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 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 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).

Debian                                            July 14, 2000                                        SYNCER(4)