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 socket which QEMU can connect to  to  communicate  with
       it.

       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

       2024, The QEMU Project Developers