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update(8) [osx man page]

UPDATE(8)						    BSD System Manager's Manual 						 UPDATE(8)

update -- flush internal filesystem caches to disk frequently SYNOPSIS
The update utility has been incorporated into launchd(8). It historically helped protect the integrity of disk volumes by flushing volatile cached filesystem data to disk at thirty second intervals using the sync(2) function call. SEE ALSO
sync(2), fsck(8), launchd(8), sync(8) BUGS
It is possible on some systems that a sync occurring simultaneously with a crash may cause file system damage. See fsck(8). HISTORY
An update utility appeared in Version 6 AT&T UNIX. BSD
August 18, 2008 BSD

Check Out this Related Man Page

SYNCER(4)                                                  BSD Kernel Interfaces Manual                                                  SYNCER(4)

syncer -- file system synchronizer kernel process SYNOPSIS
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). BSD July 14, 2000 BSD
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