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

NAME
       gnop -- control utility for NOP GEOM class

SYNOPSIS
       gnop  create  [-v]  [-c	count_until_fail]  [-d	delaymsec]  [-e	error]
	    [-o	offset]	[-p  stripesize]  [-P  stripeoffset]  [-q  rdelayprob]
	    [-r	  rfailprob]   [-s   size]   [-S   secsize]   [-w   wfailprob]
	    [-x	wdelayprob] [-z	physpath] [-Z gnopname]	dev ...
       gnop configure [-v] [-c count_until_fail]  [-d  delaymsec]  [-e	error]
	    [-q	rdelayprob] [-r	rfailprob] [-w wfailprob] [-x wdelayprob] 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	exist-
       ing 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 implement-
       ing 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:

       -c count_until_fail  Specifies the number of I/O	requests to allow  be-
			    fore  setting  the	read,  write and delay failure
			    probabilities.

       -d delaymsec	    Specifies the delay	of the requests	 in  millisec-
			    onds.   Note  that requests	will be	delayed	before
			    they are sent to the backing device.

       -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  transpar-
			    ent	provider.

       -P stripeoffset	    Value  of  the stripeoffset	property of the	trans-
			    parent provider.

       -q rdelayprob	    Specifies read delay probability in	percent.

       -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.

       -x wdelayprob	    Specifies write delay probability in percent.

       -z physpath	    Physical path of the transparent provider.

       -Z gnopname	    The	name of	the new	provider.  The	suffix	".nop"
			    will be appended to	the provider name.

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	 vari-
       able.

       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  er-
	       rors.   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  ob-
       tained  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>

FreeBSD	13.2		       December	29, 2019		       GNOP(8)

NAME | SYNOPSIS | DESCRIPTION | SYSCTL VARIABLES | EXIT STATUS | EXAMPLES | SEE ALSO | HISTORY | AUTHORS

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