GNOP(8) 		  BSD System Manager's Manual		       GNOP(8)

NAME
     gnop — control utility for NOP GEOM class

SYNOPSIS
     gnop create [-v] [-e error] [-o offset] [-p stripesize] [-P stripeoffset]
	  [-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 probabil‐
     ity.  It also gathers statistics on the number of read, write, delete,
     getattr, flush, and other requests, and the number of bytes read and
     written.  gnop can also 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.

     -p stripesize
		   Value of the stripesize property of the transparent
		   provider.

     -P stripeoffset
		   Value of the stripeoffset property of the transparent
		   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 informa‐
	     tion 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 includ‐
	     ing 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⟩

BSD			       October 10, 2015 			   BSD