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.
In a target system, the release upgrade file should be located in
the OTP_ROOT/erts-EVsn/Vsn directory.
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() is the current version of the release.UpFromVsn = string() is an earlier version of the release
to upgrade from.Descr = term() is a user defined parameter passed
from the systools:make_relup/3,4 function. It will
be used in the return value of
release_handler:install_release/1,2.Instructions is a list of low-level release upgrade
instructions, see appup(4).DownToVsn = string() is an earlier version of the release
to downgrade to.When upgrading from UpFromVsn with
release_handler:install_release/1,2, there does not have to be
an exact match of versions, but UpFromVsn can be a sub-string
of the current release version.
app(4), appup(4), rel(4), release_handler(3), systools(3)