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docs: standardize book titles to === with overline Documents within a Sphinx manual are separate files and therefore can use different conventions for headings. However, keeping some consistency is useful so that included files are easy to get right. This patch uses a standard heading format for book titles, so that it is obvious when a file sits at the top level toctree of a book or man page. The heading is irrelevant for man pages, but keep it consistent as well. Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-07 15:58:12 +02:00
=====================================
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
QEMU Disk Network Block Device Server
=====================================
Synopsis
--------
**qemu-nbd** [*OPTION*]... *filename*
**qemu-nbd** -L [*OPTION*]...
**qemu-nbd** -d *dev*
Description
-----------
Export a QEMU disk image using the NBD protocol.
Other uses:
- Bind a /dev/nbdX block device to a QEMU server (on Linux).
- As a client to query exports of a remote NBD server.
Options
-------
.. program:: qemu-nbd
*filename* is a disk image filename, or a set of block
driver options if ``--image-opts`` is specified.
*dev* is an NBD device.
.. option:: --object type,id=ID,...props...
Define a new instance of the *type* object class identified by *ID*.
See the :manpage:`qemu(1)` manual page for full details of the properties
supported. The common object types that it makes sense to define are the
``secret`` object, which is used to supply passwords and/or encryption
keys, and the ``tls-creds`` object, which is used to supply TLS
credentials for the qemu-nbd server or client.
.. option:: -p, --port=PORT
TCP port to listen on as a server, or connect to as a client
(default ``10809``).
.. option:: -o, --offset=OFFSET
The offset into the image.
.. option:: -b, --bind=IFACE
The interface to bind to as a server, or connect to as a client
(default ``0.0.0.0``).
.. option:: -k, --socket=PATH
Use a unix socket with path *PATH*.
.. option:: --image-opts
Treat *filename* as a set of image options, instead of a plain
filename. If this flag is specified, the ``-f`` flag should
not be used, instead the :option:`format=` option should be set.
.. option:: -f, --format=FMT
Force the use of the block driver for format *FMT* instead of
auto-detecting.
.. option:: -r, --read-only
Export the disk as read-only.
nbd: Add 'qemu-nbd -A' to expose allocation depth Allow the server to expose an additional metacontext to be requested by savvy clients. qemu-nbd adds a new option -A to expose the qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this can also be set via QMP when using block-export-add. qemu as client is hacked into viewing the key aspects of this new context by abusing the already-experimental x-dirty-bitmap option to collapse all depths greater than 2, which results in a tri-state value visible in the output of 'qemu-img map --output=json' (yes, that means x-dirty-bitmap is now a bit of a misnomer, but I didn't feel like renaming it as it would introduce a needless break of back-compat, even though we make no compat guarantees with x- members): unallocated (depth 0) => "zero":false, "data":true local (depth 1) => "zero":false, "data":false backing (depth 2+) => "zero":true, "data":true libnbd as client is probably a nicer way to get at the information without having to decipher such hacks in qemu as client. ;) Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20201027050556.269064-11-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
2020-10-27 06:05:55 +01:00
.. option:: -A, --allocation-depth
Expose allocation depth information via the
``qemu:allocation-depth`` metadata context accessible through
NBD_OPT_SET_META_CONTEXT.
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
.. option:: -B, --bitmap=NAME
If *filename* has a qcow2 persistent bitmap *NAME*, expose
nbd: Add 'qemu-nbd -A' to expose allocation depth Allow the server to expose an additional metacontext to be requested by savvy clients. qemu-nbd adds a new option -A to expose the qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this can also be set via QMP when using block-export-add. qemu as client is hacked into viewing the key aspects of this new context by abusing the already-experimental x-dirty-bitmap option to collapse all depths greater than 2, which results in a tri-state value visible in the output of 'qemu-img map --output=json' (yes, that means x-dirty-bitmap is now a bit of a misnomer, but I didn't feel like renaming it as it would introduce a needless break of back-compat, even though we make no compat guarantees with x- members): unallocated (depth 0) => "zero":false, "data":true local (depth 1) => "zero":false, "data":false backing (depth 2+) => "zero":true, "data":true libnbd as client is probably a nicer way to get at the information without having to decipher such hacks in qemu as client. ;) Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20201027050556.269064-11-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
2020-10-27 06:05:55 +01:00
that bitmap via the ``qemu:dirty-bitmap:NAME`` metadata context
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
accessible through NBD_OPT_SET_META_CONTEXT.
.. option:: -s, --snapshot
Use *filename* as an external snapshot, create a temporary
file with ``backing_file=``\ *filename*, redirect the write to
the temporary one.
.. option:: -l, --load-snapshot=SNAPSHOT_PARAM
Load an internal snapshot inside *filename* and export it
as an read-only device, SNAPSHOT_PARAM format is
``snapshot.id=[ID],snapshot.name=[NAME]`` or ``[ID_OR_NAME]``
.. option:: --cache=CACHE
qemu-nbd: Change default cache mode to writeback Both qemu and qemu-img use writeback cache mode by default, which is already documented in qemu(1). qemu-nbd uses writethrough cache mode by default, and the default cache mode is not documented. According to the qemu-nbd(8): --cache=CACHE The cache mode to be used with the file. See the documentation of the emulator's -drive cache=... option for allowed values. qemu(1) says: The default mode is cache=writeback. So users have no reason to assume that qemu-nbd is using writethough cache mode. The only hint is the painfully slow writing when using the defaults. Looking in git history, it seems that qemu used writethrough in the past to support broken guests that did not flush data properly, or could not flush due to limitations in qemu. But qemu-nbd clients can use NBD_CMD_FLUSH to flush data, so using writethrough does not help anyone. Change the default cache mode to writback, and document the default and available values properly in the online help and manual. With this change converting image via qemu-nbd is 3.5 times faster. $ qemu-img create dst.img 50g $ qemu-nbd -t -f raw -k /tmp/nbd.sock dst.img Before this change: $ hyperfine -r3 "./qemu-img convert -p -f raw -O raw -T none -W fedora34.img nbd+unix:///?socket=/tmp/nbd.sock" Benchmark #1: ./qemu-img convert -p -f raw -O raw -T none -W fedora34.img nbd+unix:///?socket=/tmp/nbd.sock Time (mean ± σ): 83.639 s ± 5.970 s [User: 2.733 s, System: 6.112 s] Range (min … max): 76.749 s … 87.245 s 3 runs After this change: $ hyperfine -r3 "./qemu-img convert -p -f raw -O raw -T none -W fedora34.img nbd+unix:///?socket=/tmp/nbd.sock" Benchmark #1: ./qemu-img convert -p -f raw -O raw -T none -W fedora34.img nbd+unix:///?socket=/tmp/nbd.sock Time (mean ± σ): 23.522 s ± 0.433 s [User: 2.083 s, System: 5.475 s] Range (min … max): 23.234 s … 24.019 s 3 runs Users can avoid the issue by using --cache=writeback[1] but the defaults should give good performance for the common use case. [1] https://bugzilla.redhat.com/1990656 Signed-off-by: Nir Soffer <nsoffer@redhat.com> Message-Id: <20210813205519.50518-1-nsoffer@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> CC: qemu-stable@nongnu.org Signed-off-by: Eric Blake <eblake@redhat.com>
2021-08-13 22:55:19 +02:00
The cache mode to be used with the file. Valid values are:
``none``, ``writeback`` (the default), ``writethrough``,
``directsync`` and ``unsafe``. See the documentation of
the emulator's ``-drive cache=...`` option for more info.
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
.. option:: -n, --nocache
Equivalent to :option:`--cache=none`.
.. option:: --aio=AIO
qemu-nbd: adds option for aio engines Signed-off-by: Aarushi Mehta <mehta.aaru20@gmail.com> Acked-by: Eric Blake <eblake@redhat.com> Acked-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200120141858.587874-14-stefanha@redhat.com Message-Id: <20200120141858.587874-14-stefanha@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2020-01-20 15:18:56 +01:00
Set the asynchronous I/O mode between ``threads`` (the default),
``native`` (Linux only), and ``io_uring`` (Linux 5.1+).
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
.. option:: --discard=DISCARD
Control whether ``discard`` (also known as ``trim`` or ``unmap``)
requests are ignored or passed to the filesystem. *DISCARD* is one of
``ignore`` (or ``off``), ``unmap`` (or ``on``). The default is
``ignore``.
.. option:: --detect-zeroes=DETECT_ZEROES
Control the automatic conversion of plain zero writes by the OS to
driver-specific optimized zero write commands. *DETECT_ZEROES* is one of
``off``, ``on``, or ``unmap``. ``unmap``
converts a zero write to an unmap operation and can only be used if
*DISCARD* is set to ``unmap``. The default is ``off``.
.. option:: -c, --connect=DEV
Connect *filename* to NBD device *DEV* (Linux only).
.. option:: -d, --disconnect
Disconnect the device *DEV* (Linux only).
.. option:: -e, --shared=NUM
Allow up to *NUM* clients to share the device (default
qemu-nbd: Permit --shared=0 for unlimited clients This gives us better feature parity with QMP nbd-server-start, where max-connections defaults to 0 for unlimited. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20210209152759.209074-3-eblake@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2021-02-09 16:27:59 +01:00
``1``), 0 for unlimited. Safe for readers, but for now,
consistency is not guaranteed between multiple writers.
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
.. option:: -t, --persistent
Don't exit on the last connection.
.. option:: -x, --export-name=NAME
Set the NBD volume export name (default of a zero-length string).
.. option:: -D, --description=DESCRIPTION
Set the NBD volume export description, as a human-readable
string.
.. option:: -L, --list
Connect as a client and list all details about the exports exposed by
a remote NBD server. This enables list mode, and is incompatible
with options that change behavior related to a specific export (such as
:option:`--export-name`, :option:`--offset`, ...).
.. option:: --tls-creds=ID
Enable mandatory TLS encryption for the server by setting the ID
of the TLS credentials object previously created with the --object
option; or provide the credentials needed for connecting as a client
in list mode.
.. option:: --fork
Fork off the server process and exit the parent once the server is running.
.. option:: --pid-file=PATH
Store the server's process ID in the given file.
.. option:: --tls-authz=ID
Specify the ID of a qauthz object previously created with the
:option:`--object` option. This will be used to authorize connecting users
against their x509 distinguished name.
.. option:: -v, --verbose
Display extra debugging information.
.. option:: -h, --help
Display this help and exit.
.. option:: -V, --version
Display version information and exit.
.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
docs: Move qemu-option-trace.rst.inc to docs/ The qemu-option-trace.rst.inc file contains a rST documentation fragment which describes trace options common to qemu-nbd and qemu-img. We put this file into interop/, but we'd like to move the qemu-nbd and qemu-img files into the tools/ manual. We could move the .rst.inc file along with them, but we're eventually going to want to use it for the main QEMU binary options documentation too, and that will be in system/. So move qemu-option-trace.rst.inc to the top-level docs/ directory, where all these files can include it via .. include:: ../qemu-option-trace.rst.inc This does have the slight downside that we now need to explicitly tell Make which manuals use this file rather than relying on a wildcard for all .rst.inc in the manual. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20200217155415.30949-3-peter.maydell@linaro.org
2020-02-25 11:45:13 +01:00
.. include:: ../qemu-option-trace.rst.inc
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
Examples
--------
Start a server listening on port 10809 that exposes only the
guest-visible contents of a qcow2 file, with no TLS encryption, and
with the default export name (an empty string). The command is
one-shot, and will block until the first successful client
disconnects:
::
qemu-nbd -f qcow2 file.qcow2
Start a long-running server listening with encryption on port 10810,
and whitelist clients with a specific X.509 certificate to connect to
a 1 megabyte subset of a raw file, using the export name 'subset':
::
qemu-nbd \
--object tls-creds-x509,id=tls0,endpoint=server,dir=/path/to/qemutls \
--object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,\
O=Example Org,,L=London,,ST=London,,C=GB' \
--tls-creds tls0 --tls-authz auth0 \
-t -x subset -p 10810 \
--image-opts driver=raw,offset=1M,size=1M,file.driver=file,file.filename=file.raw
qemu-nbd: Removed deprecated --partition option The option was deprecated in 4.0.0 (commit 0ae2d546); it's now been long enough with no complaints to follow through with that process. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20200123164650.1741798-3-eblake@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com>
2020-01-23 17:46:50 +01:00
Serve a read-only copy of a guest image over a Unix socket with as
many as 5 simultaneous readers, with a persistent process forked as a
daemon:
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
::
qemu-nbd --fork --persistent --shared=5 --socket=/path/to/sock \
qemu-nbd: Removed deprecated --partition option The option was deprecated in 4.0.0 (commit 0ae2d546); it's now been long enough with no complaints to follow through with that process. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20200123164650.1741798-3-eblake@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com>
2020-01-23 17:46:50 +01:00
--read-only --format=qcow2 file.qcow2
qemu-nbd: Convert invocation documentation to rST The qemu-nbd documentation is currently in qemu-nbd.texi in Texinfo format, which we present to the user as: * a qemu-nbd manpage * a section of the main qemu-doc HTML documentation Convert the documentation to rST format, and present it to the user as: * a qemu-nbd manpage * part of the interop/ Sphinx manual This follows the same pattern as commit 27a296fce982 did for the qemu-ga manpage. All the content of the old manpage is retained, except that I have dropped the "This is free software; see the source for copying conditions. There is NO warranty..." text that was in the old AUTHOR section; Sphinx's manpage builder doesn't expect that much text in the AUTHOR section, and since none of our other manpages have it it seems easiest to delete it rather than try to figure out where else in the manpage to put it. The only other textual change is that I have had to give the --nocache option its own description ("Equivalent to --cache=none") because Sphinx doesn't have an equivalent of using item/itemx to share a description between two options. Some minor aspects of the formatting have changed, to suit what is easiest for Sphinx to output. (The most notable is that Sphinx option section option syntax doesn't support '--option foo=bar' with bar underlined rather than bold, so we have to switch to '--option foo=BAR' instead.) The contents of qemu-option-trace.texi are now duplicated in docs/interop/qemu-option-trace.rst.inc, until such time as we complete the conversion of the other files which use it; since it has had only 3 changes in 3 years, this shouldn't be too awkward a burden. (We use .rst.inc because if this file fragment has a .rst extension then Sphinx complains about not seeing it in a toctree.) Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20200116141511.16849-2-peter.maydell@linaro.org
2020-01-23 16:22:39 +01:00
Expose the guest-visible contents of a qcow2 file via a block device
/dev/nbd0 (and possibly creating /dev/nbd0p1 and friends for
partitions found within), then disconnect the device when done.
Access to bind qemu-nbd to an /dev/nbd device generally requires root
privileges, and may also require the execution of ``modprobe nbd``
to enable the kernel NBD client module. *CAUTION*: Do not use
this method to mount filesystems from an untrusted guest image - a
malicious guest may have prepared the image to attempt to trigger
kernel bugs in partition probing or file system mounting.
::
qemu-nbd -c /dev/nbd0 -f qcow2 file.qcow2
qemu-nbd -d /dev/nbd0
Query a remote server to see details about what export(s) it is
serving on port 10809, and authenticating via PSK:
::
qemu-nbd \
--object tls-creds-psk,id=tls0,dir=/tmp/keys,username=eblake,endpoint=client \
--tls-creds tls0 -L -b remote.example.com
See also
--------
:manpage:`qemu(1)`, :manpage:`qemu-img(1)`
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