nbddiscard(1)                       LIBNBD                       nbddiscard(1)


NAME
       nbddiscard, nbdzero - discard or zero all data on a Network Block
       Device

SYNOPSIS
        nbddiscard [-c|--check] [-z|--zero] [--fast-zero]
                   [-q|--quiet] [-v|--verbose] [-y|--yes]
                   [-o|--offset OFFSET] [-l|--length LENGTH] NBD-URI

        nbddiscard -V|--version

        nbddiscard -h|--help

        nbdzero [-c|--check] [--fast-zero]
                [-q|--quiet] [-v|--verbose] [-y|--yes]
                [-o|--offset OFFSET] [-l|--length LENGTH] NBD-URI

        nbdzero -V|--version

        nbdzero -h|--help

DESCRIPTION
       nbddiscard discards all data on a Network Block Device (NBD) endpoint.
       If supported, this frees up the backing storage and makes the device
       completely sparse.  For example, if an NBD server is running locally on
       port 10809 you could do:

        $ nbddiscard nbd://localhost
        PERMANENTLY ERASE everything on nbd://localhost bytes 0 - 1073741823
        (y/N)? y

       nbdzero is the same, but the data is replaced by allocated, zeroed
       blocks.

       All data in the discarded or zeroed region is PERMANENTLY ERASED.

       For information about NBD URIs, see nbd_connect_uri(3).

OPTIONS
       -c
       --check
           Rather than modify the disk, merely check whether it is already
           sparse, or with -z that it already reads as zero.

       --fast-zero
           Attempt fast zero (see nbd_can_fast_zero(3)), which implies --zero.

           Not all servers support the fast zero flag, but those that do
           promise that an attempted fast zero operation will either complete
           more quickly than explicitly writing zeroes to the image, or that
           it will immediately fail because the operation is not inherently
           faster.

       -h
       --help
           Display brief command line help and exit.

       -l LENGTH
       --length LENGTH
           Instead of discarding to the end of the disk, discard only length
           bytes.  You can use the normal suffixes like "K", "M" etc.

       -o OFFSET
       --offset OFFSET
           Instead of starting from the beginning of the disk, start at the
           given offset.  You can use the normal suffixes like "K", "M" etc.

       -q
       --quiet
           Quiet mode, do not print any warnings.

       -v
       --verbose
           Enable verbose libnbd messages.  This has the same effect as
           setting the environment variable "LIBNBD_DEBUG=1"

       -V
       --version
           Display the package name and version and exit.

       -y
       --yes
           Assume yes to all questions.  This will proceed straight to erasing
           your data.  Use this in scripts to avoid interactivity.

       -z
       --zero
           Zero, instead of discarding.  nbdzero is just nbddiscard with -z.

SEE ALSO
       libnbd(3), libnbd-python(3), nbd_connect_uri(3), nbdcopy(1),
       nbddump(1), nbdfuse(1), nbdinfo(1), nbdsh(1), nbdublk(1),
       blkdiscard(8), qemu-img(1).

AUTHORS
       Richard W.M. Jones

COPYRIGHT
       Copyright Red Hat

LICENSE
       This library is free software; you can redistribute it and/or modify it
       under the terms of the GNU Lesser General Public License as published
       by the Free Software Foundation; either version 2 of the License, or
       (at your option) any later version.

       This library is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
       Lesser General Public License for more details.

       You should have received a copy of the GNU Lesser General Public
       License along with this library; if not, write to the Free Software
       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
       02110-1301 USA

libnbd-1.24.0                     2025-12-16                     nbddiscard(1)