Ubuntu Manpage: zsyncmake - Build control file for zsync(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  downloads;  zsyncmake  constructs  the  appropriate metafile and writes
       filename.zsync in the current directory.

       zsync will need at least one URL from which to download the file content. If the .zsync will  be  in  the
       same directory as the file to download, 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 simple 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 downloads; 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 version of a .gz to the client). Note that this
still doesn't guarantee 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 available. If no URLs are specifies, zsync
looks for a file without the .gz extension and assumes that this will be in the same public 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
efficiency. -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
cryptographic 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/Packages.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 creates 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.mirrorservice.org/sites/ftp.freebsd.org/pub/FreeBSD/ports/distfiles/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 downloading 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>