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SYNCER(4)	       FreeBSD Kernel Interfaces Manual		     SYNCER(4)

NAME
     syncer -- file system synchronizer	kernel process

SYNOPSIS
     syncer

DESCRIPTION
     The syncer	kernel process helps protect the integrity of disk volumes by
     flushing volatile cached file system data to disk.

     The kernel	places all vnode(9)'s in a number of queues.  The syncer
     process works through the queues in a round-robin fashion,	usually	pro-
     cessing one queue per second.  For	each vnode(9) on that queue, the
     syncer process forces a write out to disk of its dirty buffers.

     The usual delay between the time buffers are dirtied and the time they
     are synced	is controlled by the following sysctl(8) tunable variables:

     Variable	      Default	   Description
     kern.filedelay   30	   time	to delay syncing files
     kern.dirdelay    29	   time	to delay syncing directories
     kern.metadelay   28	   time	to delay syncing metadata

SEE ALSO
     sync(2), fsck(8), sync(8),	sysctl(8)

HISTORY
     The syncer	process	is a descendant	of the `update'	command, which
     appeared in Version 6 AT&T	UNIX, and was usually started by /etc/rc when
     the system	went multi-user.  A kernel initiated `update' process first
     appeared in FreeBSD 2.0.

BUGS
     It	is possible on some systems that a sync(2) occurring simultaneously
     with a crash may cause file system	damage.	 See fsck(8).

FreeBSD	9.3			 July 14, 2000			   FreeBSD 9.3

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | HISTORY | BUGS

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