gnop(8)

NAME

gnop - control utility for NOP GEOM class

SYNOPSIS

gnop create [-v] [-f failprob] [-o  offset]  [-s  size]  [-S
secsize] dev ...
gnop configure [-v] [-f failprob] prov ...
gnop destroy [-fv] prov ...
gnop reset [-v] prov ...
gnop list
gnop status
gnop load
gnop unload

DESCRIPTION

The gnop 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 giv

en probability. It also gathers the following statistics: number of

read requests,
number of write requests, number of read bytes and number of

wrote bytes.
In addition, it can be used as a good starting point for im

plementing new
GEOM class.

The first argument to gnop indicates an action to be per

formed:

create Set up a transparent provider on the given

devices. If

the operation succeeds, the new provider

should appear
with name /dev/<dev>.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 probabili

ty.

destroy Turn off the given transparent providers.

reset Reset statistics for the given transparent

providers.

list See geom(8).

status See geom(8).

load See geom(8).

unload See geom(8).

Additional options:

-f Force the removal of the specified

provider.

-f failprob Specifies failure probability in percent

age.

-o offset Where to begin on the original provider.

-s size Size of the transparent provider.

-S secsize Sector size of the transparent provider.

-v Be more verbose.

SYSCTL VARIABLES

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 de

bug 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

we can get
with list command. Example below shows how can we obtain

number of bytes
written with newfs(8):

gnop create da0
newfs /dev/da0.nop
gnop list

SEE ALSO

geom(4), geom(8)

HISTORY

The gnop utility appeared in FreeBSD 5.3.

AUTHORS

Pawel Jakub Dawidek <pjd@FreeBSD.org>

BSD May 21, 2004

BSD