sync - update satellite file system
I-nodes are structures that describe that characteristics and contents
of disk files. While a file is open, a copy of its i-node is kept in
system memory. Data routinely get written to disk either when a
buffer is full or when
is called. However, i-nodes on the disk are not updated until the
file is closed.
causes modified i-nodes in memory to be written to disk without having
to close files.