---
name: "relup"
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/relup/4"
---

# relup(4)

Release upgrade file

## NAME

relup - 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)](/appup/4.md)*. 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)](/app/4.md)*, *[appup(4)](/appup/4.md)*, *[rel(4)](/rel/4.md)*, *release\_handler*, *systools*