The
utility is used for setting up transparent providers on existing ones.
Its main purpose is testing other GEOM classes, as it allows forced provider
removal and I/O error simulation with a given probability.
It also gathers the following statistics: number of read requests, number of
write requests, number of bytes read and number of bytes written.
In addition, it can be used as a good starting point for implementing new GEOM
classes.
The first argument to
indicates an action to be performed:
create
Set up a transparent provider on the given devices.
If the operation succeeds, the new provider should appear with name
/dev/ Ao dev Ac .nop
The kernel module
geom_nop.ko
will be loaded if it is not loaded already.
configure
Configure existing transparent provider.
At the moment it is only used for changing failure probability.
destroy
Turn off the given transparent providers.
reset
Reset statistics for the given transparent providers.
The following
sysctl(8)
variables can be used to control the behavior of the
NOP
GEOM class.
The default value is shown next to each variable.
kern.geom.nop.debug : 0
Debug level of the
NOP
GEOM class.
This can be set to a number between 0 and 2 inclusive.
If set to 0 minimal debug information is printed, and if set to 2 the
maximum amount of debug information is printed.
EXIT STATUS
Exit status is 0 on success, and 1 if the command fails.
EXAMPLES
The following example shows how to create a transparent provider for disk
/dev/da0
with 50% failure probability, and how to destroy it.
gnop create -v -f 50 da0
gnop destroy -v da0.nop
The traffic statistics for the given transparent providers can be obtained
with the
list
command.
The example below shows the number of bytes written with
newfs(8):
