FutureMigrationGuide

This page should be used to keep track of items which should be added to the migration guide in the YP Reference Manual. It's a living document for the life of a development cycle and by M4 should represent a significant proportion of items that are worthy of note in the migration guide.
Once the migration guide for a release has been completed the contents of this page should be cleared out.
=3.0 Migration Guide items=
== Init system selection ==
Changing the init system manager previously required setting a number of different variables; this can now be accomplished by setting the INIT_MANAGER variable and corresponding include files (conf/distro/include/init-manager-*.conf); include files are provided for four values - "none", "sysvinit", "systemd" and "mdev-busybox". The default value "none" for INIT_MANAGER should allow your current settings to continue working, but it is advisable to set INIT_MANAGER explicitly.
== LSB support removed ==
LSB as a standard isn't current, and isn't well suited to embedded applications. Support may be continued in a separate layer if needed but at present it has been removed from the core.
Following on from this change, the poky-lsb derivative distribution configuration that was also used for testing alternative configurations has been replaced with a poky-altcfg distribution that has LSB parts removed.
== Removed recipes ==
* core-image-lsb-dev: part of removed LSB support
* core-image-lsb: part of removed LSB support
* core-image-lsb-sdk: part of removed LSB support
* cve-check-tool: functionally replaced by cve-update-db recipe and cve-check class
* eglinfo: no longer maintained. eglinfo from mesa-demos is an adequate and maintained alternative.
* gcc-8.3: version 8.3 removed (replaced by 9.2)
* gnome-themes-standard: only needed by gtk+ 2.x which has been removed.
* gtk+: GTK+ 2 is obsolete (replaced by gtk+3)
* irda-utils: obsolete - IrDA support has been removed from the Linux kernel in version 4.17 and later.
* libnewt-python: libnewt Python support merged into main libnewt recipe
* libsdl: replaced by newer libsdl2
* libx11-diet: obsolete
* libxx86dga: remove obsolete client libary
* libxx86misc: remove this now redundant library
* linux-yocto: version 5.0 removed (5.2 / 4.19 present)
* lsbinitscripts: part of removed LSB support
* lsb: part of removed LSB support
* lsbtest: part of removed LSB support
* openssl10: replaced by newer openssl 1.1
* packagegroup-core-lsb: part of removed LSB support
* python-nose: remove the python 2.x version of the recipe
* python-numpy: remove the python 2.x version of the recipe
* python-scons: remove the python 2.x version of the recipe
* source-highlight: no longer needed
* stress: replaced by stress-ng
* vulkan: split into vulkan-loader, vulkan-headers and vulkan-tools
* weston-conf: functionality moved to weston-init
== Packaging changes ==
* The epiphany browser has been dropped from packagegroup-self-hosted as it has not been needed inside build-appliance-image for a long time and was causing resource problems.
* libcap-ng python support has been moved to a separate libcap-ng-python recipe to streamline the build process when the python bindings aren't needed
* libdrm now packages the amdgpu.ids file into a separate libdrm-amdgpu package
* python3: the runpy module is now in the python3-core package as it is required to support the common "python3 -m" command usage.
* distcc now provides separate distcc-client and distcc-server packages as typically one or the other are needed, rather than both.
* python*-setuptools recipes now separately package the pkg_resources module in a python-pkg-resources / python3-pkg-resources package as the module is useful independent of the rest of the setuptools package. The main python-setuptools / python3-setuptools package depends on this new package so you should only need to update dependencies unless you want to take advantage of the increased granularity.
== CVE checking ==
cve-check-tool has been functionally replaced by a new cve-update-db recipe and functionality built into the cve-check class. The result uses NVD JSON data feeds rather than the deprecated XML feeds that cve-check-tool was using, supports CVSSv3 scoring and makes other improvements.
Additionally, the CVE_CHECK_CVE_WHITELIST variable has been replaced by CVE_CHECK_WHITELIST.
== Bitbake changes ==
* addtask statements now properly validate dependent tasks - previously an invalid task here would be silently ignored, now it will generate a warning.
* Other invalid addtask and deltask usages will now trigger warnings (multiple target tasks arguments with addtask / deltask, multiple before/after clauses)
* The "multiconfig" prefix is now shortened to "mc"; "multiconfig" will continue to work, however it may be removed in a future release.
* bitbake -g no longer generates a recipe-depends.dot file as the contents (a reprocessed version of task-depends.dot) were confusing.
* The bb.build.FuncFailed exception, previously raised by bb.build.exec_func() when certain other exceptions have occurred, has been removed. The real underlying exceptions will be raised instead. If you have calls to bb.build.exec_func() in custom classes or tinfoil-using scripts, any references to bb.build.FuncFailed should be cleaned up.
* Additionally, the bb.build.exec_func() no longer accepts the "pythonexception" parameter - it now always raises exceptions. Remove this argument in any calls to bb.build.exec_func() in custom classes or scripts.
* The BB_SETSCENE_VERIFY_FUNCTION2 is no longer used - in the unlikely event that you have any references to it, they should be removed.
* The RunQueueExecuteScenequeue and RunQueueExecuteTasks events have been removed since setscene tasks are now executed as part of the normal runqueue. Any event handling code in custom classes or scripts that handles these two events will need to be updated.
* The arguments passed to functions used with BB_HASHCHECK_FUNCTION have changed. If you are using own custom hash check function, see http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=40a5e193c4ba45c928fccd899415ea56b5417725 for details.
* Task specifications in BB_TASKDEPDATA and class implementations used in signature generator classes now use "<fn>:<task>" everywhere rather than the "." delimiter that was being used in some places. This makes it consistent with everywhere else in the code. Custom signature generator classes and code that reads BB_TASKDEPDATA will need to be updated to use ':' as a separator rather than '.'.
== Sanity checks ==
* SRC_URI is now checked for usage of two problematic items:
*# "${PN}" - instead "${BPN}" should be used to avoid problems when PN is prefixed or suffixed e.g. with multiconfig.
*# github archive tarballs - these are not guaranteed to be stable and thus it is likely that they will be refreshed and thus the SRC_URI checksums will fail to apply. It is recommended that you fetch either an official release tarball or a specific revision from the actual git repository instead.
*:Either one of these will now trigger a warning by default. If you wish to disable this check, remove src-uri-bad from WARN_QA.
* The file-rdeps runtime dependency check no longer expands RDEPENDS recursively as there is no mechanism to ensure they can be fully computed, and thus races sometimes resulted in errors showing up and sometimes not. Thus you may now see errors for missing runtime dependencies that were previously satisfied recursively e.g. package A contains a shell script starting with #!/bin/bash but has no dependency on bash, but depends on package B that does depend on bash. Add the missing dependency / dependencies to resolve the warning. 
* Setting DEPENDS_${PN} anywhere (typically in a recipe) will now trigger an error - this is invalid, as DEPENDS is not a package-specific variable (unlike RDEPENDS). Set DEPENDS instead.
* systemd is currently known not to work well with the musl C library as upstream only officially supports linking it with glibc. Thus, a warning will now be shown when building systemd in conjunction with musl.
== Miscellaneous ==
* The gnome class has been removed, as it did not do very much anymore. Recipes that previously inherited this class should be updated to do the following:
 inherit gnomebase gtk-icon-cache gconf mime
* The meta/recipes-kernel/linux/linux-dtb.inc file has been removed. It was previously deprecated (in favour of setting KERNEL_DEVICETREE in any kernel recipe) and only produced a warning. Remove any include/require statements pointing to this file.
* TARGET_CFLAGS, TARGET_CPPFLAGS, TARGET_CXXFLAGS, and TARGET_LDFLAGS are no longer exported to the external environment. This has not required changes to any recipes, but if for some reason the software being built by one of your recipes is expecting these variables to be set then it will now fail, and you will need to either export the variable(s) in the recipe or change the scripts so that that isn't necessary.
* The host distro identifier as used in NATIVELSBSTRING (when not using uninative) and SANITY_TESTED_DISTROS is now always lowercased even if it does not contain a version number.
* In the base-files recipe, writing the hostname into /etc/hosts and /etc/hostname is now done within the main do_install function rather than do_install_basefilesissue, so that do_install_basefilesissue can be more easily overridden without having to duplicate the hostname functionality. If you have done the latter (e.g. in a base-files bbappend) then you should remove it from your customised do_install_basefilesissue function.
* The wic --expand command-line option now uses commas to separate key:value pairs rather than hyphens, as was documented in the command-line help. Any scripts or commands where you use wic --expand with multiple key:value pairs will need to be updated.
* UEFI image variable settings have been moved from various places to a central conf/image-uefi.conf. However, this should not influence any existing configuration as the meta/conf/image-uefi.conf in the core metadata sets defaults that can be overridden in the same manner as before.
* conf/distro/include/world-broken.inc has been removed - where we need to disable certain recipes when using the musl C library, individual recipes now have COMPATIBLE_HOST_libc-musl set with a comment explaining why.