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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 is to be located in directory $ROOT/releases/Vsn.

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() - Current release version.

  • UpFromVsn = string() - Earlier version of the release to upgrade from.

  • Descr = term() - A user-defined parameter passed from the function systools:make_relup/3,4. It is used in the return value of release_handler:install_release/1,2.

  • Instructions - A list of low-level release upgrade instructions, see appup(4). 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() - Earlier version of the release to downgrade to.

See Also

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