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       relup - Release upgrade file


       The  release  upgrade  file  describes  how  a release is upgraded in a
       running system.

       This file is automatically generated by systools:make_relup/3,4,  using
       a release resource file ( .rel), application resource files ( .app) and
       application upgrade files ( .appup) as input.


       In a target system, the release upgrade file should be located  in  the
       OTP_ROOT/erts-EVsn/Vsn directory.

       The  relup  file  contains  one  single  Erlang term, which defines the
       instructions used to upgrade the release. The file  has  the  following

         [{UpFromVsn, Descr, Instructions}, ...],
         [{DownToVsn, Descr, Instructions}, ...]}.

         * Vsn = string() is the current version of the release. .br .br

         * UpFromVsn  =  string()  is  an  earlier  version  of the release to
           upgrade from. .br .br

         * Descr =  term()  is  a  user  defined  parameter  passed  from  the
           systools:make_relup/3,4  function.  It  will  be used in the return
           value of release_handler:install_release/1,2. .br .br

         * Instructions is a list of low-level release  upgrade  instructions,
           see   appup(4).   .br  .br  It  consists  of  the  release  upgrade
           instructions from the respective application upgrade  files  (high-
           level  instructions  are  translated to low-level instructions), in
           the same order as in the start script. .br .br

         * DownToVsn = string() is  an  earlier  version  of  the  release  to
           downgrade to. .br .br

       When upgrading from UpFromVsn with release_handler:install_release/1,2,
       there does not have to be an exact match of versions, but UpFromVsn can
       be a sub-string of the current release version.


       app(4), appup(4), rel(4), release_handler(3erl), systools(3erl)