diff options
| -rw-r--r-- | Makefile | 8 | ||||
| -rw-r--r-- | block-nbd.c | 194 | ||||
| -rw-r--r-- | block.c | 1 | ||||
| -rw-r--r-- | block.h | 1 | ||||
| -rw-r--r-- | nbd.c | 211 | ||||
| -rw-r--r-- | nbd.h | 26 | ||||
| -rw-r--r-- | qemu-doc.texi | 35 | ||||
| -rw-r--r-- | qemu-nbd.c | 10 | ||||
| -rw-r--r-- | qemu-nbd.texi | 2 |
9 files changed, 412 insertions, 76 deletions
@@ -42,7 +42,7 @@ recurse-all: $(SUBDIR_RULES) BLOCK_OBJS=cutils.o qemu-malloc.o BLOCK_OBJS+=block-cow.o block-qcow.o aes.o block-vmdk.o block-cloop.o BLOCK_OBJS+=block-dmg.o block-bochs.o block-vpc.o block-vvfat.o -BLOCK_OBJS+=block-qcow2.o block-parallels.o +BLOCK_OBJS+=block-qcow2.o block-parallels.o block-nbd.o ###################################################################### # libqemu_common.a: Target independent part of system emulation. The @@ -50,7 +50,7 @@ BLOCK_OBJS+=block-qcow2.o block-parallels.o # system emulation, i.e. a single QEMU executable should support all # CPUs and machines. -OBJS=$(BLOCK_OBJS) +OBJS=nbd.o $(BLOCK_OBJS) OBJS+=readline.o console.o OBJS+=block.o @@ -159,7 +159,7 @@ libqemu_user.a: $(USER_OBJS) rm -f $@ $(AR) rcs $@ $(USER_OBJS) -QEMU_IMG_BLOCK_OBJS = $(BLOCK_OBJS) +QEMU_IMG_BLOCK_OBJS = nbd.o $(BLOCK_OBJS) ifdef CONFIG_WIN32 QEMU_IMG_BLOCK_OBJS += qemu-img-block-raw-win32.o else @@ -180,7 +180,7 @@ qemu-img-%.o: %.c qemu-nbd-%.o: %.c $(CC) $(CFLAGS) $(CPPFLAGS) -DQEMU_NBD -c -o $@ $< -qemu-nbd$(EXESUF): qemu-nbd.o nbd.o qemu-img-block.o \ +qemu-nbd$(EXESUF): qemu-nbd.o qemu-nbd-nbd.o qemu-img-block.o \ osdep.o qemu-nbd-block-raw-posix.o $(BLOCK_OBJS) $(CC) $(LDFLAGS) -o $@ $^ -lz $(LIBS) diff --git a/block-nbd.c b/block-nbd.c new file mode 100644 index 000000000..f35005015 --- /dev/null +++ b/block-nbd.c @@ -0,0 +1,194 @@ +/* + * QEMU Block driver for NBD + * + * Copyright (C) 2008 Bull S.A.S. + * Author: Laurent Vivier <Laurent.Vivier@bull;net> + * + * Some parts: + * Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws> + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#include "qemu-common.h" +#include "nbd.h" + +#include <sys/types.h> +#include <unistd.h> +#include <sys/socket.h> +#include <sys/un.h> +#include <netinet/in.h> +#include <arpa/inet.h> +#include <pthread.h> + +typedef struct BDRVNBDState { + int sock; + off_t size; + size_t blocksize; +} BDRVNBDState; + +static int nbd_open(BlockDriverState *bs, const char* filename, int flags) +{ + BDRVNBDState *s = bs->opaque; + const char *host; + const char *unixpath; + int sock; + off_t size; + size_t blocksize; + int ret; + + if ((flags & BDRV_O_CREAT)) + return -EINVAL; + + if (!strstart(filename, "nbd:", &host)) + return -EINVAL; + + if (strstart(host, "unix:", &unixpath)) { + + if (unixpath[0] != '/') + return -EINVAL; + + sock = unix_socket_outgoing(unixpath); + + } else { + uint16_t port; + char *p, *r; + char hostname[128]; + + pstrcpy(hostname, 128, host); + + p = strchr(hostname, ':'); + if (p == NULL) + return -EINVAL; + + *p = '\0'; + p++; + + port = strtol(p, &r, 0); + if (r == p) + return -EINVAL; + sock = tcp_socket_outgoing(hostname, port); + } + + if (sock == -1) + return -errno; + + ret = nbd_receive_negotiate(sock, &size, &blocksize); + if (ret == -1) + return -errno; + + s->sock = sock; + s->size = size; + s->blocksize = blocksize; + + return 0; +} + +static int nbd_read(BlockDriverState *bs, int64_t sector_num, + uint8_t *buf, int nb_sectors) +{ + BDRVNBDState *s = bs->opaque; + struct nbd_request request; + struct nbd_reply reply; + + request.type = NBD_CMD_READ; + request.handle = (uint64_t)(intptr_t)bs; + request.from = sector_num * 512;; + request.len = nb_sectors * 512; + + if (nbd_send_request(s->sock, &request) == -1) + return -errno; + + if (nbd_receive_reply(s->sock, &reply) == -1) + return -errno; + + if (reply.error !=0) + return -reply.error; + + if (reply.handle != request.handle) + return -EIO; + + if (nbd_wr_sync(s->sock, buf, request.len, 1) != request.len) + return -EIO; + + return 0; +} + +static int nbd_write(BlockDriverState *bs, int64_t sector_num, + const uint8_t *buf, int nb_sectors) +{ + BDRVNBDState *s = bs->opaque; + struct nbd_request request; + struct nbd_reply reply; + + request.type = NBD_CMD_WRITE; + request.handle = (uint64_t)(intptr_t)bs; + request.from = sector_num * 512;; + request.len = nb_sectors * 512; + + if (nbd_send_request(s->sock, &request) == -1) + return -errno; + + if (nbd_wr_sync(s->sock, (uint8_t*)buf, request.len, 0) != request.len) + return -EIO; + + if (nbd_receive_reply(s->sock, &reply) == -1) + return -errno; + + if (reply.error !=0) + return -reply.error; + + if (reply.handle != request.handle) + return -EIO; + + return 0; +} + +static void nbd_close(BlockDriverState *bs) +{ + BDRVNBDState *s = bs->opaque; + struct nbd_request request; + + request.type = NBD_CMD_DISC; + request.handle = (uint64_t)(intptr_t)bs; + request.from = 0; + request.len = 0; + nbd_send_request(s->sock, &request); + + close(s->sock); +} + +static int64_t nbd_getlength(BlockDriverState *bs) +{ + BDRVNBDState *s = bs->opaque; + + return s->size; +} + +BlockDriver bdrv_nbd = { + "nbd", + sizeof(BDRVNBDState), + NULL, /* no probe for protocols */ + nbd_open, + nbd_read, + nbd_write, + nbd_close, + .bdrv_getlength = nbd_getlength, + .protocol_name = "nbd", +}; @@ -1332,6 +1332,7 @@ void bdrv_init(void) bdrv_register(&bdrv_vvfat); bdrv_register(&bdrv_qcow2); bdrv_register(&bdrv_parallels); + bdrv_register(&bdrv_nbd); } void *qemu_aio_get(BlockDriverState *bs, BlockDriverCompletionFunc *cb, @@ -16,6 +16,7 @@ extern BlockDriver bdrv_vpc; extern BlockDriver bdrv_vvfat; extern BlockDriver bdrv_qcow2; extern BlockDriver bdrv_parallels; +extern BlockDriver bdrv_nbd; typedef struct BlockDriverInfo { /* in bytes, 0 if irrelevant */ @@ -1,4 +1,4 @@ -/*\ +/* * Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws> * * Network Block Device @@ -15,7 +15,7 @@ * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA -\*/ + */ #include "nbd.h" @@ -31,17 +31,21 @@ #include <arpa/inet.h> #include <netdb.h> +#if defined(QEMU_NBD) extern int verbose; +#else +static int verbose = 0; +#endif + +#define TRACE(msg, ...) do { \ + if (verbose) LOG(msg, ## __VA_ARGS__); \ +} while(0) #define LOG(msg, ...) do { \ fprintf(stderr, "%s:%s():L%d: " msg "\n", \ __FILE__, __FUNCTION__, __LINE__, ## __VA_ARGS__); \ } while(0) -#define TRACE(msg, ...) do { \ - if (verbose) LOG(msg, ## __VA_ARGS__); \ -} while(0) - /* This is all part of the "official" NBD API */ #define NBD_REQUEST_MAGIC 0x25609513 @@ -59,10 +63,10 @@ extern int verbose; /* That's all folks */ -#define read_sync(fd, buffer, size) wr_sync(fd, buffer, size, true) -#define write_sync(fd, buffer, size) wr_sync(fd, buffer, size, false) +#define read_sync(fd, buffer, size) nbd_wr_sync(fd, buffer, size, true) +#define write_sync(fd, buffer, size) nbd_wr_sync(fd, buffer, size, false) -static size_t wr_sync(int fd, void *buffer, size_t size, bool do_read) +size_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read) { size_t offset = 0; @@ -76,7 +80,7 @@ static size_t wr_sync(int fd, void *buffer, size_t size, bool do_read) } /* recoverable error */ - if (len == -1 && errno == EAGAIN) { + if (len == -1 && (errno == EAGAIN || errno == EINTR)) { continue; } @@ -96,7 +100,7 @@ static size_t wr_sync(int fd, void *buffer, size_t size, bool do_read) return offset; } -static int tcp_socket_outgoing(const char *address, uint16_t port) +int tcp_socket_outgoing(const char *address, uint16_t port) { int s; struct in_addr in; @@ -404,16 +408,31 @@ int nbd_client(int fd, int csock) return ret; } -int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset, - off_t *offset, bool readonly, uint8_t *data, int data_size) +int nbd_send_request(int csock, struct nbd_request *request) { uint8_t buf[4 + 4 + 8 + 8 + 4]; - uint32_t magic; - uint32_t type; - uint64_t from; - uint32_t len; - TRACE("Reading request."); + cpu_to_be32w((uint32_t*)buf, NBD_REQUEST_MAGIC); + cpu_to_be32w((uint32_t*)(buf + 4), request->type); + cpu_to_be64w((uint64_t*)(buf + 8), request->handle); + cpu_to_be64w((uint64_t*)(buf + 16), request->from); + cpu_to_be32w((uint32_t*)(buf + 24), request->len); + + TRACE("Sending request to client"); + + if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) { + LOG("writing to socket failed"); + errno = EINVAL; + return -1; + } + return 0; +} + + +static int nbd_receive_request(int csock, struct nbd_request *request) +{ + uint8_t buf[4 + 4 + 8 + 8 + 4]; + uint32_t magic; if (read_sync(csock, buf, sizeof(buf)) != sizeof(buf)) { LOG("read failed"); @@ -422,97 +441,158 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset, } /* Request - [ 0 .. 3] magic (NBD_REQUEST_MAGIC) - [ 4 .. 7] type (0 == READ, 1 == WRITE) - [ 8 .. 15] handle - [16 .. 23] from - [24 .. 27] len + [ 0 .. 3] magic (NBD_REQUEST_MAGIC) + [ 4 .. 7] type (0 == READ, 1 == WRITE) + [ 8 .. 15] handle + [16 .. 23] from + [24 .. 27] len */ magic = be32_to_cpup((uint32_t*)buf); - type = be32_to_cpup((uint32_t*)(buf + 4)); - from = be64_to_cpup((uint64_t*)(buf + 16)); - len = be32_to_cpup((uint32_t*)(buf + 24)); + request->type = be32_to_cpup((uint32_t*)(buf + 4)); + request->handle = be64_to_cpup((uint64_t*)(buf + 8)); + request->from = be64_to_cpup((uint64_t*)(buf + 16)); + request->len = be32_to_cpup((uint32_t*)(buf + 24)); TRACE("Got request: " "{ magic = 0x%x, .type = %d, from = %" PRIu64" , len = %u }", - magic, type, from, len); - + magic, request->type, request->from, request->len); if (magic != NBD_REQUEST_MAGIC) { LOG("invalid magic (got 0x%x)", magic); errno = EINVAL; return -1; } +} + +int nbd_receive_reply(int csock, struct nbd_reply *reply) +{ + uint8_t buf[4 + 4 + 8]; + uint32_t magic; + + memset(buf, 0xAA, sizeof(buf)); + + if (read_sync(csock, buf, sizeof(buf)) != sizeof(buf)) { + LOG("read failed"); + errno = EINVAL; + return -1; + } + + /* Reply + [ 0 .. 3] magic (NBD_REPLY_MAGIC) + [ 4 .. 7] error (0 == no error) + [ 7 .. 15] handle + */ + + magic = be32_to_cpup((uint32_t*)buf); + reply->error = be32_to_cpup((uint32_t*)(buf + 4)); + reply->handle = be64_to_cpup((uint64_t*)(buf + 8)); + + TRACE("Got reply: " + "{ magic = 0x%x, .error = %d, handle = %" PRIu64" }", + magic, reply->error, reply->handle); + + if (magic != NBD_REPLY_MAGIC) { + LOG("invalid magic (got 0x%x)", magic); + errno = EINVAL; + return -1; + } + return 0; +} + +static int nbd_send_reply(int csock, struct nbd_reply *reply) +{ + uint8_t buf[4 + 4 + 8]; + + /* Reply + [ 0 .. 3] magic (NBD_REPLY_MAGIC) + [ 4 .. 7] error (0 == no error) + [ 7 .. 15] handle + */ + cpu_to_be32w((uint32_t*)buf, NBD_REPLY_MAGIC); + cpu_to_be32w((uint32_t*)(buf + 4), reply->error); + cpu_to_be64w((uint64_t*)(buf + 8), reply->handle); + + TRACE("Sending response to client"); + + if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) { + LOG("writing to socket failed"); + errno = EINVAL; + return -1; + } + return 0; +} - if (len > data_size) { +int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset, + off_t *offset, bool readonly, uint8_t *data, int data_size) +{ + struct nbd_request request; + struct nbd_reply reply; + + TRACE("Reading request."); + + if (nbd_receive_request(csock, &request) == -1) + return -1; + + if (request.len > data_size) { LOG("len (%u) is larger than max len (%u)", - len, data_size); + request.len, data_size); errno = EINVAL; return -1; } - if ((from + len) < from) { + if ((request.from + request.len) < request.from) { LOG("integer overflow detected! " "you're probably being attacked"); errno = EINVAL; return -1; } - if ((from + len) > size) { + if ((request.from + request.len) > size) { LOG("From: %" PRIu64 ", Len: %u, Size: %" PRIu64 ", Offset: %" PRIu64 "\n", - from, len, size, dev_offset); + request.from, request.len, size, dev_offset); LOG("requested operation past EOF--bad client?"); errno = EINVAL; return -1; } - /* Reply - [ 0 .. 3] magic (NBD_REPLY_MAGIC) - [ 4 .. 7] error (0 == no error) - [ 7 .. 15] handle - */ - cpu_to_be32w((uint32_t*)buf, NBD_REPLY_MAGIC); - cpu_to_be32w((uint32_t*)(buf + 4), 0); - TRACE("Decoding type"); - switch (type) { - case 0: + reply.handle = request.handle; + reply.error = 0; + + switch (request.type) { + case NBD_CMD_READ: TRACE("Request type is READ"); - if (bdrv_read(bs, (from + dev_offset) / 512, data, len / 512) == -1) { + if (bdrv_read(bs, (request.from + dev_offset) / 512, data, + request.len / 512) == -1) { LOG("reading from file failed"); errno = EINVAL; return -1; } - *offset += len; - - TRACE("Read %u byte(s)", len); + *offset += request.len; - TRACE("Sending OK response"); + TRACE("Read %u byte(s)", request.len); - if (write_sync(csock, buf, 16) != 16) { - LOG("writing to socket failed"); - errno = EINVAL; + if (nbd_send_reply(csock, &reply) == -1) return -1; - } TRACE("Sending data to client"); - if (write_sync(csock, data, len) != len) { + if (write_sync(csock, data, request.len) != request.len) { LOG("writing to socket failed"); errno = EINVAL; return -1; } break; - case 1: + case NBD_CMD_WRITE: TRACE("Request type is WRITE"); - TRACE("Reading %u byte(s)", len); + TRACE("Reading %u byte(s)", request.len); - if (read_sync(csock, data, len) != len) { + if (read_sync(csock, data, request.len) != request.len) { LOG("reading from socket failed"); errno = EINVAL; return -1; @@ -520,34 +600,29 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset, if (readonly) { TRACE("Server is read-only, return error"); - - cpu_to_be32w((uint32_t*)(buf + 4), 1); + reply.error = 1; } else { TRACE("Writing to device"); - if (bdrv_write(bs, (from + dev_offset) / 512, data, len / 512) == -1) { + if (bdrv_write(bs, (request.from + dev_offset) / 512, + data, request.len / 512) == -1) { LOG("writing to file failed"); errno = EINVAL; return -1; } - *offset += len; + *offset += request.len; } - TRACE("Sending response to client"); - - if (write_sync(csock, buf, 16) != 16) { - LOG("writing to socket failed"); - errno = EINVAL; + if (nbd_send_reply(csock, &reply) == -1) return -1; - } break; - case 2: + case NBD_CMD_DISC: TRACE("Request type is DISCONNECT"); errno = 0; return 1; default: - LOG("invalid request type (%u) received", type); + LOG("invalid request type (%u) received", request.type); errno = EINVAL; return -1; } @@ -1,4 +1,4 @@ -/*\ +/* * Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws> * * Network Block Device @@ -15,7 +15,7 @@ * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA -\*/ + */ #ifndef NBD_H #define NBD_H @@ -26,6 +26,26 @@ #include <qemu-common.h> #include "block_int.h" +struct nbd_request { + uint32_t type; + uint64_t handle; + uint64_t from; + uint32_t len; +}; + +struct nbd_reply { + uint32_t error; + uint64_t handle; +}; + +enum { + NBD_CMD_READ = 0, + NBD_CMD_WRITE = 1, + NBD_CMD_DISC = 2 +}; + +size_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read); +int tcp_socket_outgoing(const char *address, uint16_t port); int tcp_socket_incoming(const char *address, uint16_t port); int unix_socket_outgoing(const char *path); int unix_socket_incoming(const char *path); @@ -33,6 +53,8 @@ int unix_socket_incoming(const char *path); int nbd_negotiate(BlockDriverState *bs, int csock, off_t size); int nbd_receive_negotiate(int csock, off_t *size, size_t *blocksize); int nbd_init(int fd, int csock, off_t size, size_t blocksize); +int nbd_send_request(int csock, struct nbd_request *request); +int nbd_receive_reply(int csock, struct nbd_reply *reply); int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset, off_t *offset, bool readonly, uint8_t *data, int data_size); int nbd_client(int fd, int csock); diff --git a/qemu-doc.texi b/qemu-doc.texi index 3e53d887c..ec02685fc 100644 --- a/qemu-doc.texi +++ b/qemu-doc.texi @@ -1321,6 +1321,7 @@ snapshots. * qemu_nbd_invocation:: qemu-nbd Invocation * host_drives:: Using host drives * disk_images_fat_images:: Virtual FAT disk images +* disk_images_nbd:: NBD access @end menu @node disk_images_quickstart @@ -1503,6 +1504,40 @@ What you should @emph{never} do: @item write to the FAT directory on the host system while accessing it with the guest system. @end itemize +@node disk_images_nbd +@subsection NBD access + +QEMU can access directly to block device exported using the Network Block Device +protocol. + +@example +qemu linux.img -hdb nbd:my_nbd_server.mydomain.org:1024 +@end example + +If the NBD server is located on the same host, you can use an unix socket instead +of an inet socket: + +@example +qemu linux.img -hdb nbd:unix:/tmp/my_socket +@end example + +In this case, the block device must be exported using qemu-nbd: + +@example +qemu-nbd --socket=/tmp/my_socket my_disk.qcow2 +@end example + +The use of qemu-nbd allows to share a disk between several guests: +@example +qemu-nbd --socket=/tmp/my_socket --share=2 my_disk.qcow2 +@end example + +and then you can use it with two guests: +@example +qemu linux1.img -hdb nbd:unix:/tmp/my_socket +qemu linux2.img -hdb nbd:unix:/tmp/my_socket +@end example + @node pcsys_network @section Network emulation diff --git a/qemu-nbd.c b/qemu-nbd.c index 605d4e324..45464a0c8 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -56,6 +56,7 @@ static void usage(const char *name) " -c, --connect=DEV connect FILE to the local NBD device DEV\n" " -d, --disconnect disconnect the specified device\n" " -e, --shared=NUM device can be shared by NUM clients (default '1')\n" +" -t, --persistent don't exit on the last connection\n" " -v, --verbose display extra debugging information\n" " -h, --help display this help and exit\n" " -V, --version output version information and exit\n" @@ -189,7 +190,7 @@ int main(int argc, char **argv) char *device = NULL; char *socket = NULL; char sockpath[128]; - const char *sopt = "hVbo:p:rsnP:c:dvk:e:"; + const char *sopt = "hVbo:p:rsnP:c:dvk:e:t"; struct option lopt[] = { { "help", 0, 0, 'h' }, { "version", 0, 0, 'V' }, @@ -204,6 +205,7 @@ int main(int argc, char **argv) { "snapshot", 0, 0, 's' }, { "nocache", 0, 0, 'n' }, { "shared", 1, 0, 'e' }, + { "persistent", 0, 0, 't' }, { "verbose", 0, 0, 'v' }, { NULL, 0, 0, 0 } }; @@ -222,6 +224,7 @@ int main(int argc, char **argv) int i; int nb_fds = 0; int max_fd; + int persistent = 0; while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) { switch (ch) { @@ -283,6 +286,9 @@ int main(int argc, char **argv) errx(EINVAL, "Shared device number must be greater than 0\n"); } break; + case 't': + persistent = 1; + break; case 'v': verbose = 1; break; @@ -459,7 +465,7 @@ int main(int argc, char **argv) } } } - } while (nb_fds > 1); + } while (persistent || nb_fds > 1); qemu_free(data); close(sharing_fds[0]); diff --git a/qemu-nbd.texi b/qemu-nbd.texi index b196a3471..ff2f20792 100644 --- a/qemu-nbd.texi +++ b/qemu-nbd.texi @@ -36,6 +36,8 @@ Export Qemu disk image using NBD protocol. disconnect the specified device @item -e, --shared=NUM device can be shared by NUM clients (default '1') +@item -t, --persistent + don't exit on the last connection @item -v, --verbose display extra debugging information @item -h, --help |