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  <header>
    <copyright>
      <year>1997</year>
      <year>2021</year>
      <holder>Ericsson AB, All Rights Reserved</holder>
    </copyright>
    <legalnotice>
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
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    </legalnotice>

    <title>relup</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
  </header>
  <file>relup</file>
  <filesummary>Release upgrade file</filesummary>
  <description>
    <p>The <em>release upgrade file</em> describes how a release is
      upgraded in a running system.</p>
    <p>This file is automatically generated by
      <seemfa marker="systools#make_relup/3"><c>systools:make_relup/3,4</c></seemfa>, 
      using a release resource file
      (<c>.rel</c>), application resource files (<c>.app</c>), and
      application upgrade files (<c>.appup</c>) as input.</p>
  </description>

  <section>
    <title>File Syntax</title>
    <p>In a target system, the release upgrade file is to be located in
      directory <c>$ROOT/releases/Vsn</c>.</p>
    <p>The <c>relup</c> file contains one single Erlang term, which
      defines the instructions used to upgrade the release. The file has
      the following syntax:</p>
    <code type="none">
{Vsn,
  [{UpFromVsn, Descr, Instructions}, ...],
  [{DownToVsn, Descr, Instructions}, ...]}.</code>
    <taglist>
      <tag><c>Vsn = string()</c></tag>
        <item><p>Current release version.</p></item>
      <tag><c>UpFromVsn = string()</c></tag>
        <item><p>Earlier version of the release to upgrade from.</p></item>
      <tag><c>Descr = term()</c></tag>
        <item><p>A user-defined parameter passed
          from the function 
	  <seemfa marker="systools#make_relup/3"><c>systools:make_relup/3,4</c></seemfa>.
	  It is used in the return value of
          <seemfa marker="release_handler#install_release/1"><c>release_handler:install_release/1,2</c></seemfa>.</p></item>
      <tag><c>Instructions</c></tag>
        <item><p>A list of low-level release upgrade instructions, see
          <seefile marker="appup"><c>appup(4)</c></seefile>.
          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.</p></item>
      <tag><c>DownToVsn = string()</c></tag>
        <item><p>Earlier version of the release to downgrade to.</p></item>
    </taglist>
  </section>

  <section>
    <title>See Also</title>
    <p><seefile marker="kernel:app"><c>app(4)</c></seefile>,
      <seefile marker="appup"><c>appup(4)</c></seefile>,
      <seefile marker="rel"><c>rel(4)</c></seefile>,
      <seeerl marker="release_handler"><c>release_handler(3)</c></seeerl>,
      <seeerl marker="systools"><c>systools(3)</c></seeerl></p>
  </section>
</fileref>

