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# rel

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Release resource file

## Description

The release resource file specifies which applications are included in a release (system) based on Erlang/OTP.

This file is used by the functions in `systools` when generating start scripts (`.script`, `.boot`) and release upgrade files (`relup`).

## File Syntax

The release resource file is to be called `Name.rel`.

The `.rel` file contains one single Erlang term, which is called a release specification. The file has the following syntax:

    {release, {RelName,Vsn}, {erts, EVsn},
      [{Application, AppVsn} |
       {Application, AppVsn, Type} |
       {Application, AppVsn, IncApps} |
       {Application, AppVsn, Type, IncApps}]}.

- `RelName = string()` - Release name.

- `Vsn = string()` - Release version.

- `EVsn = string()` - ERTS version the release is intended for.

- `Application = atom()` - Name of an application included in the release.

- `AppVsn = string()` - Version of an application included in the release.

- `Type = permanent | transient | temporary | load | none` - Start type of an application included in the release.

  If `Type = permanent | transient | temporary`, the application is loaded and started in the corresponding way, see `application`.

  If `Type = load`, the application is only loaded.

  If `Type = none`, the application is not loaded and not started, although the code for its modules is loaded.

  Defaults to `permanent`

- `IncApps = [atom()]` - A list of applications that are included by an application included in the release. The list must be a subset of the included applications specified in the application resource file (`Application.app`) and overrides this value. Defaults to the same value as in the application resource file.

#### Note

The list of applications must contain the Kernel and STDLIB applications.

## See Also

`application`, `relup(4)`, `systools`

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