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Diffstat (limited to 'docs/tools/qemu-storage-daemon.rst')
| -rw-r--r-- | docs/tools/qemu-storage-daemon.rst | 68 |
1 files changed, 61 insertions, 7 deletions
diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst index c05b3d3811..086493ebb3 100644 --- a/docs/tools/qemu-storage-daemon.rst +++ b/docs/tools/qemu-storage-daemon.rst @@ -69,7 +69,7 @@ Standard options: a description of character device properties. A common character device definition configures a UNIX domain socket:: - --chardev socket,id=char1,path=/tmp/qmp.sock,server=on,wait=off + --chardev socket,id=char1,path=/var/run/qsd-qmp.sock,server=on,wait=off .. option:: --export [type=]nbd,id=<id>,node-name=<node-name>[,name=<export-name>][,writable=on|off][,bitmap=<name>] --export [type=]vhost-user-blk,id=<id>,node-name=<node-name>,addr.type=unix,addr.path=<socket-path>[,writable=on|off][,logical-block-size=<block-size>][,num-queues=<num-queues>] @@ -80,8 +80,9 @@ Standard options: requests for modifying data (the default is off). The ``nbd`` export type requires ``--nbd-server`` (see below). ``name`` is - the NBD export name. ``bitmap`` is the name of a dirty bitmap reachable from - the block node, so the NBD client can use NBD_OPT_SET_META_CONTEXT with the + the NBD export name (if not specified, it defaults to the given + ``node-name``). ``bitmap`` is the name of a dirty bitmap reachable from the + block node, so the NBD client can use NBD_OPT_SET_META_CONTEXT with the metadata context name "qemu:dirty-bitmap:BITMAP" to inspect the bitmap. The ``vhost-user-blk`` export type takes a vhost-user socket address on which @@ -101,14 +102,17 @@ Standard options: .. option:: --nbd-server addr.type=inet,addr.host=<host>,addr.port=<port>[,tls-creds=<id>][,tls-authz=<id>][,max-connections=<n>] --nbd-server addr.type=unix,addr.path=<path>[,tls-creds=<id>][,tls-authz=<id>][,max-connections=<n>] + --nbd-server addr.type=fd,addr.str=<fd>[,tls-creds=<id>][,tls-authz=<id>][,max-connections=<n>] is a server for NBD exports. Both TCP and UNIX domain sockets are supported. - TLS encryption can be configured using ``--object`` tls-creds-* and authz-* - secrets (see below). + A listen socket can be provided via file descriptor passing (see Examples + below). TLS encryption can be configured using ``--object`` tls-creds-* and + authz-* secrets (see below). - To configure an NBD server on UNIX domain socket path ``/tmp/nbd.sock``:: + To configure an NBD server on UNIX domain socket path + ``/var/run/qsd-nbd.sock``:: - --nbd-server addr.type=unix,addr.path=/tmp/nbd.sock + --nbd-server addr.type=unix,addr.path=/var/run/qsd-nbd.sock .. option:: --object help --object <type>,help @@ -118,6 +122,20 @@ Standard options: List object properties with ``<type>,help``. See the :manpage:`qemu(1)` manual page for a description of the object properties. +.. option:: --pidfile PATH + + is the path to a file where the daemon writes its pid. This allows scripts to + stop the daemon by sending a signal:: + + $ kill -SIGTERM $(<path/to/qsd.pid) + + A file lock is applied to the file so only one instance of the daemon can run + with a given pid file path. The daemon unlinks its pid file when terminating. + + The pid file is written after chardevs, exports, and NBD servers have been + created but before accepting connections. The daemon has started successfully + when the pid file is written and clients may begin connecting. + Examples -------- Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute @@ -127,6 +145,42 @@ QMP commands:: --chardev socket,path=qmp.sock,server=on,wait=off,id=char1 \ --monitor chardev=char1 +Launch the daemon from Python with a QMP monitor socket using file descriptor +passing so there is no need to busy wait for the QMP monitor to become +available:: + + #!/usr/bin/env python3 + import subprocess + import socket + + sock_path = '/var/run/qmp.sock' + + with socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) as listen_sock: + listen_sock.bind(sock_path) + listen_sock.listen() + + fd = listen_sock.fileno() + + subprocess.Popen( + ['qemu-storage-daemon', + '--chardev', f'socket,fd={fd},server=on,id=char1', + '--monitor', 'chardev=char1'], + pass_fds=[fd], + ) + + # listen_sock was automatically closed when leaving the 'with' statement + # body. If the daemon process terminated early then the following connect() + # will fail with "Connection refused" because no process has the listen + # socket open anymore. Launch errors can be detected this way. + + qmp_sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) + qmp_sock.connect(sock_path) + ...QMP interaction... + +The same socket spawning approach also works with the ``--nbd-server +addr.type=fd,addr.str=<fd>`` and ``--export +type=vhost-user-blk,addr.type=fd,addr.str=<fd>`` options. + Export raw image file ``disk.img`` over NBD UNIX domain socket ``nbd.sock``:: $ qemu-storage-daemon \ |