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 pro-
grams 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 connec-
tions 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 sec-
tion 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 oper-
ation.
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 sys-
tem 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 con-
tain 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
7.2.11 May 09, 2024 QEMU-PR-HELPER(8)
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