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98 lines
4.0 KiB
Groff
98 lines
4.0 KiB
Groff
.\" Copyright (c) 2009 Rick Macklem, University of Guelph
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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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.\"
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.Dd April 10, 2011
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.Dt STABLERESTART 5
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.Os
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.Sh NAME
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.Nm nfs-stablerestart
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.Nd restart information for the
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.Tn NFSv4
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server
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.Sh SYNOPSIS
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.Nm nfs-stablerestart
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.Sh DESCRIPTION
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The
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.Nm
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file holds information that allows the
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.Tn NFSv4
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server to restart without always returning the NFSERR_NOGRACE error, as described in the
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.Tn NFSv4
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server specification; see
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.%T "Network File System (NFS) Version 4 Protocol RFC 3530, Section 8.6.3" .
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.Pp
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The first record in the file, as defined by struct nfsf_rec in
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/usr/include/fs/nfs/nfsrvstate.h, holds the lease duration of the
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last incarnation of the server and the number of boot times that follows.
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Following this are the number of previous boot times listed in the
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first record.
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The lease duration is used to set the grace period.
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The boot times
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are used to avoid the unlikely occurrence of a boot time being reused,
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due to a TOD clock going backwards. This record and the previous boot times with this boot time added is re-written at the
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end of the grace period.
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.Pp
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The rest of the file are appended records, as defined by
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struct nfst_rec in /usr/include/fs/nfs/nfsrvstate.h and are used
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represent one of two things. There are records which indicate that a
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client successfully acquired state and records that indicate a client's state was revoked.
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State revoke records indicate that state information
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for a client was discarded, due to lease expiry and an otherwise
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conflicting open or lock request being made by a different client.
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These records can be used
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to determine if clients might have done either of the
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edge conditions.
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.Pp
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If a client might have done either edge condition or this file is
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empty or corrupted, the server returns NFSERR_NOGRACE for any reclaim
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request from the client.
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.Pp
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For correct operation of the server, it must be ensured that the file
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is written to stable storage by the time a write op with IO_SYNC specified
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has returned. This might require hardware level caching to be disabled for
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a local disk drive that holds the file, or similar.
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.Sh FILES
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.Bl -tag -width /var/db/nfs-stablerestart.bak -compact
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.It Pa /var/db/nfs-stablerestart
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NFSv4 stable restart file
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.It Pa /var/db/nfs-stablerestart.bak
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backup copy of the file
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.El
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.Sh SEE ALSO
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.Xr nfsv4 4 ,
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.Xr nfsd 8
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.Sh BUGS
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If the file is empty, the NFSv4 server has no choice but to return
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NFSERR_NOGRACE for all reclaim requests. Although correct, this is
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a highly undesirable occurrence, so the file should not be lost if
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at all possible. The backup copy of the file is maintained
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and used by the
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.Xr nfsd 8
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to minimize the risk of this occurring.
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To move the file, you must edit
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the nfsd sources and recompile it. This was done to discourage
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accidental relocation of the file.
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