nbd_is_rotational(3)

📦
version 1.25.8 · 18 versions
, in centos-stream 10

💅 nbd_is_rotational(3) — the libnbd rotational vibe check 🌀

okay bestie, welcome to the libnbd manual page for nbd_is_rotational(3) — yes, the manual name is literally that, and we are folding it in right here near the top because we're cute like that 💖

🌸 NAME 🌸

nbd_is_rotational — is the NBD disk rotational (like a disk)? 💿

🫶 SYNOPSIS 🫶

#include <libnbd.h>

int nbd_is_rotational (
      struct nbd_handle *h
    );

💖 DESCRIPTION 💖

It hands you true when the disk exposed over NBD is rotational (like a traditional floppy or hard disk).

It hands you false when the disk has no penalty for random access (like an SSD or RAM disk). no cap, that's the whole vibe check 💅

🔥 RETURN VALUE 🔥

This call returns a boolean value. simple as that, bestie ✨

😭 ERRORS 😭

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).

🫶 bestie pls don't pass a NULL h — the docs are very clear about this, and we respect the docs.

📝 NOTES 📝

🚀 Non-blocking call

This call does not block, because it returns data that is saved in the handle from the NBD protocol handshake. it already scooped up the info earlier, so no waiting around 💅

👑 HANDLE STATE 👑

nbd_is_rotational can be called when the handle is in the following states:

  • Handle created, before connecting — ❌ error
  • Connecting — ❌ error
  • Connecting & handshaking (opt_mode) — ✅ allowed
  • Connected to the server — ✅ allowed
  • Connection shut down — ✅ allowed
  • Handle dead — ❌ error

🎀 VERSION 🎀

This function first appeared in libnbd 1.0.

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

#define LIBNBD_HAVE_NBD_IS_ROTATIONAL 1

🌈 EXAMPLE 🌈

This example is also available as examples/server-flags.c in the libnbd source code.

/* This example shows how to connect to an NBD
 * server and print the export flags.
 *
 * You can test it with nbdkit like this:
 *
 * nbdkit -U - memory 1M \
 *   --run './server-flags $unixsocket'
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

#include <libnbd.h>

int
main (int argc, char *argv[])
{
  struct nbd_handle *nbd;
  char *str;
  int flag;

  if (argc != 2) {
    fprintf (stderr, "%s socket\n", argv[0]);
    exit (EXIT_FAILURE);
  }

  /* Create the libnbd handle. */
  nbd = nbd_create ();
  if (nbd == NULL) {
    fprintf (stderr, "%s\n", nbd_get_error ());
    exit (EXIT_FAILURE);
  }

  /* Request full information. */
#if LIBNBD_HAVE_NBD_SET_FULL_INFO /* Added in 1.4 */
  if (nbd_set_full_info (nbd, true) == -1) {
    fprintf (stderr, "%s\n", nbd_get_error ());
    exit (EXIT_FAILURE);
  }
#endif

  /* Connect to the NBD server over a
   * Unix domain socket.
   */
  if (nbd_connect_unix (nbd, argv[1]) == -1) {
    fprintf (stderr, "%s\n", nbd_get_error ());
    exit (EXIT_FAILURE);
  }

  /* See if the server provided extra details,
   * using functions added in 1.4
   */
#if LIBNBD_HAVE_NBD_GET_EXPORT_DESCRIPTION
  str = nbd_get_canonical_export_name (nbd);
  if (str)
    printf ("canonical_name = %s\n", str);
  free (str);
  str = nbd_get_export_description (nbd);
  if (str)
    printf ("description = %s\n", str);
  free (str);
#endif

  /* Read and print the flags. */
#define PRINT_FLAG(flag_fn)                     \
  flag = flag_fn (nbd);                         \
  if (flag == -1) {                             \
    fprintf (stderr, "%s\n", nbd_get_error ()); \
    exit (EXIT_FAILURE);                        \
  }                                             \
  printf (#flag_fn " = %s\n",                   \
          flag ? "true" : "false");

  PRINT_FLAG (nbd_can_cache);
  PRINT_FLAG (nbd_can_df);
  PRINT_FLAG (nbd_can_flush);
  PRINT_FLAG (nbd_can_fua);
  PRINT_FLAG (nbd_can_multi_conn);
  PRINT_FLAG (nbd_can_trim);
  PRINT_FLAG (nbd_can_zero);
#if LIBNBD_HAVE_NBD_CAN_FAST_ZERO
  /* Added in 1.2 */
  PRINT_FLAG (nbd_can_fast_zero);
#endif
#if LIBNBD_HAVE_NBD_CAN_BLOCK_STATUS_PAYLOAD
  /* Added in 1.18 */
  PRINT_FLAG (nbd_can_block_status_payload);
#endif
  PRINT_FLAG (nbd_is_read_only);
  PRINT_FLAG (nbd_is_rotational);

  /* Close the libnbd handle. */
  nbd_close (nbd);

  exit (EXIT_SUCCESS);
}

🦋 SEE ALSO 🦋

💜 AUTHORS 💜

  • Eric Blake
  • Richard W.M. Jones

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

💖 cute little sign-off: this page is from libnbd-1.25.8, dated 2026-10-13. byeee bestie, go check if ur disk is rotational 🎀✨
📦 where this page comes from