---
name: "rel"
section: "4"
platform: "linux"
package: "erlang-core"
version: "29.1.1-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/rel/4"
---

# rel(4)

Release resource file

## NAME

rel - 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)](/relup/4.md)*, *systools*