NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | CONFORMING TO | NOTES | SEE ALSO | COLOPHON
SYNC(8) Linux Programmer's Manual SYNC(8)
sync - synchronize data on disk with memory
sync [--help] [--version]
sync writes any data buffered in memory out to disk. This can include (but is
not limited to) modified superblocks, modified inodes, and delayed reads and
writes. This must be implemented by the kernel; The sync program does nothing
but exercise the sync(2) system call.
The kernel keeps data in memory to avoid doing (relatively slow) disk reads
and writes. This improves performance, but if the computer crashes, data may
be lost or the file system corrupted as a result. sync ensures that
everything in memory is written to disk.
sync should be called before the processor is halted in an unusual manner
(e.g., before causing a kernel panic when debugging new kernel code). In
general, the processor should be halted using the shutdown(8) or reboot(8) or
halt(8) commands, which will attempt to put the system in a quiescent state
before calling sync(2). (Various implementations of these commands exist;
consult your documentation; on some systems one should not call reboot(8) and
halt(8) directly.)
--help Print a usage message on standard output and exit successfully.
--version
Print version information on standard output, then exit successfully.
-- Terminate option list.
The variables LANG, LC_ALL, LC_CTYPE, and LC_MESSAGES have the usual meaning.
POSIX.2.
On Linux, sync is only guaranteed to schedule the dirty blocks for writing; it
can actually take a short time before all the blocks are finally written. The
reboot(8) and halt(8) commands take this into account by sleeping for a few
seconds after calling sync(2).
This page describes sync as found in the fileutils-4.0 package; other versions
may differ slightly.
sync(2), halt(8), reboot(8), update(8)
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 1998-11-01 SYNC(8)