=head1 NAME

nbdkit-partition-filter - nbdkit partition filter

=head1 SYNOPSIS

 nbdkit --filter=partition plugin partition=PART [plugin-args...]

=head1 DESCRIPTION

C<nbdkit-partition-filter> is a filter that limits requests to a
single partition within a disk image that is served by another plugin.

Partition numbers are specified by the required C<partition>
parameter, and count from 1.

This works like the C<qemu-nbd -P> option.

The opposite of this filter is L<nbdkit-partitioning-plugin(1)> which
adds a virtual partition table to a file or files.

=head1 PARAMETERS

=over 4

=item B<partition=>PART

The partition number to serve, counting from 1.

This parameter is required.

=item B<partition-sectorsize=>SECTOR_SIZE

The default for this parameter is chosen according to the minimum block
size advertised by the underlying device.  If it is 512 or 4K, then the
sector size is set to that.  If the underlying device does not advertise
a minimum block size, or it is something other than 512 or 4K, the
default is 512 bytes.

The user may specify 512 or 4096 as the sector size manually via config.

However set, this parameter instructs the partition table
logic to treat the underlying storage as having the
indicated sector size.  This is important for MBR
and GPT logic using LBA (logical block addressing).

=back

=head1 EXAMPLE

F<disk.img> is a partitioned disk image (eg. a virtual machine disk
image).  To serve the first partition only use:

 nbdkit --filter=partition file disk.img partition=1

=head1 FILES

=over 4

=item F<$filterdir/nbdkit-partition-filter.so>

The filter.

Use C<nbdkit --dump-config> to find the location of C<$filterdir>.

=back

=head1 VERSION

C<nbdkit-partition-filter> first appeared in nbdkit 1.2.

=head1 SEE ALSO

L<nbdkit(1)>,
L<nbdkit-file-plugin(1)>,
L<nbdkit-filter(3)>,
L<nbdkit-map-filter(1)>,
L<nbdkit-offset-filter(1)>,
L<nbdkit-partitioning-plugin(1)>,
L<nbdkit-protect-filter(1)>,
L<nbdkit-truncate-filter(1)>,
L<parted(8)>.

=head1 AUTHORS

Eric Blake

Richard W.M. Jones

=head1 COPYRIGHT

Copyright Red Hat
