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[[migrating-from-ol-versions]]
== Migrating from older Buildroot versions

Some versions have introduced backward incompatibilities. This section
explains those incompatibilities, and for each explains what to do to
complete the migration.

[[br2-external-converting]]
=== Migrating to 2016.11

Before Buildroot 2016.11, it was possible to use only one br2-external
tree at once. With Buildroot 2016.11 came the possibility to use more
than one simultaneously (for details, see xref:outside-br-custom[]).

This however means that older br2-external trees are not usable as-is.
A minor change has to be made: adding a name to your br2-external tree.

This can be done very easily in just a few steps:

 * First, create a new file named +external.desc+, at the root of your
   br2-external tree, with a single line defining the name of your
   br2-external tree:
+
----
$ echo 'name: NAME_OF_YOUR_TREE' >external.desc
----
+
.Note
Be careful when choosing a name: It has to be unique and be made
with only ASCII characters from the set +[A-Za-z0-9_]+.

 * Then, change every occurence of +BR2_EXTERNAL+ in your br2-external
   tree with the new variable:
+
----
$ find . -type f | xargs sed -i 's/BR2_EXTERNAL/BR2_EXTERNAL_NAME_OF_YOUR_TREE_PATH/g'
----

Now, your br2-external tree can be used with Buildroot 2016.11 onward.

.Note:
This change makes your br2-external tree incompatible with Buildroot
before 2016.11.

[[migrating-host-usr]]
=== Migrating to 2017.08

Before Buildroot 2017.08, host packages were installed in +$(HOST_DIR)/usr+
(with e.g. the autotools' +--prefix=$(HOST_DIR)/usr+). With Buildroot
2017.08, they are now installed directly in +$(HOST_DIR)+.

Whenever a package installs an executable that is linked with a library
in +$(HOST_DIR)/lib+, it must have an RPATH pointing to that directory.

An RPATH pointing to +$(HOST_DIR)/usr/lib+ is no longer accepted.