nbdkit-map-filter - remap disk blocks
nbdkit --filter=map PLUGIN [map=START-END:DEST [map=...]]
[map-size=SIZE]nbdkit-map-filter is an nbdkit(1) filter which can remap parts of the underlying plugin, such as moving a sector or partition. To select part of a disk, use nbdkit-offset-filter(1) instead. To select a partition, use nbdkit-partition-filter(1). This filter cannot change the size of the disk, use nbdkit-truncate-filter(1) to do that.
Using two map parameters, this remaps the first sector (bytes 0-511) on to the second sector (starting at 512), and the second sector (bytes 512-1023) on to the first sector (0).
nbdkit --filter=map file orig.img map=0-511:512 map=512-1023:0Map bytes in the range START to END (inclusive) to DEST in the underlying plugin. The destination range ends at:
DEST_END = DEST+END-STARTThis means that when the byte at offset START is read or written (or any other operation such as trim), the request is redirected to the byte at offset DEST in the underlying plugin, and so on for the following bytes up to and including offset END which is mapped to DEST_END.
DEST through to DEST_END must exist in the underlying plugin. Attempts to map requests beyond the end of the underlying plugin will return I/O errors.
You can give this parameter multiple times. If overlapping ranges are described then the first matching range on the command line takes precedence. There is an implicit 1-1 mapping covering parts of the disk not covered by explicit map parameters.
If you have a large number of mappings, consider using the nbdkit @PATH parameter to read them from an external file (see "@PATH" in nbdkit(1)).
If this parameter is set, the size of the disk is set to SIZE. Note if SIZE is larger than the underlying plugin then you must map areas of the disk beyond the plugin up to SIZE, otherwise accesses will return I/O errors.
If this parameter is not set, the size of the underlying plugin is used.
The filter.
Use nbdkit --dump-config to find the location of $filterdir.
nbdkit-map-filter first appeared in nbdkit 1.46.
nbdkit(1), nbdkit-extentlist-filter(1), nbdkit-offset-filter(1), nbdkit-partition-filter(1), nbdkit-protect-filter(1), nbdkit-truncate-filter(1), nbdkit-filter(3).
Richard W.M. Jones
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