.\" Copyright (c) 2004-2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd October 10, 2015
.Dt GNOP 8
.Os
.Sh NAME
.Nm gnop
.Nd "control utility for NOP GEOM class"
.Sh SYNOPSIS
.Nm
.Cm create
.Op Fl v
.Op Fl e Ar error
.Op Fl o Ar offset
.Op Fl p Ar stripesize
.Op Fl P Ar stripeoffset
.Op Fl r Ar rfailprob
.Op Fl s Ar size
.Op Fl S Ar secsize
.Op Fl w Ar wfailprob
.Ar dev ...
.Nm
.Cm configure
.Op Fl v
.Op Fl e Ar error
.Op Fl r Ar rfailprob
.Op Fl w Ar wfailprob
.Ar prov ...
.Nm
.Cm destroy
.Op Fl fv
.Ar prov ...
.Nm
.Cm reset
.Op Fl v
.Ar prov ...
.Nm
.Cm list
.Nm
.Cm status
.Nm
.Cm load
.Nm
.Cm unload
.Sh DESCRIPTION
The
.Nm
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 statistics on the number of read, write, delete,
getattr, flush, and other requests, and the number of bytes read and written.
.Nm
can also be used as a good starting point for implementing new GEOM
classes.
.Pp
The first argument to
.Nm
indicates an action to be performed:
.Bl -tag -width ".Cm configure"
.It Cm create
Set up a transparent provider on the given devices.
If the operation succeeds, the new provider should appear with name
.Pa /dev/ Ns Ao Ar dev Ac Ns Pa .nop .
The kernel module
.Pa geom_nop.ko
will be loaded if it is not loaded already.
.It Cm configure
Configure existing transparent provider.
At the moment it is only used for changing failure probability.
.It Cm destroy
Turn off the given transparent providers.
.It Cm reset
Reset statistics for the given transparent providers.
.It Cm list
See
.Xr geom 8 .
.It Cm status
See
.Xr geom 8 .
.It Cm load
See
.Xr geom 8 .
.It Cm unload
See
.Xr geom 8 .
.El
.Pp
Additional options:
.Bl -tag -width ".Fl r Ar rfailprob"
.It Fl e Ar error
Specifies the error number to return on failure.
.It Fl f
Force the removal of the specified provider.
.It Fl o Ar offset
Where to begin on the original provider.
.It Fl p Ar stripesize
Value of the stripesize property of the transparent provider.
.It Fl P Ar stripeoffset
Value of the stripeoffset property of the transparent provider.
.It Fl r Ar rfailprob
Specifies read failure probability in percent.
.It Fl s Ar size
Size of the transparent provider.
.It Fl S Ar secsize
Sector size of the transparent provider.
.It Fl w Ar wfailprob
Specifies write failure probability in percent.
.It Fl v
Be more verbose.
.El
.Sh SYSCTL VARIABLES
The following
.Xr sysctl 8
variables can be used to control the behavior of the
.Nm NOP
GEOM class.
The default value is shown next to each variable.
.Bl -tag -width indent
.It Va kern.geom.nop.debug : No 0
Debug level of the
.Nm 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.
.El
.Sh EXIT STATUS
Exit status is 0 on success, and 1 if the command fails.
.Sh EXAMPLES
The following example shows how to create a transparent provider for disk
.Pa /dev/da0
with 50% write failure probability, and how to destroy it.
.Bd -literal -offset indent
gnop create -v -w 50 da0
gnop destroy -v da0.nop
.Ed
.Pp
The traffic statistics for the given transparent providers can be obtained
with the
.Cm list
command.
The example below shows the number of bytes written with
.Xr newfs 8 :
.Bd -literal -offset indent
gnop create da0
newfs /dev/da0.nop
gnop list
.Ed
.Sh SEE ALSO
.Xr geom 4 ,
.Xr geom 8
.Sh HISTORY
The
.Nm
utility appeared in
.Fx 5.3 .
.Sh AUTHORS
.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org