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       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.

              Print  version  information  on  standard  output,   then   exit

       --     Terminate option list.


       The  variables  LANG,  LC_ALL, LC_CTYPE, and LC_MESSAGES have the usual




       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)


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