GNOP(8)

NAME
gnop - control utility for NOP GEOM class

SYNOPSIS
gnop create [-v] [-e error] [-o offset] [-r rfailprob] [-s size] [-S secsize] [-w wfailprob] dev ...
gnop configure [-v] [-e error] [-r rfailprob] [-w wfailprob] 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 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 gnop 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/<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 probability.

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:

-e error
    Specifies the error number to return on failure.

-f  Force the removal of the specified provider.

-o offset
    Where to begin on the original provider.

-r rfailprob
    Specifies read failure probability in percent.

-s size
    Size of the transparent provider.

-S secsize
    Sector size of the transparent provider.

-w wfailprob
    Specifies write failure probability in percent.

-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 debug information is printed. If set to 1, basic debug information is logged along with the I/O requests that were returned as errors. If set to 2, the maximum amount of debug information is printed including all I/O requests.

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% write failure probability, and how to destroy it.

    gnop create -v -w 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):

    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>