1nbd_shutdown(3) LIBNBD nbd_shutdown(3)
2
6 nbd_shutdown - disconnect from the NBD server
7
9 #include <libnbd.h>
10 int nbd_shutdown (struct nbd_handle *h, uint32_t flags);
12
14 Issue the disconnect command to the NBD server. This is a nice way to
15 tell the server we are going away, but from the client's point of view
16 has no advantage over abruptly closing the connection (see
17 nbd_close(3)).
18 This function works whether or not the handle is ready for transmission
20 of commands, and as such does not take a "flags" parameter. If more
21 fine-grained control is needed, see nbd_aio_disconnect(3).
22 The "flags" parameter must be 0 for now (it exists for future NBD
24 protocol extensions).
25
27 If the call is successful the function returns 0.
28
30 On error "-1" is returned.
31 Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
33 of the error.
34
36 The handle must be connected and finished handshaking with the server,
37 otherwise this call will return an error.
38
40 This function first appeared in libnbd 1.0.
41 If you need to test if this function is available at compile time check
43 if the following macro is defined:
44 #define LIBNBD_HAVE_NBD_SHUTDOWN 1
46
48 This example is also available as examples/reads-and-writes.c in the
49 libnbd source code.
50 /* This example shows how to do synchronous reads
52 * and writes randomly over the first megabyte of an
53 * NBD server. Note this will destroy any existing
54 * content on the NBD server.
55 *
56 * To test it with nbdkit and a RAM disk:
57 *
58 * nbdkit -U - memory 1M \
59 * --run './simple-reads-and-writes $unixsocket'
60 */
61 #include <stdio.h>
63 #include <stdlib.h>
64 #include <inttypes.h>
65 #include <assert.h>
66 #include <time.h>
67 #include <libnbd.h>
69 int
71 main (int argc, char *argv[])
72 {
73 struct nbd_handle *nbd;
74 char buf[512];
75 size_t i;
76 int64_t exportsize;
77 uint64_t offset;
78 srand (time (NULL));
80 if (argc != 2) {
82 fprintf (stderr, "%s socket\n", argv[0]);
83 exit (EXIT_FAILURE);
84 }
85 /* Create the libnbd handle. */
87 nbd = nbd_create ();
88 if (nbd == NULL) {
89 fprintf (stderr, "%s\n", nbd_get_error ());
90 exit (EXIT_FAILURE);
91 }
92 /* Connect to the NBD server over a
94 * Unix domain socket.
95 */
96 if (nbd_connect_unix (nbd, argv[1]) == -1) {
97 fprintf (stderr, "%s\n", nbd_get_error ());
98 exit (EXIT_FAILURE);
99 }
100 /* Get the size of the disk and check
102 * it's large enough.
103 */
104 exportsize = nbd_get_size (nbd);
105 if (exportsize == -1) {
106 fprintf (stderr, "%s\n", nbd_get_error ());
107 exit (EXIT_FAILURE);
108 }
109 assert (exportsize >= sizeof buf);
110 /* Check that the server is writable. */
112 if (nbd_is_read_only (nbd) == 1) {
113 fprintf (stderr, "%s: "
114 "error: this NBD export is read-only\n",
115 argv[0]);
116 exit (EXIT_FAILURE);
117 }
118 for (i = 0; i < sizeof buf; ++i)
120 buf[i] = rand ();
121 /* 1000 writes. */
123 for (i = 0; i < 1000; ++i) {
124 offset = rand () % (exportsize - sizeof buf);
125 if (nbd_pwrite (nbd, buf, sizeof buf,
127 offset, 0) == -1) {
128 fprintf (stderr, "%s\n", nbd_get_error ());
129 exit (EXIT_FAILURE);
130 }
131 }
132 /* 1000 reads and writes. */
134 for (i = 0; i < 1000; ++i) {
135 offset = rand () % (exportsize - sizeof buf);
136 if (nbd_pread (nbd, buf, sizeof buf,
137 offset, 0) == -1) {
138 fprintf (stderr, "%s\n", nbd_get_error ());
139 exit (EXIT_FAILURE);
140 }
141 offset = rand () % (exportsize - sizeof buf);
143 if (nbd_pwrite (nbd, buf, sizeof buf,
144 offset, 0) == -1) {
145 fprintf (stderr, "%s\n", nbd_get_error ());
146 exit (EXIT_FAILURE);
147 }
148 }
149 /* Sends a graceful shutdown to the server. */
151 if (nbd_shutdown (nbd, 0) == -1) {
152 fprintf (stderr, "%s\n", nbd_get_error ());
153 exit (EXIT_FAILURE);
154 }
155 nbd_close (nbd);
157 exit (EXIT_SUCCESS);
159 }
160
162 nbd_aio_disconnect(3), nbd_close(3), nbd_create(3), libnbd(3).
163
165 Eric Blake
166 Richard W.M. Jones
168
170 Copyright (C) 2019 Red Hat Inc.
171
173 This library is free software; you can redistribute it and/or modify it
174 under the terms of the GNU Lesser General Public License as published
175 by the Free Software Foundation; either version 2 of the License, or
176 (at your option) any later version.
177 This library is distributed in the hope that it will be useful, but
179 WITHOUT ANY WARRANTY; without even the implied warranty of
180 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
181 Lesser General Public License for more details.
182 You should have received a copy of the GNU Lesser General Public
184 License along with this library; if not, write to the Free Software
185 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
186 02110-1301 USA
187libnbd-1.3.7 2020-04-23 nbd_shutdown(3)