dwww Home | Manual pages | Find package

SYNC(8)                    Linux Programmer's Manual                   SYNC(8)

NAME
       sync - synchronize data on disk with memory

SYNOPSIS
       sync [--help] [--version]

DESCRIPTION
       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 man-
       ner (e.g., before causing a kernel  panic  when  debugging  new  kernel
       code).   In  general,  the  processor  should be halted using the shut-
       down(8) or reboot(8) or halt(8) commands, which will attempt to put the
       system in a quiescent state before calling sync(2).  (Various implemen-
       tations of these commands exist; consult your  documentation;  on  some
       systems one should not call reboot(8) and halt(8) directly.)

OPTIONS
       --help Print a usage message on standard output and exit successfully.

       --version
              Print version information on standard output, then exit success-
              fully.

       --     Terminate option list.

ENVIRONMENT
       The variables LANG, LC_ALL, LC_CTYPE, and LC_MESSAGES  have  the  usual
       meaning.

CONFORMING TO
       POSIX.2.

NOTES
       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.

SEE ALSO
       sync(2), halt(8), reboot(8), update(8)

COLOPHON
       This  page  is  part of release 3.27 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)

Generated by dwww version 1.11.3 on Mon Nov 24 14:29:23 CET 2014.