vmt(4)
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VMT(4) NetBSD/x86 Kernel Interfaces Manual VMT(4)
NAME
vmt -- VMware Tools driver
SYNOPSIS
vmt0 at cpu0
DESCRIPTION
The vmt driver is a kernel level implementation of VMware Tools. VMware
Tools are intended to provide better support for operating systems run-
ning inside virtual machines.
vmt handles shutdown, reboot, resume requests from the host by sending
events using sysmon_pswitch(9) of type PSWITCH_TYPE_POWER,
PSWITCH_TYPE_RESET, and PSWITCH_TYPE_SLEEP that can be handled by
powerd(8). vmt will log notifications that the guest has been suspended
or resumed by the host.
vmt reports the guest's hostname and first non-loopback IP address to the
host.
Clock synchronization
The vmt driver synchronizes the virtual machine's clock with the host
clock in the following situations:
· When the virtual machine resumes after having been suspended.
· Periodically with the interval indicated by the
machdep.vmt0.clock_sync.period sysctl(8) variable. This is done so
that the virtual machine can keep its clock synchronized when the
host is suspended, because in this case the vmt driver receives no
notification of such an event. Setting this tunable to zero disables
clock synchronization.
SEE ALSO
powerd(8)
HISTORY
The vmt driver first appeared in OpenBSD 4.4 and was then ported to
NetBSD 6.0.
AUTHORS
The vmt driver was written by David Gwynne <dlg@openbsd.org>.
BUGS
vmt is known to cause a conflict with vmtoolsd(8) from open-vm-tools.
vmt works by establishing an RPC channel called TCLO between VMware guest
and host to receive controlling messages from the host. The problem is
that vmt is essentially a subset of vmtoolsd(8), and they both use the
same RPC channel, but TCLO is never meant to be simultaneously used by
two distinct services in the same VM guest. So when vmtoolsd(8) is run-
ning while also vmt is active, they continually fight for the channel,
both get rejected by the confused VM host, and neither one can establish
a stable communication line.
So before launching vmtoolsd(8) the vmt driver should be detached by run-
ning:
# drvctl -d vmt0
And after terminating vmtoolsd(8) the vmt driver should be re-attached by
running:
# drvctl -r -a cpufeaturebus cpu0
NetBSD 10.99 October 6, 2013 NetBSD 10.99
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