# relup

### FILE

relup

### FILE SUMMARY

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(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()` 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(4), appup(4), rel(4), release_handler(3), systools(3)

### AUTHORS

Gunilla Hugosson - support@erlang.ericsson.se

sasl 2.1.5.1
Copyright © 1991-2007 Ericsson AB