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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 2023, The QEMU Project Developers 8.2.10 Apr 12, 2025 QEMU-PR-HELPER(8)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | COPYRIGHT
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