qemu

FORK: QEMU emulator
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qemu-pr-helper.rst (2602B)

      1 ==================================
      2 QEMU persistent reservation helper
      3 ==================================
      4 
      5 Synopsis
      6 --------
      7 
      8 **qemu-pr-helper** [*OPTION*]
      9 
     10 Description
     11 -----------
     12 
     13 Implements the persistent reservation helper for QEMU.
     14 
     15 SCSI persistent reservations allow restricting access to block devices
     16 to specific initiators in a shared storage setup.  When implementing
     17 clustering of virtual machines, it is a common requirement for virtual
     18 machines to send persistent reservation SCSI commands.  However,
     19 the operating system restricts sending these commands to unprivileged
     20 programs because incorrect usage can disrupt regular operation of the
     21 storage fabric. QEMU's SCSI passthrough devices ``scsi-block``
     22 and ``scsi-generic`` support passing guest persistent reservation
     23 requests to a privileged external helper program. :program:`qemu-pr-helper`
     24 is that external helper; it creates a listener socket which will
     25 accept incoming connections for communication with QEMU.
     26 
     27 If you want to run VMs in a setup like this, this helper should be
     28 started as a system service, and you should read the QEMU manual
     29 section on "persistent reservation managers" to find out how to
     30 configure QEMU to connect to the socket created by
     31 :program:`qemu-pr-helper`.
     32 
     33 After connecting to the socket, :program:`qemu-pr-helper` can
     34 optionally drop root privileges, except for those capabilities that
     35 are needed for its operation.
     36 
     37 :program:`qemu-pr-helper` can also use the systemd socket activation
     38 protocol.  In this case, the systemd socket unit should specify a
     39 Unix stream socket, like this::
     40 
     41     [Socket]
     42     ListenStream=/var/run/qemu-pr-helper.sock
     43 
     44 Options
     45 -------
     46 
     47 .. program:: qemu-pr-helper
     48 
     49 .. option:: -d, --daemon
     50 
     51   run in the background (and create a PID file)
     52 
     53 .. option:: -q, --quiet
     54 
     55   decrease verbosity
     56 
     57 .. option:: -v, --verbose
     58 
     59   increase verbosity
     60 
     61 .. option:: -f, --pidfile=PATH
     62 
     63   PID file when running as a daemon. By default the PID file
     64   is created in the system runtime state directory, for example
     65   :file:`/var/run/qemu-pr-helper.pid`.
     66 
     67 .. option:: -k, --socket=PATH
     68 
     69   path to the socket. By default the socket is created in
     70   the system runtime state directory, for example
     71   :file:`/var/run/qemu-pr-helper.sock`.
     72 
     73 .. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
     74 
     75   .. include:: ../qemu-option-trace.rst.inc
     76 
     77 .. option:: -u, --user=USER
     78 
     79   user to drop privileges to
     80 
     81 .. option:: -g, --group=GROUP
     82 
     83   group to drop privileges to
     84 
     85 .. option:: -h, --help
     86 
     87   Display a help message and exit.
     88 
     89 .. option:: -V, --version
     90 
     91   Display version information and exit.