9bd11f9638
Reported-by: Eric Blake <eblake@redhat.com> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Message-Id: <20220107105420.395011-2-f4bug@amsat.org> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
224 lines
8.5 KiB
ReStructuredText
224 lines
8.5 KiB
ReStructuredText
===================
|
|
QEMU Storage Daemon
|
|
===================
|
|
|
|
Synopsis
|
|
--------
|
|
|
|
**qemu-storage-daemon** [options]
|
|
|
|
Description
|
|
-----------
|
|
|
|
``qemu-storage-daemon`` provides disk image functionality from QEMU,
|
|
``qemu-img``, and ``qemu-nbd`` in a long-running process controlled via QMP
|
|
commands without running a virtual machine.
|
|
It can export disk images, run block job operations, and
|
|
perform other disk-related operations. The daemon is controlled via a QMP
|
|
monitor and initial configuration from the command-line.
|
|
|
|
The daemon offers the following subset of QEMU features:
|
|
|
|
* Block nodes
|
|
* Block jobs
|
|
* Block exports
|
|
* Throttle groups
|
|
* Character devices
|
|
* Crypto and secrets
|
|
* QMP
|
|
* IOThreads
|
|
|
|
Commands can be sent over a QEMU Monitor Protocol (QMP) connection. See the
|
|
:manpage:`qemu-storage-daemon-qmp-ref(7)` manual page for a description of the
|
|
commands.
|
|
|
|
The daemon runs until it is stopped using the ``quit`` QMP command or
|
|
SIGINT/SIGHUP/SIGTERM.
|
|
|
|
**Warning:** Never modify images in use by a running virtual machine or any
|
|
other process; this may destroy the image. Also, be aware that querying an
|
|
image that is being modified by another process may encounter inconsistent
|
|
state.
|
|
|
|
Options
|
|
-------
|
|
|
|
.. program:: qemu-storage-daemon
|
|
|
|
Standard options:
|
|
|
|
.. option:: -h, --help
|
|
|
|
Display help and exit
|
|
|
|
.. option:: -V, --version
|
|
|
|
Display version information and exit
|
|
|
|
.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
|
|
|
|
.. include:: ../qemu-option-trace.rst.inc
|
|
|
|
.. option:: --blockdev BLOCKDEVDEF
|
|
|
|
is a block node definition. See the :manpage:`qemu(1)` manual page for a
|
|
description of block node properties and the :manpage:`qemu-block-drivers(7)`
|
|
manual page for a description of driver-specific parameters.
|
|
|
|
.. option:: --chardev CHARDEVDEF
|
|
|
|
is a character device definition. See the :manpage:`qemu(1)` manual page for
|
|
a description of character device properties. A common character device
|
|
definition configures a UNIX domain socket::
|
|
|
|
--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>]
|
|
--export [type=]vhost-user-blk,id=<id>,node-name=<node-name>,addr.type=fd,addr.str=<fd>[,writable=on|off][,logical-block-size=<block-size>][,num-queues=<num-queues>]
|
|
--export [type=]fuse,id=<id>,node-name=<node-name>,mountpoint=<file>[,growable=on|off][,writable=on|off]
|
|
|
|
is a block export definition. ``node-name`` is the block node that should be
|
|
exported. ``writable`` determines whether or not the export allows write
|
|
requests for modifying data (the default is off).
|
|
|
|
The ``nbd`` export type requires ``--nbd-server`` (see below). ``name`` is
|
|
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
|
|
it accept incoming connections. Both
|
|
``addr.type=unix,addr.path=<socket-path>`` for UNIX domain sockets and
|
|
``addr.type=fd,addr.str=<fd>`` for file descriptor passing are supported.
|
|
``logical-block-size`` sets the logical block size in bytes (the default is
|
|
512). ``num-queues`` sets the number of virtqueues (the default is 1).
|
|
|
|
The ``fuse`` export type takes a mount point, which must be a regular file,
|
|
on which to export the given block node. That file will not be changed, it
|
|
will just appear to have the block node's content while the export is active
|
|
(very much like mounting a filesystem on a directory does not change what the
|
|
directory contains, it only shows a different content while the filesystem is
|
|
mounted). Consequently, applications that have opened the given file before
|
|
the export became active will continue to see its original content. If
|
|
``growable`` is set, writes after the end of the exported file will grow the
|
|
block node to fit.
|
|
|
|
.. option:: --monitor MONITORDEF
|
|
|
|
is a QMP monitor definition. See the :manpage:`qemu(1)` manual page for
|
|
a description of QMP monitor properties. A common QMP monitor definition
|
|
configures a monitor on character device ``char1``::
|
|
|
|
--monitor chardev=char1
|
|
|
|
.. 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.
|
|
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
|
|
``/var/run/qsd-nbd.sock``::
|
|
|
|
--nbd-server addr.type=unix,addr.path=/var/run/qsd-nbd.sock
|
|
|
|
.. option:: --object help
|
|
--object <type>,help
|
|
--object <type>[,<property>=<value>...]
|
|
|
|
is a QEMU user creatable object definition. List object types with ``help``.
|
|
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
|
|
QMP commands::
|
|
|
|
$ qemu-storage-daemon \
|
|
--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 \
|
|
--blockdev driver=file,node-name=disk,filename=disk.img \
|
|
--nbd-server addr.type=unix,addr.path=nbd.sock \
|
|
--export type=nbd,id=export,node-name=disk,writable=on
|
|
|
|
Export a qcow2 image file ``disk.qcow2`` as a vhost-user-blk device over UNIX
|
|
domain socket ``vhost-user-blk.sock``::
|
|
|
|
$ qemu-storage-daemon \
|
|
--blockdev driver=file,node-name=file,filename=disk.qcow2 \
|
|
--blockdev driver=qcow2,node-name=qcow2,file=file \
|
|
--export type=vhost-user-blk,id=export,addr.type=unix,addr.path=vhost-user-blk.sock,node-name=qcow2
|
|
|
|
Export a qcow2 image file ``disk.qcow2`` via FUSE on itself, so the disk image
|
|
file will then appear as a raw image::
|
|
|
|
$ qemu-storage-daemon \
|
|
--blockdev driver=file,node-name=file,filename=disk.qcow2 \
|
|
--blockdev driver=qcow2,node-name=qcow2,file=file \
|
|
--export type=fuse,id=export,node-name=qcow2,mountpoint=disk.qcow2,writable=on
|
|
|
|
See also
|
|
--------
|
|
|
|
:manpage:`qemu(1)`, :manpage:`qemu-block-drivers(7)`, :manpage:`qemu-storage-daemon-qmp-ref(7)`
|