nbd_clear_meta_contexts - Man Page

reset the list of requested meta contexts


 #include <libnbd.h>

 int nbd_clear_meta_contexts (
       struct nbd_handle *h


During connection libnbd can negotiate zero or more metadata contexts with the server.  Metadata contexts are features (such as "base:allocation") which describe information returned by the nbd_block_status_64(3) command (for "base:allocation" this is whether blocks of data are allocated, zero or sparse).

This command resets the list of meta contexts to request back to an empty list, for re-population by further use of nbd_add_meta_context(3).  It is primarily useful when option negotiation mode is selected (see nbd_set_opt_mode(3)), for altering the list of attempted contexts between subsequent export queries.

Return Value

If the call is successful the function returns 0.


On error -1 is returned.

Refer to "ERROR HANDLING" in libnbd(3) for how to get further details of the error.

The following parameters must not be NULL: h. For more information see "Non-NULL parameters" in libnbd(3).

Handle State

The handle must be newly created, or negotiating, otherwise this call will return an error.


This function first appeared in libnbd 1.6.

If you need to test if this function is available at compile time check if the following macro is defined:


See Also

nbd_add_meta_context(3), nbd_block_status_64(3), nbd_can_meta_context(3), nbd_create(3), nbd_get_meta_context(3), nbd_get_nr_meta_contexts(3), nbd_set_opt_mode(3), libnbd(3).


Eric Blake

Richard W.M. Jones


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

Referenced By

libnbd(3), libnbd-release-notes-1.6(1), NBD(3), nbd_add_meta_context(3), nbd_get_meta_context(3), nbd_get_nr_meta_contexts(3), nbd_opt_list_meta_context(3), nbd_opt_set_meta_context(3).

2023-09-08 libnbd-1.17.5