.TH relup 5 "sasl 2.2.1" "Ericsson AB" "Files"
.SH NAME
relup \- Release upgrade file
.SH DESCRIPTION
.LP
The \fIrelease upgrade file\fR\& describes how a release is upgraded in a running system\&.
.LP
This file is automatically generated by \fIsystools:make_relup/3,4\fR\&, using a release resource file (\fI\&.rel\fR\&), application resource files (\fI\&.app\fR\&) and application upgrade files (\fI\&.appup\fR\&) as input\&.
.SH "FILE SYNTAX"

.LP
In a target system, the release upgrade file should be located in the \fIOTP_ROOT/erts-EVsn/Vsn\fR\& directory\&.
.LP
The \fIrelup\fR\& file contains one single Erlang term, which defines the instructions used to upgrade the release\&. The file has the following syntax:
.LP
.nf

{Vsn,
  [{UpFromVsn, Descr, Instructions}, ...],
  [{DownToVsn, Descr, Instructions}, ...]}.
    
.fi
.RS 2
.TP 2
*
\fIVsn = string()\fR\& is the current version of the release\&.
.LP
.TP 2
*
\fIUpFromVsn = string()\fR\& is an earlier version of the release to upgrade from\&.
.LP
.TP 2
*
\fIDescr = term()\fR\& is a user defined parameter passed from the \fIsystools:make_relup/3,4\fR\& function\&. It will be used in the return value of \fIrelease_handler:install_release/1,2\fR\&\&.
.LP
.TP 2
*
\fIInstructions\fR\& is a list of low-level release upgrade instructions, see \fIappup(5)\fR\&\&.
.RS 2
.LP
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\&.
.RE

.LP
.TP 2
*
\fIDownToVsn = string()\fR\& is an earlier version of the release to downgrade to\&.
.LP
.RE

.LP
When upgrading from \fIUpFromVsn\fR\& with \fIrelease_handler:install_release/1,2\fR\&, there does not have to be an exact match of versions, but \fIUpFromVsn\fR\& can be a sub-string of the current release version\&.
.SH "SEE ALSO"

.LP
app(5), appup(5), rel(5), release_handler(3erl), systools(3erl)