Migration notes for 3.4 (honister)

This section provides migration information for moving to the Yocto Project 3.4 Release (codename “honister”) from the prior release.

Override syntax changes

In this release, the : character replaces the use of _ to refer to an override, most commonly when making a conditional assignment of a variable. This means that an entry like:

SRC_URI_qemux86 = "file://somefile"

now becomes:

SRC_URI:qemux86 = "file://somefile"

since qemux86 is an override. This applies to any use of override syntax, so the following:

SRC_URI_append = " file://somefile"
SRC_URI_append_qemux86 = " file://somefile2"
SRC_URI_remove_qemux86-64 = " file://somefile3"
SRC_URI_prepend_qemuarm = "file://somefile4 "
FILES_${PN}-ptest = "${bindir}/xyz"
IMAGE_CMD_tar = "tar"
BASE_LIB_tune-cortexa76 = "lib"
SRCREV_pn-bash = "abc"
BB_TASK_NICE_LEVEL_task-testimage = '0'

would now become:

SRC_URI:append = " file://somefile"
SRC_URI:append:qemux86 = " file://somefile2"
SRC_URI:remove:qemux86-64 = " file://somefile3"
SRC_URI:prepend:qemuarm = "file://somefile4 "
FILES:${PN}-ptest = "${bindir}/xyz"
IMAGE_CMD:tar = "tar"
BASE_LIB:tune-cortexa76 = "lib"
SRCREV:pn-bash = "abc"
BB_TASK_NICE_LEVEL:task-testimage = '0'

This also applies to variable queries to the datastore, for example using getVar and similar so d.getVar("RDEPENDS_${PN}") becomes d.getVar("RDEPENDS:${PN}").

Whilst some of these are fairly obvious such as MACHINE and DISTRO overrides, some are less obvious, for example the packaging variables such as RDEPENDS, FILES and so on taking package names (e.g. ${PN}, ${PN}-ptest) as overrides. These overrides are not always in OVERRIDES but applied conditionally in specific contexts such as packaging. task-<taskname> is another context specific override, the context being specific tasks in that case. Tune overrides are another special case where some code does use them as overrides but some does not. We plan to try and make the tune code use overrides more consistently in the future.

There are some variables which do not use override syntax which include the suffix to variables in layer.conf files such as BBFILE_PATTERN, SRCREV_xxx where xxx is a name from SRC_URI and PREFERRED_VERSION_xxx. In particular, layer.conf suffixes may be the same as a DISTRO override causing some confusion. We do plan to try and improve consistency as these issues are identified.

To help with migration of layers, a script has been provided in OE-Core. Once configured with the overrides used by a layer, this can be run as:

<oe-core>/scripts/contrib/convert-overrides.py <layerdir>


Please read the notes in the script as it isn’t entirely automatic and it isn’t expected to handle every case. In particular, it needs to be told which overrides the layer uses (usually machine and distro names/overrides) and the result should be carefully checked since it can be a little enthusiastic and will convert references to _append, _remove and _prepend in function and variable names.

For reference, this conversion is important as it allows BitBake to more reliably determine what is an override and what is not, as underscores are also used in variable names without intending to be overrides. This should allow us to proceed with other syntax improvements and simplifications for usability. It also means BitBake no longer has to guess and maintain large lookup lists just in case e.g. functionname in my_functionname is an override, and thus should improve efficiency.

New host dependencies

The lz4c, pzstd and zstd commands are now required to be installed on the build host to support LZ4 and Zstandard compression functionality. These are typically provided by lz4 and zstd packages in most Linux distributions. Alternatively they are available as part of buildtools-tarball if your distribution does not provide them. For more information see Required Packages for the Build Host.

Removed recipes

The following recipes have been removed in this release:

  • assimp: problematic from a licensing perspective and no longer needed by anything else

  • clutter-1.0: legacy component moved to meta-gnome

  • clutter-gst-3.0: legacy component moved to meta-gnome

  • clutter-gtk-1.0: legacy component moved to meta-gnome

  • cogl-1.0: legacy component moved to meta-gnome

  • core-image-clutter: removed along with clutter

  • linux-yocto: removed version 5.4 recipes (5.14 and 5.10 still provided)

  • mklibs-native: not actively tested and upstream mklibs still requires Python 2

  • mx-1.0: obsolete (last release 2012) and isn’t used by anything in any known layer

  • packagegroup-core-clutter: removed along with clutter

Removed classes

  • clutter: moved to meta-gnome along with clutter itself

  • image-mklibs: not actively tested and upstream mklibs still requires Python 2

  • meta: no longer useful. Recipes that need to skip installing packages should inherit nopackages instead.

Prelinking disabled by default

Recent tests have shown that prelinking works only when PIE is not enabled (see here and here), and as PIE is both a desirable security feature, and the only configuration provided and tested by the Yocto Project, there is simply no sense in continuing to enable prelink.

There’s also a concern that no one is maintaining the code, and there are open bugs (including this serious one). Given that prelink does intricate address arithmetic and rewriting of binaries the best option is to disable the feature. It is recommended that you consider disabling this feature in your own configuration if it is currently enabled.

Virtual runtime provides

Recipes shouldn’t use the virtual/ string in RPROVIDES and RDEPENDS - it is confusing because virtual/ has no special meaning in RPROVIDES and RDEPENDS (unlike in the corresponding build-time PROVIDES and DEPENDS).

Tune files moved to architecture-specific directories

The tune files found in conf/machine/include have now been moved into their respective architecture name directories under that same location; e.g. x86 tune files have moved into an x86 subdirectory, MIPS tune files have moved into a mips subdirectory, etc. The ARM tunes have an extra level (armv8a, armv8m, etc.) and some have been renamed to make them uniform with the rest of the tunes. See this commit for reference.

If you have any references to tune files (e.g. in custom machine configuration files) they will need to be updated.

Extensible SDK host extension

For a normal SDK, some layers append to TOOLCHAIN_HOST_TASK unconditionally which is fine, until the eSDK tries to override the variable to its own values. Instead of installing packages specified in this variable it uses native recipes instead - a very different approach. This has led to confusing errors when binaries are added to the SDK but not relocated.

To avoid these issues, a new TOOLCHAIN_HOST_TASK_ESDK variable has been created. If you wish to extend what is installed in the host portion of the eSDK then you will now need to set this variable.

Package/recipe splitting

  • perl-cross has been split out from the main perl recipe to its own perlcross recipe for maintenance reasons. If you have bbappends for the perl recipe then these may need extending.

  • The wayland recipe now packages its binaries in a wayland-tools package rather than putting them into wayland-dev.

  • Xwayland has been split out of the xserver-xorg tree and thus is now in its own xwayland recipe. If you need Xwayland in your image then you may now need to add it explicitly.

  • The rpm package no longer has rpm-build in its RRECOMMENDS; if by chance you still need rpm package building functionality in your image and you have not already done so then you should add rpm-build to your image explicitly.

  • The Python statistics standard module is now packaged in its own python3-statistics package instead of python3-misc as previously.

Image / SDK generation changes

  • Recursive dependencies on the do_build task are now disabled when building SDKs. These are generally not needed; in the unlikely event that you do encounter problems then it will probably be as a result of missing explicit dependencies that need to be added.

  • Errors during “complementary” package installation (e.g. for *-dbg and *-dev packages) during image construction are no longer ignored. Historically some of these packages had installation problems, that is no longer the case. In the unlikely event that you see errors as a result, you will need to fix the installation/packaging issues.

  • When building an image, only packages that will be used in building the image (i.e. the first entry in PACKAGE_CLASSES) will be produced if multiple package types are enabled (which is not a typical configuration). If in your CI system you need to have the original behaviour, use bitbake --runall build <target>.

  • The -lic package is no longer automatically added to RRECOMMENDS for every other package when LICENSE_CREATE_PACKAGE is set to “1”. If you wish all license packages to be installed corresponding to packages in your image, then you should instead add the new lic-pkgs feature to IMAGE_FEATURES.


  • Certificates are now properly checked when bitbake fetches sources over HTTPS. If you receive errors as a result for your custom recipes, you will need to use a mirror or address the issue with the operators of the server in question.

  • avahi has had its GTK+ support disabled by default. If you wish to re-enable it, set AVAHI_GTK = "gtk3" in a bbappend for the avahi recipe or in your custom distro configuration file.

  • Setting the BUILD_REPRODUCIBLE_BINARIES variable to “0” no longer uses a strangely old fallback date of April 2011, it instead disables building reproducible binaries as you would logically expect.

  • Setting noexec/nostamp/fakeroot varflags to any value besides “1” will now trigger a warning. These should be either set to “1” to enable, or not set at all to disable.

  • The previously deprecated COMPRESS_CMD and CVE_CHECK_CVE_WHITELIST variables have been removed. Use CONVERSION_CMD and CVE_CHECK_WHITELIST (replaced by CVE_CHECK_IGNORE in version 3.5) respectively instead.

  • The obsolete oe_machinstall function previously provided in the utils class has been removed. For machine-specific installation it is recommended that you use the built-in override support in the fetcher or overrides in general instead.

  • The -P (--clear-password) option can no longer be used with useradd and usermod entries in EXTRA_USERS_PARAMS. It was being implemented using a custom patch to the shadow recipe which clashed with a -P option that was added upstream in shadow version 4.9, and in any case is fundamentally insecure. Hardcoded passwords are still supported but they need to be hashed, see examples in EXTRA_USERS_PARAMS.