2021-09-07 15:58:12 +02:00
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==================================
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2020-11-12 14:40:40 +00:00
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QEMU persistent reservation helper
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==================================
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Synopsis
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--------
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**qemu-pr-helper** [*OPTION*]
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Description
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-----------
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Implements the persistent reservation helper for QEMU.
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SCSI persistent reservations allow restricting access to block devices
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to specific initiators in a shared storage setup. When implementing
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clustering of virtual machines, it is a common requirement for virtual
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machines to send persistent reservation SCSI commands. However,
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the operating system restricts sending these commands to unprivileged
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programs because incorrect usage can disrupt regular operation of the
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storage fabric. QEMU's SCSI passthrough devices ``scsi-block``
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and ``scsi-generic`` support passing guest persistent reservation
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requests to a privileged external helper program. :program:`qemu-pr-helper`
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2022-07-07 17:37:15 +01:00
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is that external helper; it creates a listener socket which will
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accept incoming connections for communication with QEMU.
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2020-11-12 14:40:40 +00:00
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If you want to run VMs in a setup like this, this helper should be
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started as a system service, and you should read the QEMU manual
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section on "persistent reservation managers" to find out how to
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configure QEMU to connect to the socket created by
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:program:`qemu-pr-helper`.
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After connecting to the socket, :program:`qemu-pr-helper` can
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optionally drop root privileges, except for those capabilities that
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are needed for its operation.
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:program:`qemu-pr-helper` can also use the systemd socket activation
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protocol. In this case, the systemd socket unit should specify a
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Unix stream socket, like this::
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[Socket]
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ListenStream=/var/run/qemu-pr-helper.sock
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Options
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-------
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.. program:: qemu-pr-helper
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.. option:: -d, --daemon
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run in the background (and create a PID file)
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.. option:: -q, --quiet
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decrease verbosity
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.. option:: -v, --verbose
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increase verbosity
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.. option:: -f, --pidfile=PATH
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PID file when running as a daemon. By default the PID file
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is created in the system runtime state directory, for example
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:file:`/var/run/qemu-pr-helper.pid`.
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.. option:: -k, --socket=PATH
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path to the socket. By default the socket is created in
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the system runtime state directory, for example
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:file:`/var/run/qemu-pr-helper.sock`.
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.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
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.. include:: ../qemu-option-trace.rst.inc
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.. option:: -u, --user=USER
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user to drop privileges to
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.. option:: -g, --group=GROUP
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group to drop privileges to
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.. option:: -h, --help
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Display a help message and exit.
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.. option:: -V, --version
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Display version information and exit.
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