.CD "update \(en periodically write the buffer cache to disk"
.SX "update"
.FL "\fR(none)"
.EY "update &" "Start a process that flushes the cache"
.PP
When the system is booted,
.I update
is started up in the background from 
.I /etc/rc
to issue a 
.SY SYNC
system call every 30 sec.