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, usu
- ally processing 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 directo
- ries
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.