nbdcopy(1) LIBNBD nbdcopy(1) (NAME) nbdcopy - NBD (SYNOPSIS) nbdcopy [--allocated] [--blkhash=DIGEST] [--blkhash-file=FILE] [-C N|--connections=N] [--destination-is-zero|--target-is-zero] [--flush] [--no-extents] [-p|--progress|--progress=FD] [--queue-size=N] [--request-size=N] [-R N|--requests=N] [-S N|--sparse=N] [--synchronous] [-T N|--threads=N] [-v|--verbose] SOURCE DESTINATION SOURCE, DESTINATION := - | FILE | DEVICE | NBD-URI | [ CMD ARGS ... ] DESTINATION += null: nbdcopy --help nbdcopy -V|--version (EXAMPLES) nbdcopy nbd://example.com local.img NBD "example.com" local.img . nbdcopy nbd://example.com - | file - NBD "example.com" file(1) () . "-" (stdout) ( file ). nbdinfo(1) NBD . nbdcopy -p /dev/sdX "nbd+unix:///?socket=/tmp/unixsock" "/dev/sdX" NBD (Unix domain socket) /tmp/unixsock . -p . nbdcopy nbd://server1 nbd://server2 NBD NBD . nbdcopy nbd://server1 nbd://server2 --blkhash NBD NBD blkhash ( ) . nbdcopy -- [ qemu-nbd -r -f qcow2 https://example.com/disk.qcow2 ] - qemu-nbd(8) "https://example.com/disk.qcow2" ("-") (raw) . "--" qemu-nbd nbdcopy . cat disk1 disk2 | nbdcopy -- - [ qemu-nbd -f qcow2 output.qcow2 ] raw qcow2 output.qcow2. . nbdcopy nbd://server null: NBD ( null). NBD nbdcopy . (DESCRIPTION) nbdcopy / NBD . NBD NBD / (stdin/stdout) . NBD . ( "/dev/cdrom") "-" (stdin) (stdout) . NBD URI NBD ( "nbd://localhost") . NBD libnbd . qemu-nbd(8) nbdkit(1) NBD nbdcopy . "null:" . "qemu-img convert" qemu-img(1) . (OPTIONS) --help . --allocated nbdcopy ( hole) . : (extent) ( --no-extents ) ( -S ). --allocated nbdcopy . --blkhash --blkhash=md5 --blkhash=md5/SIZE --blkhash=sha1 --blkhash=sha1/SIZE --blkhash=sha256 --blkhash=sha256/SIZE --blkhash=sha512 --blkhash=sha512/SIZE blkhash . Blkhash (https://gitlab.com/nirs/blkhash) . cksum(1) sha256sum(1) . nbdcopy . (digest) "md5" "sha1" "sha256" () "sha512" . "64k" () . --blkhash sha256/64k . blkhash : nbdcopy --blkhash -- disk.raw null: qcow2 : nbdcopy --blkhash -- [ qemu-nbd -f qcow2 disk.qcow2 ] null: --blkhash-file=FILE --blkhash blkhash. (stdout) . -C N --connections=N NBD (" " multi-conn). NBD nbdcopy multi-conn . NBD multi-conn nbdcopy . --destination-is-zero --target-is-zero . nbdcopy . . nbddiscard(1) nbdzero(1) . --target-is-zero qemu-img(1) . --flush (Flush) nbdcopy. --no-extents nbdcopy (extent) . nbdcopy . : NBD . -p --progress . --progress=FD "FD" ( ) . nbdcopy "N/100\n" ( N ) . nbdcopy : exec 3>/tmp/progress nbdcopy --progress=3 ... exec 3>&- --queue-size=N . 16 MiB 256k NBD . --request-size . --request-size=N . NBD 32 MiB . -R N --requests=N (in flight) NBD. -S N --sparse=N N () () . -S 0 . ( ). --synchronous (Synchronous) API (" ") libnbd(3). NBD . / stdio . -T N --threads=N N (thread) . . --threads=0 --threads=1 . -v --verbose (Verbose). libnbd ( nbd_set_debug(3) ) . -V --version . (MULTI-CONN, THREADS, REQUESTS IN FLIGHT) --connections --threads --requests . . / stdio --synchronous nbdcopy . --connections=N multi-conn NBD ( "Multi-conn" libnbd(3) ) N NBD ( NBD) . . NBD multi-conn . nbdkit(1) multi-conn . nbdinfo(1) NBD multi-conn . NBD multi-conn --connections . NBD multi-conn . multi-conn . NBD ( "[ ... ]") multi-conn . --threads=N nbdcopy N ( ). nbdcopy NBD . --requests=N (in flight) NBD . NBD multi-conn . . nbdcopy . --synchronous . NBD (RUNNING NBD SERVER AS A SUBPROCESS) URI NBD : nbdcopy -- [ CMD ARGS ... ] ... systemd qemu-nbd(8) nbdkit(1) ( nbd_connect_systemd_socket_activation(3) ). "[" "]" . "--" NBD nbdcopy . . nbdcopy . . nbdcopy -- [ qemu-nbd -f qcow2 disk.qcow2 ] - | hexdump -C qemu-nbd(8) . disk.qcow2 NBD nbdcopy . nbdcopy ("-") hexdump(1) . ( nbddump(1) ) nbdcopy -- [ qemu-nbd -f qcow2 disk.qcow2 ] [ nbdkit memory 1G ] : qemu-nbd(8) nbdkit(1) . qcow2 raw RAM (nbdkit-memory-plugin(1)). nbdcopy RAM . (SEE ALSO) libnbd(3) nbddiscard(1) nbddump(1) nbdfuse(1) nbdinfo(1) nbdsh(1) nbdublk(1) nbdzero(1) nbdkit(1) qemu-img(1) https://gitlab.com/nirs/blkhash blksum(1). (AUTHORS) Richard W.M. Jones (COPYRIGHT) Copyright Red Hat (LICENSE) << >> (GNU LGPL) << >> -- ( ) -- / . . << >> . << >> : Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA libnbd-1.24.3 2026-07-16 nbdcopy(1)