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RedHat 9 (Linux i386) - man page for sync (redhat section 8)

SYNC(8) 										  SYNC(8)

NAME
       sync - synchronize data on disk with memory

SYNOPSYS
       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 filesystem
       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.)

GNU STANDARD 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 1003.2

NOTES
       On  Linux,  sync is only guaranteed to schedule the dirty blocks for writing; it can actu-
       ally 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.   Mail  corrections  and additions to aeb@cwi.nl.  Report bugs in the program to
       fileutils-bugs@gnu.ai.mit.edu.

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

GNU fileutils 4.0			     1998-11					  SYNC(8)


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