190 lines
6.0 KiB
Groff
190 lines
6.0 KiB
Groff
.\" Copyright (c) 2013 Edward Tomasz Napierala
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.\" Copyright (c) 2015 Alexander Motin <mav@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.Dd September 12, 2015
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.Dt CTL 4
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.Os
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.Sh NAME
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.Nm ctl
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.Nd CAM Target Layer / iSCSI target
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device iscsi"
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.Cd "device ctl"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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ctl_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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subsystem provides SCSI disk and processor emulation.
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It supports features such as:
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.Pp
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.Bl -bullet -compact
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.It
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Disk and processor device emulation
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.It
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Tagged queueing
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.It
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SCSI task attribute support (ordered, head of queue, simple tags)
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.It
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SCSI implicit command ordering support
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.It
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Full task management support (abort, LUN reset, target reset, etc.)
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.It
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Support for multiple ports
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.It
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Support for multiple simultaneous initiators
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.It
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Support for multiple simultaneous backing stores
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.It
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Support for VMWare VAAI: COMPARE AND WRITE, XCOPY, WRITE SAME,
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and UNMAP commands
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.It
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Support for Microsoft ODX: POPULATE TOKEN/WRITE USING TOKEN,
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WRITE SAME, and UNMAP commands
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.It
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Persistent reservation support
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.It
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Mode sense/select support
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.It
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Error injection support
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.It
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High Availability clustering support with ALUA
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.It
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All I/O handled in-kernel, no userland context switch overhead
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.El
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.Pp
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It also serves as a kernel component of the native iSCSI target.
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.Sh SYSCTL VARIABLES
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The following variables are available as both
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.Xr sysctl 8
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variables and
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.Xr loader 8
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tunables:
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.Bl -tag -width indent
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.It Va kern.cam.ctl.debug
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Bit mask of enabled CTL log levels:
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.Bl -tag -offset indent -compact
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.It 1
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log commands with errors;
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.It 2
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log all commands;
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.It 4
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log data for commands other then READ/WRITE.
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.El
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Defaults to 0.
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.It Va kern.cam.ctl.ha_id
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Specifies unique position of this node within High Availability cluster.
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Default is 0 -- no HA, 1 and 2 -- HA enabled at specified position.
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.It Va kern.cam.ctl.ha_mode
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Specifies High Availability cluster operation mode:
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.Bl -tag -offset indent -compact
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.It 0
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Active/Standby -- primary node has backend access and processes requests,
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while secondary can only do basic LUN discovery and reservation;
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.It 1
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Active/Active -- both nodes have backend access and process requests,
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while secondary node synchronizes processing with primary one;
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.It 2
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Active/Active -- primary node has backend access and processes requests,
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while secondary node forwards all requests and data to primary one;
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.El
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All above modes require established connection between HA cluster nodes.
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If connection is not configured, secondary node will report Unavailable
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state; if configured but not established -- Transitioning state.
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Defaults to 0.
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.It Va kern.cam.ctl.ha_peer
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String value, specifying method to establish connection to peer HA node.
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Can be "listen IP:port", "connect IP:port" or empty.
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.It Va kern.cam.ctl.ha_link
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Reports present state of connection between HA cluster nodes:
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.Bl -tag -offset indent -compact
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.It 0
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not configured;
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.It 1
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configured but not established;
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.It 2
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established.
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.El
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.It Va kern.cam.ctl.ha_role
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Specifies default role of this node:
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.Bl -tag -offset indent -compact
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.It 0
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primary;
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.It 1
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secondary.
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.El
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This role can be overriden on per-LUN basis using "ha_role" LUN option,
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so that for one LUN one node is primary, while for another -- another.
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Role change from primary to secondary for HA modes 0 and 2 closes backends,
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the opposite change -- opens.
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If there is no primary node (both nodes are secondary, or secondary node has
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no connection to primary one), secondary node(s) report Transitioning state.
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State with two primary nodes is illegal (split brain condition).
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.It Va kern.cam.ctl.iscsi.debug
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Verbosity level for log messages from the kernel part of iSCSI target.
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Set to 0 to disable logging or 1 to warn about potential problems.
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Larger values enable debugging output.
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Defaults to 1.
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.It Va kern.cam.ctl.iscsi.maxcmdsn_delta
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The number of outstanding commands to advertise to the iSCSI initiator.
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Technically, it is the difference between ExpCmdSN and MaxCmdSN fields
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in the iSCSI PDU.
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Defaults to 256.
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.It Va kern.cam.ctl.iscsi.ping_timeout
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The number of seconds to wait for the iSCSI initiator to respond to a NOP-In
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PDU.
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In the event that there is no response within that time the session gets
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forcibly terminated.
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Set to 0 to disable sending NOP-In PDUs.
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Defaults to 5.
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.El
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.Sh SEE ALSO
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.Xr ctladm 8 ,
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.Xr ctld 8 ,
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.Xr ctlstat 8
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.Sh HISTORY
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The
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.Nm
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subsystem first appeared in
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.Fx 9.1 .
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.Sh AUTHORS
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The
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.Nm
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subsystem was originally written by
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.An Kenneth Merry Aq Mt ken@FreeBSD.org .
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Later work was done by
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.An Alexander Motin Aq Mt mav@FreeBSD.org .
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