freebsd-nq/sbin/geom/class/nop/gnop.8

.\" Copyright (c) 2004-2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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.Dd May 21, 2004
.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 f Ar failprob
.Op Fl o Ar offset
.Op Fl s Ar size
.Op Fl S Ar secsize
.Ar dev ...
.Nm
.Cm configure
.Op Fl v
.Op Fl f Ar failprob
.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 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 implementing new GEOM
class.
.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 f Ar failprob"
.It Fl f
Force the removal of the specified provider.
.It Fl f Ar failprob
Specifies failure probability in percentage.
.It Fl o Ar offset
Where to begin on the original provider.
.It Fl s Ar size
Size of the transparent provider.
.It Fl S Ar secsize
Sector size of the transparent provider.
.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, and if set to 2 the
maximum amount of debug information is printed.
.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% failure probability, and how to destroy it.
.Bd -literal -offset indent
gnop create -v -f 50 da0
gnop destroy -v da0.nop
.Ed
.Pp
The traffic statistics for the given transparent providers we can get with
.Cm list
command.
Example below shows how can we obtain 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