update - Periodically updates the superblock
The update command executes a sync system call every 30 seconds. This ensures that the file system is up to date in the event of a system crash. This command is provided as a statically-linked executable in /sbin.
The cron program also provides the functionality of the
update command. The update shell script typically provides the
sleep 30 done & exit 0
Specifies the command path
Commands: cron(8), init(8), sync(8)
Functions: sync(2) delim off