QEMU persistent reservation helper¶
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-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:
- -d, --daemon¶
run in the background (and create a PID file)
- -q, --quiet¶
- -v, --verbose¶
- -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
- -k, --socket=PATH¶
path to the socket. By default the socket is created in the system runtime state directory, for example
- -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]¶
Specify tracing options.
Immediately enable events matching PATTERN (either event name or a globbing pattern). This option is only available if QEMU has been compiled with the
ftracetracing backend. To specify multiple events or patterns, specify the
-traceoption multiple times.
-trace helpto print a list of names of trace points.
Immediately enable events listed in FILE. The file must contain one event name (as listed in the
trace-events-allfile) per line; globbing patterns are accepted too. This option is only available if QEMU has been compiled with the
Log output traces to FILE. This option is only available if QEMU has been compiled with the
- -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.