File: stablerestart.5

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.\" Copyright (c) 2009 Rick Macklem, University of Guelph
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd April 10, 2011
.Dt STABLERESTART 5
.Os
.Sh NAME
.Nm nfs-stablerestart
.Nd restart information for the
.Tn NFSv4
server
.Sh SYNOPSIS
.Nm nfs-stablerestart
.Sh DESCRIPTION
The
.Nm
file holds information that allows the
.Tn NFSv4
server to restart without always returning the NFSERR_NOGRACE error, as described in the
.Tn NFSv4
server specification; see
.%T "Network File System (NFS) Version 4 Protocol RFC 3530, Section 8.6.3" .
.Pp
The first record in the file, as defined by struct nfsf_rec in
/usr/include/fs/nfs/nfsrvstate.h, holds the lease duration of the
last incarnation of the server and the number of boot times that follows.
Following this are the number of previous boot times listed in the
first record.
The lease duration is used to set the grace period.
The boot times
are used to avoid the unlikely occurrence of a boot time being reused,
due to a TOD clock going backwards. This record and the previous boot times with this boot time added is re-written at the
end of the grace period.
.Pp
The rest of the file are appended records, as defined by
struct nfst_rec in /usr/include/fs/nfs/nfsrvstate.h and are used
represent one of two things. There are records which indicate that a
client successfully acquired state and records that indicate a client's state was revoked.
State revoke records indicate that state information
for a client was discarded, due to lease expiry and an otherwise
conflicting open or lock request being made by a different client.
These records can be used
to determine if clients might have done either of the
edge conditions.
.Pp
If a client might have done either edge condition or this file is
empty or corrupted, the server returns NFSERR_NOGRACE for any reclaim
request from the client.
.Pp
For correct operation of the server, it must be ensured that the file
is written to stable storage by the time a write op with IO_SYNC specified
has returned. This might require hardware level caching to be disabled for
a local disk drive that holds the file, or similar.
.Sh FILES
.Bl -tag -width /var/lib/freebsd-nfs-server/nfs-stablerestart.bak -compact
.It Pa /var/lib/freebsd-nfs-server/nfs-stablerestart
NFSv4 stable restart file
.It Pa /var/lib/freebsd-nfs-server/nfs-stablerestart.bak
backup copy of the file
.El
.Sh SEE ALSO
.Xr nfsv4 4 ,
.Xr nfsd 8
.Sh BUGS
If the file is empty, the NFSv4 server has no choice but to return
NFSERR_NOGRACE for all reclaim requests. Although correct, this is
a highly undesirable occurrence, so the file should not be lost if
at all possible. The backup copy of the file is maintained
and used by the
.Xr nfsd 8
to minimize the risk of this occurring.
To move the file, you must edit
the nfsd sources and recompile it. This was done to discourage
accidental relocation of the file.