sync
flush file system buffers
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 buffersSYNOPSIS
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.orgGNU 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
This document was created by man2html using the manual pages.
Time: 17:33:02 GMT, May 11, 2012
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 diskSYNOPSIS
#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
This document was created by man2html using the manual pages.
Time: 17:33:02 GMT, May 11, 2012
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 memorySYNOPSIS
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
This document was created by man2html using the manual pages.
Time: 17:33:02 GMT, May 11, 2012
