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zsyncmake(1)                     File Transfer                    zsyncmake(1)




NAME

       zsyncmake - Build control file for zsync(1)


SYNTAX

       zsyncmake  [  {  -z  |  -Z } ] [ -e ] [ -C ] [ -u url ] [ -U url ] [ -b
       blocksize ] [ -o outfile ] [ -f targetfilename ] [ -v ] filename

       zsync -V


DESCRIPTION

       Constructs a metafile for the zsync client program to  use  to  perform
       partial  file  downloads. filename is the file that users wish to down-
       loads; zsyncmake constructs the appropriate metafile and  writes  file-
       name.zsync in the current directory.

       zsync  will  need at least one URL from which to download the file con-
       tent. If the .zsync will be in the same directory as the file to  down-
       load, you can accept the default - zsync includes a relative URL in the
       control file. If not, use the -u option to specify the URL. You  should
       also  specify  a URL for the uncompressed content with -U if available,
       as zsync can make use of this for more efficient  downloads  sometimes.
       (You  can edit the .zsync file and add these afterwards - it has a sim-
       ple key: value format in the header - but I suggest you  only  do  this
       once you are familiar with the tool.)

       Note  that  zsyncmake  itself  does  not (currently) verify the URLs or
       download any data, you must provide the file data locally and check the
       URLs yourself.


OPTIONS

       -b blocksize
              Specify  the  blocksize  to  the  underlying  rsync algorithm. A
              smaller blocksize may be more efficient for  files  where  there
              are  likely to be lots of small, scattered changes between down-
              loads; a larger blocksize is more efficient for files with fewer
              or  less  scattered  changes.  This blocksize must be a power of
              two. If not specified, zsyncmake chooses one which it thinks  is
              best  for  this file (currently either 2048 or 4096 depending on
              file size) - so normally tyou should not need  to  override  the
              default.

       -C     Tells  zsyncmake  not to generate any instructions in the .zsync
              telling the client to compress the data  it  receives.  This  is
              implied  by  -z,  but this option is here in case you compress a
              file yourself only for the transfer, but want the client to  end
              up with the uncompressed file (e.g. you are transferring an ISO,
              which is held compressed on the server,  but  which  the  client
              cannot  use  unless  it  is uncompressed). Without -C, zsyncmake
              will produce directions for the client to compress the  file  it
              receives  where  appropriate;  -C  is  here  so  you can stop it
              telling the client to do that.

       -e     Tells zsyncmake that the client must  be  able  to  receive  the
              exact  file  that  was  supplied. Without this option, zsyncmake
              only gives a weaker guarantee - that the client will receive the
              data  it  contains (e.g. it might transfer the uncompressed ver-
              sion of a .gz to the client). Note that this still doesn't guar-
              antee  that the client will get it - the client could ignore the
              directives in the zsync file, or might be incapable  of  exactly
              reproducing  the  compression  used.  But  with -e you know that
              zsyncmake has made it possible to get the exact data -  it  will
              exit with an error if it cannot.

       -f filename
              Set the filename to include in the output file (this is what the
              file will be called when a user finished downloading it).

       -o outputfile
              Override the default output file name.

       -u url Specifies the URL from which users can download the  content  of
              the  supplied file. Users need the control file in order to find
              out what parts of the file they already have, and they need  the
              URLs  to  retrieve the parts of the file that they don't already
              have. You can specify multiple URLs by  specifying  -u  multiple
              times.  If  not  specified,  zsync assumes that the file and the
              .zsync will reside in the same public directory, and includes  a
              single relative URL.

       -U url Specifies a URL corresponding to the decompressed content of the
              file (only applicable if it is a gzip file). zsync can sometimes
              download  more  efficiently from the uncompressed data than from
              the compressed data - it will take advantage of this  if  avail-
              able.  If  no URLs are specifies, zsync looks for a file without
              the .gz extension and assumes that this will be in the same pub-
              lic dir as the .zsync, and includes a relative URL to it.

       -v     Enable verbose messages.

       -V     Prints the version of zsync.

       -z     Compress  the  file  to  transfer. Note that this overwrites any
              file called filename.gz without warning (if  you  don't  give  a
              filename,  e.g.  because  you are reading from stdin, then zsync
              will use the name supplied with  -f,  or  as  a  last  fallback,
              zsync-target.gz).

       zsync  can work with compressed data, and, in most cases where the data
       is not already compressed, it is more efficient to compress  it  first.
       While  you can just compress the file to transfer with gzip, if you use
       this option then zsyncmake will compress the file for you, producing  a
       .gz  file  which is optimised for zsync. This can be 30% more efficient
       at download time than compressing with gzip --best - but the compressed
       file will not be as small at that produced by gzip.

       -Z     zsyncmake  automatically  looks inside gzip compressed files and
              exports the underlying, uncompressed data to the zsyncmake file.
              In  testing  this  has  proved to provide greater download effi-
              ciency. -Z overrides the default behaviour and treats gzip files
              as  just  binary data. Use this if it is essential that the user
              receives the compressed data (for  instance  because  a  crypto-
              graphic  signature  is  available only for the compressed data).
              zsync is typically no use if you specify  -Z,  unless  the  gzip
              file  was  compressed with the special --rsync option to make it
              friendly to differential transfers.


EXAMPLES

       zsyncmake                             -C                             -u
       http://ftp.uk.debian.org/debian/dists/sarge/main/binary-i386/Pack-
       ages.gz Packages.gz

       Note use of -C to save the client compressing the file on receipt;  the
       Debian package system uses the file uncompressed.

       zsyncmake -z my-subversion-dump

       In this case there is a large, compressible file to transfer. This cre-
       ates a gzipped version of the file (optimised for zsync), and a  .zsync
       file.  A URL is automatically added assuming that the two files will be
       served from the same directory on the web server.

       zsyncmake            -e            -u             http://www.mirrorser-
       vice.org/sites/ftp.freebsd.org/pub/FreeBSD/ports/dist-
       files/zsync-0.2.2.tar.gz zsync-0.2.2.tar.gz

       This creates a zsync referring to the named source tarball,  which  the
       client  should  download  from the given URL. This example is for down-
       loading a source tarball for a FreeBSD port, hence -e is  specified  so
       the client will be able to match its md5sum.



AUTHORS

       Colin Phipps <cph@moria.org.uk>


SEE ALSO

       zsync(1)



Colin Phipps                          0.6                         zsyncmake(1)

zsync 0.6 - Generated Sun Jan 25 06:36:48 CST 2009
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