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lockd(1M)							     lockd(1M)

NAME    [Toc]    [Back]

     lockd - NFS lock daemon

SYNOPSIS    [Toc]    [Back]

     /usr/etc/rpc.lockd	[ -g graceperiod ] [ -l	] [ nservers ]

DESCRIPTION    [Toc]    [Back]

     lockd provides the	inherently stateful locking services within the
     stateless NFS environment.	 It allows the locking of records and files
     between applications running on different physical	machines sharing the
     same filesystems mounted with NFS.	 nservers is the number	of lockd
     servers to	start.

     Locks are presently advisory only.	 The lock style	implemented by lockd
     is	that specified in the SVID (see	lockf(3C) and fcntl(2)).  There	is no
     interaction between the lockd's locks and flock(3B) style locks.

     lockd is started during system initialization if the chkconfig(1M)	lockd
     flag is set on.  Command-line options belong in

     If	nfsd(1M) is running, lockd registers its RPC services and exits,
     leaving nfsd to handle the	requests.

     lockd processes lock requests that	are either sent	locally	by the kernel
     or	remotely by another lock daemon.  In the case of local lock requests
     for remote	data, lockd forwards the lock requests to the server site's
     lock daemon through the RPC/XDR(3R) package.  lockd then requests the
     local status monitor daemon, statd(1M), for monitor service of the
     server.  The reply	to the lock request is not sent	to the kernel until
     the status	daemon and the server site's lock daemon have replied.

     When a server recovers, it	waits for a grace period for all client	site
     lockds to submit reclaim requests.	 Client	site lockds are	notified by
     the statd of the server recovery and promptly resubmit previously granted
     lock requests.  If	a lockd	fails to secure	a previously granted lock at
     the server	site, it sends SIGUSR1 to the application process.  The
     process must explicitly handle this signal	if the loss of a lock should
     cause it to terminate.

OPTIONS    [Toc]    [Back]

     -g	graceperiod   lockd uses graceperiod (seconds) as the grace period
		      duration instead of the default value (see TUNING

     -l		      Set SVID locks for files which are locked	by DOS
		      machines running PC-NFS and compatible file sharing
		      utilities.  Normally, lockd does not set SVID locks for
		      such requests.

									Page 1

lockd(1M)							     lockd(1M)

TUNING    [Toc]    [Back]

     lockd has four tunable parameters:	 lockd_grace_period,
     lock_share_requests, nlm_granted_timeout, and nlm_maxdupreqs.
     lockd_grace_period	controls the starup grace period for the reclaiming of
     locks.  This was previously controlled by the -g command line option.
     Lock_share_requests tells lockd to	preform	UNIX file locking for share
     and unshare requests.  Nlm_granted_timeout	controls the timeout used in
     making NLM_GRANTED	and NLMPROC_GRANTED callbacks for blocked lock
     requests which have been granted.	This value is specified	in tenths of a
     second.  Nlm_maxdupreqs controls how many NLM RPC duplicate request cache
     entries are allocated.  The default setting is 0.	This causes the
     allocation	to be sized based upon the memory size of the system.

NOTES    [Toc]    [Back]

     The reply to a lock request for remote data is delayed until all daemons
     become available.

     In	the Sun	implementation,	lockd sends SIGLOST.  when a lock is lost.
     The IRIX implementation sends SIGUSR1.  Programs should establish a
     signal handler to catch this signal and exit.

     For client	operations, lockd is no	longer used as the intermediary	for
     NLM RPCs.	The kernel makes the RPCs to the server	directly.  These calls
     all use UDP.  There is no support for TCP as a transport for NLM RPCs on
     the client	side.

     Since NLM RPCs are	handled	by the NFS server nfsd,	both TCP and UDP are
     accepted as transports on the server side.	 For blocked lock requests,
     however, the NLM_GRANTED or NLM_GRANTED_MSG RPC will be sent using	UDP
     regardless	of what	transport the client used.

SEE ALSO    [Toc]    [Back]

     statd(1M),	fcntl(2), signal(2), lockf(3C).

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