GNOP(8)                 FreeBSD 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 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.  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:

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

     -d delaymsec         Specifies the delay of the requests in milliseconds.
                          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 transparent
                          provider.

     -P stripeoffset      Value of the stripeoffset property of the
                          transparent 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 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
             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.

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>

FreeBSD 13.1-RELEASE-p6        December 29, 2019       FreeBSD 13.1-RELEASE-p6