kumquat-buildroot/docs/manual/migrating.txt
Arnout Vandecappelle (Essensium/Mind) f24fb23829 docs/manual/migrating.txt: add section with general migrating tips
This is based on Yann's and Arnout's experience with migrating
Buildroot.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Yann E. MORIN <yann.morin.1998@free.fr>
[yann.morin.1998@free.fr: add "For more details, "]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
2021-08-05 22:01:41 +02:00

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// -*- mode:doc; -*-
// vim: set syntax=asciidoc:
[[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.
[[migrating-approach]]
=== General approach
To migrate from an older Buildroot version, take the following steps.
. For all your configurations, do a build in the old Buildroot
environment. Run +make graph-size+. Save
+graphs/file-size-stats.csv+ in a different location. Run +make
clean+ to remove the rest.
. Review the specific migration notes below and make the required
adaptations to external packages and custom build scripts.
. Update Buildroot.
. Run +make menuconfig+ starting from the existing +.config+.
. If anything is enabled in the Legacy menu, check its help text,
unselect it, and save the configuration.
. For more details, review the git commit messages for the packages that
you need. Change into the +packages+ directory and run
+git log <old version>.. -- <your packages>+.
. Build in the new Buildroot environment.
. Fix build issues in external packages (usually due to updated
dependencies).
. Run +make graph-size+.
. Compare the new +file-size-stats.csv+ with the original one, to
check if no required files have disappeared and if no new big unneeded
files have appeared.
. For configuration (and other) files in a custom overlay that overwrite
files created by Buildroot, check if there are changes in the
Buildroot-generated file that need to be propagated to your custom
file.
[[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.