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sync

flush file system buffers


  1. sync.1.man
  2. sync.2.man
  3. sync.8.man


1. sync.1.man

Manpage of SYNC

SYNC

Section: User Commands (1)
Updated: October 2011
Index Return to Main Contents
 

NAME

sync - flush file system buffers  

SYNOPSIS

sync [OPTION]  

DESCRIPTION

Force changed blocks to disk, update the super block.

--help
display this help and exit
--version
output version information and exit
 

AUTHOR

Written by Jim Meyering.  

REPORTING BUGS

Report sync bugs to bug-coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report sync translation bugs to <http://translationproject.org/team/>  

COPYRIGHT

Copyright © 2011 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.  

SEE ALSO

sync(2)

The full documentation for sync is maintained as a Texinfo manual. If the info and sync programs are properly installed at your site, the command

info coreutils aqsync invocationaq

should give you access to the complete manual.


 

Index

NAME
SYNOPSIS
DESCRIPTION
AUTHOR
REPORTING BUGS
COPYRIGHT
SEE ALSO

This document was created by man2html using the manual pages.
Time: 17:32:39 GMT, October 23, 2013

2. sync.2.man

Manpage of SYNC

SYNC

Section: Linux Programmer's Manual (2)
Updated: 2010-09-20
Index Return to Main Contents
 

NAME

sync - commit buffer cache to disk  

SYNOPSIS

#include <unistd.h>

void sync(void);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

sync():

_BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
 

DESCRIPTION

sync() first commits inodes to buffers, and then buffers to disk.  

ERRORS

This function is always successful.  

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001.  

NOTES

Since glibc 2.2.2 the Linux prototype is as listed above, following the various standards. In libc4, libc5, and glibc up to 2.2.1 it was "int sync(void)", and sync() always returned 0.  

BUGS

According to the standard specification (e.g., POSIX.1-2001), sync() schedules the writes, but may return before the actual writing is done. However, since version 1.3.20 Linux does actually wait. (This still does not guarantee data integrity: modern disks have large caches.)  

SEE ALSO

bdflush(2), fdatasync(2), fsync(2), sync(8), update(8)  

COLOPHON

This page is part of release 3.32 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/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
ERRORS
CONFORMING TO
NOTES
BUGS
SEE ALSO
COLOPHON

This document was created by man2html using the manual pages.
Time: 17:32:39 GMT, October 23, 2013

3. sync.8.man

Manpage of SYNC

SYNC

Section: Linux Programmer's Manual (8)
Updated: 1998-11-01
Index Return to Main Contents
 

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 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.)  

OPTIONS

--help
Print a usage message on standard output and exit successfully.
--version
Print version information on standard output, then exit successfully.
--
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 3.32 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/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
ENVIRONMENT
CONFORMING TO
NOTES
SEE ALSO
COLOPHON

This document was created by man2html using the manual pages.
Time: 17:32:39 GMT, October 23, 2013

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