NAME

       relup - Release upgrade file

DESCRIPTION

       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.

FILE SYNTAX

       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 syntax:

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

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

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

         * 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.

         * Instructions is a list of low-level release upgrade instructions, see appup(5).

           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.

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

       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.

SEE ALSO

       app(5), appup(5), rel(5), release_handler(3erl), systools(3erl)