DragonFly On-Line Manual Pages

QEMU-PR-HELPER(8)                    QEMU                    QEMU-PR-HELPER(8)

NAME
       qemu-pr-helper - QEMU persistent reservation helper

SYNOPSIS
       qemu-pr-helper [OPTION]

DESCRIPTION
       Implements the persistent reservation helper for QEMU.

       SCSI persistent reservations allow restricting access to block devices
       to specific initiators in a shared storage setup.  When implementing
       clustering of virtual machines, it is a common requirement for virtual
       machines to send persistent reservation SCSI commands.  However, the
       operating system restricts sending these commands to unprivileged
       programs because incorrect usage can disrupt regular operation of the
       storage fabric. QEMU's SCSI passthrough devices scsi-block and
       scsi-generic support passing guest persistent reservation requests to a
       privileged external helper program. qemu-pr-helper is that external
       helper; it creates a listener socket which will accept incoming
       connections for communication with QEMU.

       If you want to run VMs in a setup like this, this helper should be
       started as a system service, and you should read the QEMU manual
       section on "persistent reservation managers" to find out how to
       configure QEMU to connect to the socket created by qemu-pr-helper.

       After connecting to the socket, qemu-pr-helper can optionally drop root
       privileges, except for those capabilities that are needed for its
       operation.

       qemu-pr-helper can also use the systemd socket activation protocol.  In
       this case, the systemd socket unit should specify a Unix stream socket,
       like this:

          [Socket]
          ListenStream=/var/run/qemu-pr-helper.sock

OPTIONS

       -d, --daemon
              run in the background (and create a PID file)

       -q, --quiet
              decrease verbosity

       -v, --verbose
              increase verbosity

       -f, --pidfile=PATH
              PID file when running as a daemon. By default the PID file is
              created in the system runtime state directory, for example
              /var/run/qemu-pr-helper.pid.

       -k, --socket=PATH
              path to the socket. By default the socket is created in the
              system runtime state directory, for example
              /var/run/qemu-pr-helper.sock.

       -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
              Specify tracing options.

              [enable=]PATTERN
                 Immediately enable events matching PATTERN (either event name
                 or a globbing pattern).  This option is only available if
                 QEMU has been compiled with the simple, log or ftrace tracing
                 backend.  To specify multiple events or patterns, specify the
                 -trace option multiple times.

                 Use -trace help to print a list of names of trace points.

              events=FILE
                 Immediately enable events listed in FILE.  The file must
                 contain one event name (as listed in the trace-events-all
                 file) per line; globbing patterns are accepted too.  This
                 option is only available if QEMU has been compiled with the
                 simple, log or ftrace tracing backend.

              file=FILE
                 Log output traces to FILE.  This option is only available if
                 QEMU has been compiled with the simple tracing backend.

       -u, --user=USER
              user to drop privileges to

       -g, --group=GROUP
              group to drop privileges to

       -h, --help
              Display a help message and exit.

       -V, --version
              Display version information and exit.

COPYRIGHT
       2022, The QEMU Project Developers

8.0.2                           October 1, 2023              QEMU-PR-HELPER(8)