sync

Update filesystems to match cached data (UNIX)

Syntax:

sync [node]

Options:

node

(QNX extension) The node to synchronize.

Description:

The sync utility forces the Filesystem Manger (Fsys) to begin flushing all modified in-memory inodes and all previously unwritten system buffers to disk. This ensures that all file modifications up to that point are scheduled to be saved.

Pending data for all disks on the specified node, whether mounted or unmounted, will be queued for draining. If a node isn't specified, the node on which sync is run will be synchronized.

The sync utility usually returns before the operation is complete. After executing sync, you must allow sufficient time for the driver queues to drain before you may assume that the data is safely on disk. This delay depends on the speed of your disk(s), the number of buffers that must be drained, and how active your system is at the time. It is unusual for the operation to take more than four to five seconds with typical IDE drives and a large (2 megabyte) cache, if a large portion of the cache needs to be flushed. With faster disks (e.g. SCSI), it usually completes in under two seconds. If significant amounts of data are being flushed to a floppy disk, it could take many tens of seconds.

Examples:

Synchronize the local filesystem:

    sync

Synchronize the filesystem on node 61:

    sync 61

See also:

shutdown