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). 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.

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