GNOP(8) BSD System Manager's Manual GNOP(8)NAMEgnop — control utility for NOP GEOM class
SYNOPSISgnop 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 ...
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 the following statistics: number of read requests,
number of write requests, number of bytes read and number of bytes writ‐
ten. In addition, it can 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).
-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.
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.
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, and if set to 2 the maximum amount of debug informa‐
tion is printed.
Exit status is 0 on success, and 1 if the command fails.
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
SEE ALSOgeom(4), geom(8)HISTORY
The gnop utility appeared in FreeBSD 5.3.
Pawel Jakub Dawidek ⟨pjd@FreeBSD.org⟩
BSD September 17, 2009 BSD