdread stops after the first unrecovered read error, much like dd(1) does. In recovery mode, however, one of two recovery actions will be taken: If the error was a CRC error in the data field, the kernel is told to ignore the error, and data are transferred to the output file anyway. Note that this will cause the erroneous data to be included in the output file! Still, this is the best recovery action that can be taken at all. All other errors are really fatal (usually, the FDC did not find the sector ID fields), thus a dummy block with fill bytes will be included in the output file. Unless operating in quiet mode, the action taken and the location of the error in the output file will be displayed.
-d device
	Specify the input floppy device, defaulting to /dev/fd0. The parameter device must be a valid floppy disk device.
-f fillbyte
	Value of the fill byte used for dummy blocks in the output file in recovery mode. Defaults to ‘0xf0’. (Mnemonic: "foo.") The value can be specified using the usual C language notation of the number base.
-o file
	Specify the output file to be file. By default, the data will be written to standard output.
-I numsects
	Read numsects sector ID fields, and write out their contents to standard output. Each sector ID field contains recorded values for the cylinder number (‘C’), the head number (‘H’), the record number (sector number starting with 1) (‘R’), and the sector shift value (0 = 128 bytes, 1 = 256 bytes, 2 = 512 bytes, 3 = 1024 bytes) (‘N’). The -I option is mutually exclusive with all other options except -d device and -t trackno.
-t trackno
	Specify the track number (cylinder number * number of heads + head number) to read the sector ID fields from; only allowed together with the -I numsects option.

The command appeared in FreeBSD 5.0 .

No attempt beyond the floppy error retry mechanism of fdc(4) is made in order to see whether bad sectors could still be read without errors by trying multiple times.

Bits that are (no longer) available on the floppy medium cannot be guessed by fdread.