# Migrating to a Newer Yocto Project Release

This chapter provides information you can use to migrate work to a newer Yocto Project release. You can find the same information in the release notes for a given release.

## General Migration Considerations

Some considerations are not tied to a specific Yocto Project release. This section presents information you should consider when migrating to any new Yocto Project release.

- Dealing with Customized Recipes: Issues could arise if you take older recipes that contain customizations and simply copy them forward expecting them to work after you migrate to new Yocto Project metadata. For example, suppose you have a recipe in your layer that is a customized version of a core recipe copied from the earlier release, rather than through the use of an append file. When you migrate to a newer version of Yocto Project, the metadata (e.g. perhaps an include file used by the recipe) could have changed in a way that would break the build. Say, for example, a function is removed from an include file and the customized recipe tries to call that function.

  You could "forward-port" all your customizations in your recipe so that everything works for the new release. However, this is not the optimal solution as you would have to repeat this process with each new release if changes occur that give rise to problems.

  The better solution (where practical) is to use append files (`*.bbappend`) to capture any customizations you want to make to a recipe. Doing so, isolates your changes from the main recipe making them much more manageable. However, sometimes it is not practical to use an append file. A good example of this is when introducing a newer or older version of a recipe in another layer.

- Updating Append Files: Since append files generally only contain your customizations, they often do not need to be adjusted for new releases. However, if the `.bbappend` file is specific to a particular version of the recipe (i.e. its name does not use the % wildcard) and the version of the recipe to which it is appending has changed, then you will at a minimum need to rename the append file to match the name of the recipe file. A mismatch between an append file and its corresponding recipe file (`.bb`) will trigger an error during parsing.

  Depending on the type of customization the append file applies, other incompatibilities might occur when you upgrade. For example, if your append file applies a patch and the recipe to which it is appending is updated to a newer version, the patch might no longer apply. If this is the case and assuming the patch is still needed, you must modify the patch file so that it does apply.

## Moving to the Yocto Project 1.3 Release

This section provides migration information for moving to the Yocto Project 1.3 Release from the prior release.

### Local Configuration

Differences include changes for `SSTATE_MIRRORS` and `bblayers.conf`.

#### SSTATE_MIRRORS

The shared state cache (sstate-cache), as pointed to by `SSTATE_DIR`, by default now has two-character subdirectories to prevent issues arising from too many files in the same directory. Also, native sstate-cache packages will go into a subdirectory named using the distro ID string. If you copy the newly structured sstate-cache to a mirror location (either local or remote) and then point to it in `SSTATE_MIRRORS`, you need to append "PATH" to the end of the mirror URL so that the path used by BitBake before the mirror substitution is appended to the path used to access the mirror. Here is an example:

         SSTATE_MIRRORS = "file://.* http://someserver.tld/share/sstate/PATH"

#### bblayers.conf

The `meta-yocto` layer consists of two parts that correspond to the Poky reference distribution and the reference hardware Board Support Packages (BSPs), respectively: `meta-yocto` and `meta-yocto-bsp`. When running BitBake or Hob for the first time after upgrading, your `conf/bblayers.conf` file will be updated to handle this change and you will be asked to re-run or restart for the changes to take effect.

### Recipes

Differences include changes for the following:

- Python function whitespace

- `proto=` in `SRC_URI`

- `nativesdk`

- Task recipes

- `IMAGE_FEATURES`

- Removed recipes

#### Python Function Whitespace

All Python functions must now use four spaces for indentation. Previously, an inconsistent mix of spaces and tabs existed, which made extending these functions using `_append` or `_prepend` complicated given that Python treats whitespace as syntactically significant. If you are defining or extending any Python functions (e.g. `populate_packages`, `do_unpack`, `do_patch` and so forth) in custom recipes or classes, you need to ensure you are using consistent four-space indentation.

#### proto= in SRC_URI

Any use of `proto=` in `SRC_URI` needs to be changed to `protocol=`. In particular, this applies to the following URIs:

- `svn://`

- `bzr://`

- `hg://`

- `osc://`

Other URIs were already using `protocol=`. This change improves consistency.

#### nativesdk

The suffix `nativesdk` is now implemented as a prefix, which simplifies a lot of the packaging code for `nativesdk` recipes. All custom `nativesdk` recipes and any references need to be updated to use `nativesdk-*` instead of `*-nativesdk`.

#### Task Recipes

"Task" recipes are now known as "Package groups" and have been renamed from `task-*.bb` to `packagegroup-*.bb`. Existing references to the previous `task-*` names should work in most cases as there is an automatic upgrade path for most packages. However, you should update references in your own recipes and configurations as they could be removed in future releases. You should also rename any custom `task-*` recipes to `packagegroup-*`, and change them to inherit `packagegroup` instead of `task`, as well as taking the opportunity to remove anything now handled by `packagegroup.bbclass`, such as providing `-dev` and `-dbg` packages, setting `LIC_FILES_CHKSUM`, and so forth. See the "`packagegroup.bbclass`" section for further details.

#### IMAGE_FEATURES

Image recipes that previously included "apps-console-core" in `IMAGE_FEATURES` should now include "splash" instead to enable the boot-up splash screen. Retaining "apps-console-core" will still include the splash screen but generates a warning. The "apps-x11-core" and "apps-x11-games" `IMAGE_FEATURES` features have been removed.

#### Removed Recipes

The following recipes have been removed. For most of them, it is unlikely that you would have any references to them in your own Metadata. However, you should check your metadata against this list to be sure:

- `libx11-trim`: Replaced by `libx11`, which has a negligible size difference with modern Xorg.

- `xserver-xorg-lite`: Use `xserver-xorg`, which has a negligible size difference when DRI and GLX modules are not installed.

- `xserver-kdrive`: Effectively unmaintained for many years.

- `mesa-xlib`: No longer serves any purpose.

- `galago`: Replaced by telepathy.

- `gail`: Functionality was integrated into GTK+ 2.13.

- `eggdbus`: No longer needed.

- `gcc-*-intermediate`: The build has been restructured to avoid the need for this step.

- `libgsmd`: Unmaintained for many years. Functionality now provided by `ofono` instead.

- contacts, dates, tasks, eds-tools: Largely unmaintained PIM application suite. It has been moved to `meta-gnome` in `meta-openembedded`.

In addition to the previously listed changes, the `meta-demoapps` directory has also been removed because the recipes in it were not being maintained and many had become obsolete or broken. Additionally, these recipes were not parsed in the default configuration. Many of these recipes are already provided in an updated and maintained form within the OpenEmbedded community layers such as `meta-oe` and `meta-gnome`. For the remainder, you can now find them in the `meta-extras` repository, which is in the Yocto Project Source Repositories.

### Linux Kernel Naming

The naming scheme for kernel output binaries has been changed to now include `PE` as part of the filename:

         KERNEL_IMAGE_BASE_NAME ?= "${KERNEL_IMAGETYPE}-${PE}-${PV}-${PR}-${MACHINE}-${DATETIME}"

Because the `PE` variable is not set by default, these binary files could result with names that include two dash characters. Here is an example:

         bzImage--3.10.9+git0+cd502a8814_7144bcc4b8-r0-qemux86-64-20130830085431.bin

## Moving to the Yocto Project 1.4 Release

This section provides migration information for moving to the Yocto Project 1.4 Release from the prior release.

### BitBake

Differences include the following:

- Comment Continuation: If a comment ends with a line continuation (\) character, then the next line must also be a comment. Any instance where this is not the case, now triggers a warning. You must either remove the continuation character, or be sure the next line is a comment.

- Package Name Overrides: The runtime package specific variables `RDEPENDS`, `RRECOMMENDS`, `RSUGGESTS`, `RPROVIDES`, `RCONFLICTS`, `RREPLACES`, `FILES`, `ALLOW_EMPTY`, and the pre, post, install, and uninstall script functions `pkg_preinst`, `pkg_postinst`, `pkg_prerm`, and `pkg_postrm` should always have a package name override. For example, use `RDEPENDS_${PN}` for the main package instead of `RDEPENDS`. BitBake uses more strict checks when it parses recipes.

### Build Behavior

Differences include the following:

- Shared State Code: The shared state code has been optimized to avoid running unnecessary tasks. For example, `bitbake -c rootfs some-image` from shared state no longer populates the target sysroot since that is not necessary. Instead, the system just needs to extract the output package contents, re-create the packages, and construct the root filesystem. This change is unlikely to cause any problems unless you have missing declared dependencies.

- Scanning Directory Names: When scanning for files in `SRC_URI`, the build system now uses `FILESOVERRIDES` instead of `OVERRIDES` for the directory names. In general, the values previously in `OVERRIDES` are now in `FILESOVERRIDES` as well. However, if you relied upon an additional value you previously added to `OVERRIDES`, you might now need to add it to `FILESOVERRIDES` unless you are already adding it through the `MACHINEOVERRIDES` or `DISTROOVERRIDES` variables, as appropriate. For more related changes, see the "Variables" section.

### Proxies and Fetching Source

A new `oe-git-proxy` script has been added to replace previous methods of handling proxies and fetching source from Git. See the `meta-yocto/conf/site.conf.sample` file for information on how to use this script.

### Custom Interfaces File (netbase change)

If you have created your own custom `etc/network/interfaces` file by creating an append file for the `netbase` recipe, you now need to create an append file for the `init-ifupdown` recipe instead, which you can find in the Source Directory at `meta/recipes-core/init-ifupdown`. For information on how to use append files, see the "Using .bbappend Files" in the Yocto Project Development Manual.

### Remote Debugging

Support for remote debugging with the Eclipse IDE is now separated into an image feature (`eclipse-debug`) that corresponds to the `packagegroup-core-eclipse-debug` package group. Previously, the debugging feature was included through the `tools-debug` image feature, which corresponds to the `packagegroup-core-tools-debug` package group.

### Variables

The following variables have changed:

- `SANITY_TESTED_DISTROS`: This variable now uses a distribution ID, which is composed of the host distributor ID followed by the release. Previously, `SANITY_TESTED_DISTROS` was composed of the description field. For example, "Ubuntu 12.10" becomes "Ubuntu-12.10". You do not need to worry about this change if you are not specifically setting this variable, or if you are specifically setting it to "".

- `SRC_URI`: The `${` `PN` `}`, `${` `PF` `}`, `${` `P` `}`, and `FILE_DIRNAME` directories have been dropped from the default value of the `FILESPATH` variable, which is used as the search path for finding files referred to in `SRC_URI`. If you have a recipe that relied upon these directories, which would be unusual, then you will need to add the appropriate paths within the recipe or, alternatively, rearrange the files. The most common locations are still covered by `${BP}`, `${BPN}`, and "files", which all remain in the default value of `FILESPATH`.

### Target Package Management with RPM

If runtime package management is enabled and the RPM backend is selected, Smart is now installed for package download, dependency resolution, and upgrades instead of Zypper. For more information on how to use Smart, run the following command on the target:

         smart --help

### Recipes Moved

The following recipes were moved from their previous locations because they are no longer used by anything in the OpenEmbedded-Core:

- `clutter-box2d`: Now resides in the `meta-oe` layer.

- `evolution-data-server`: Now resides in the `meta-gnome` layer.

- `gthumb`: Now resides in the `meta-gnome` layer.

- `gtkhtml2`: Now resides in the `meta-oe` layer.

- `gupnp`: Now resides in the `meta-multimedia` layer.

- `gypsy`: Now resides in the `meta-oe` layer.

- `libcanberra`: Now resides in the `meta-gnome` layer.

- `libgdata`: Now resides in the `meta-gnome` layer.

- `libmusicbrainz`: Now resides in the `meta-multimedia` layer.

- `metacity`: Now resides in the `meta-gnome` layer.

- `polkit`: Now resides in the `meta-oe` layer.

- `zeroconf`: Now resides in the `meta-networking` layer.

### Removals and Renames

The following list shows what has been removed or renamed:

- `evieext`: Removed because it has been removed from `xserver` since 2008.

- Gtk+ DirectFB: Removed support because upstream Gtk+ no longer supports it as of version 2.18.

- `libxfontcache / xfontcacheproto`: Removed because they were removed from the Xorg server in 2008.

- `libxp / libxprintapputil / libxprintutil / printproto`: Removed because the XPrint server was removed from Xorg in 2008.

- `libxtrap / xtrapproto`: Removed because their functionality was broken upstream.

- linux-yocto 3.0 kernel: Removed with linux-yocto 3.8 kernel being added. The linux-yocto 3.2 and linux-yocto 3.4 kernels remain as part of the release.

- `lsbsetup`: Removed with functionality now provided by `lsbtest`.

- `matchbox-stroke`: Removed because it was never more than a proof-of-concept.

- `matchbox-wm-2 / matchbox-theme-sato-2`: Removed because they are not maintained. However, `matchbox-wm` and `matchbox-theme-sato` are still provided.

- `mesa-dri`: Renamed to `mesa`.

- `mesa-xlib`: Removed because it was no longer useful.

- `mutter`: Removed because nothing ever uses it and the recipe is very old.

- `orinoco-conf`: Removed because it has become obsolete.

- `update-modules`: Removed because it is no longer used. The kernel module `postinstall` and `postrm` scripts can now do the same task without the use of this script.

- `web`: Removed because it is not maintained. Superseded by `web-webkit`.

- `xf86bigfontproto`: Removed because upstream it has been disabled by default since 2007. Nothing uses `xf86bigfontproto`.

- `xf86rushproto`: Removed because its dependency in `xserver` was spurious and it was removed in 2005.

- `zypper / libzypp / sat-solver`: Removed and been functionally replaced with Smart (`python-smartpm`) when RPM packaging is used and package management is enabled on the target.

## Moving to the Yocto Project 1.5 Release

This section provides migration information for moving to the Yocto Project 1.5 Release from the prior release.

### Host Dependency Changes

The OpenEmbedded build system now has some additional requirements on the host system:

- Python 2.7.3+

- Tar 1.24+

- Git 1.7.8+

- Patched version of Make if you are using 3.82. Most distributions that provide Make 3.82 use the patched version.

If the Linux distribution you are using on your build host does not provide packages for these, you can install and use the Buildtools tarball, which provides an SDK-like environment containing them.

For more information on this requirement, see the "Required Git, tar, and Python Versions" section.

### `atom-pc` Board Support Package (BSP)

The `atom-pc` hardware reference BSP has been replaced by a `genericx86` BSP. This BSP is not necessarily guaranteed to work on all x86 hardware, but it will run on a wider range of systems than the `atom-pc` did.

Additionally, a `genericx86-64` BSP has been added for 64-bit Atom systems.

### BitBake

The following changes have been made that relate to BitBake:

- BitBake now supports a `_remove` operator. The addition of this operator means you will have to rename any items in recipe space (functions, variables) whose names currently contain `_remove_` or end with `_remove` to avoid unexpected behavior.

- BitBake's global method pool has been removed. This method is not particularly useful and led to clashes between recipes containing functions that had the same name.

- The "none" server backend has been removed. The "process" server backend has been serving well as the default for a long time now.

- The `bitbake-runtask` script has been removed.

- `${` `P` `}` and `${` `PF` `}` are no longer added to `PROVIDES` by default in `bitbake.conf`. These version-specific `PROVIDES` items were seldom used. Attempting to use them could result in two versions being built simultaneously rather than just one version due to the way BitBake resolves dependencies.

### QA Warnings

The following changes have been made to the package QA checks:

- If you have customized `ERROR_QA` or `WARN_QA` values in your configuration, check that they contain all of the issues that you wish to be reported. Previous Yocto Project versions contained a bug that meant that any item not mentioned in `ERROR_QA` or `WARN_QA` would be treated as a warning. Consequently, several important items were not already in the default value of `WARN_QA`. All of the possible QA checks are now documented in the "`insane.bbclass`" section.

- An additional QA check has been added to check if `/usr/share/info/dir` is being installed. Your recipe should delete this file within `do_install` if "make install" is installing it.

- If you are using the buildhistory class, the check for the package version going backwards is now controlled using a standard QA check. Thus, if you have customized your `ERROR_QA` or `WARN_QA` values and still wish to have this check performed, you should add "version-going-backwards" to your value for one or the other variables depending on how you wish it to be handled. See the documented QA checks in the "`insane.bbclass`" section.

### Directory Layout Changes

The following directory changes exist:

- Output SDK installer files are now named to include the image name and tuning architecture through the `SDK_NAME` variable.

- Images and related files are now installed into a directory that is specific to the machine, instead of a parent directory containing output files for multiple machines. The `DEPLOY_DIR_IMAGE` variable continues to point to the directory containing images for the current `MACHINE` and should be used anywhere there is a need to refer to this directory. The `runqemu` script now uses this variable to find images and kernel binaries and will use BitBake to determine the directory. Alternatively, you can set the `DEPLOY_DIR_IMAGE` variable in the external environment.

- When buildhistory is enabled, its output is now written under the Build Directory rather than `TMPDIR`. Doing so makes it easier to delete `TMPDIR` and preserve the build history. Additionally, data for produced SDKs is now split by `IMAGE_NAME`.

- The `pkgdata` directory produced as part of the packaging process has been collapsed into a single machine-specific directory. This directory is located under `sysroots` and uses a machine-specific name (i.e. `tmp/sysroots/<machine>/pkgdata`).

### Shortened Git `SRCREV` Values

BitBake will now shorten revisions from Git repositories from the normal 40 characters down to 10 characters within `SRCPV` for improved usability in path and file names. This change should be safe within contexts where these revisions are used because the chances of spatially close collisions is very low. Distant collisions are not a major issue in the way the values are used.

### `IMAGE_FEATURES`

The following changes have been made that relate to `IMAGE_FEATURES`:

- The value of `IMAGE_FEATURES` is now validated to ensure invalid feature items are not added. Some users mistakenly add package names to this variable instead of using `IMAGE_INSTALL` in order to have the package added to the image, which does not work. This change is intended to catch those kinds of situations. Valid `IMAGE_FEATURES` are drawn from `PACKAGE_GROUP` definitions, `COMPLEMENTARY_GLOB` and a new "validitems" varflag on `IMAGE_FEATURES`. The "validitems" varflag change allows additional features to be added if they are not provided using the previous two mechanisms.

- The previously deprecated "apps-console-core" `IMAGE_FEATURES` item is no longer supported. Add "splash" to `IMAGE_FEATURES` if you wish to have the splash screen enabled, since this is all that apps-console-core was doing.

### `/run`

The `/run` directory from the Filesystem Hierarchy Standard 3.0 has been introduced. You can find some of the implications for this change here. The change also means that recipes that install files to `/var/run` must be changed. You can find a guide on how to make these changes here.

### Removal of Package Manager Database Within Image Recipes

The image `core-image-minimal` no longer adds `remove_packaging_data_files` to `ROOTFS_POSTPROCESS_COMMAND`. This addition is now handled automatically when "package-management" is not in `IMAGE_FEATURES`. If you have custom image recipes that make this addition, you should remove the lines, as they are not needed and might interfere with correct operation of postinstall scripts.

### Images Now Rebuild Only on Changes Instead of Every Time

The `do_rootfs` and other related image construction tasks are no longer marked as "nostamp". Consequently, they will only be re-executed when their inputs have changed. Previous versions of the OpenEmbedded build system always rebuilt the image when requested rather when necessary.

### Task Recipes

The previously deprecated `task.bbclass` has now been dropped. For recipes that previously inherited from this class, you should rename them from `task-*` to `packagegroup-*` and inherit packagegroup instead.

For more information, see the "`packagegroup.bbclass`" section.

### BusyBox

By default, we now split BusyBox into two binaries: one that is suid root for those components that need it, and another for the rest of the components. Splitting BusyBox allows for optimization that eliminates the `tinylogin` recipe as recommended by upstream. You can disable this split by setting `BUSYBOX_SPLIT_SUID` to "0".

### Automated Image Testing

A new automated image testing framework has been added through the `testimage*.bbclass` class. This framework replaces the older `imagetest-qemu` framework.

You can learn more about performing automated image tests in the "Performing Automated Runtime Testing" section.

### Build History

Following are changes to Build History:

- Installed package sizes: `installed-package-sizes.txt` for an image now records the size of the files installed by each package instead of the size of each compressed package archive file.

- The dependency graphs (`depends*.dot`) now use the actual package names instead of replacing dashes, dots and plus signs with underscores.

- The `buildhistory-diff` and `buildhistory-collect-srcrevs` utilities have improved command-line handling. Use the `&dash;&dash;help` option for each utility for more information on the new syntax.

For more information on Build History, see the "Maintaining Build Output Quality" section.

### `udev`

Following are changes to `udev`:

- `udev` no longer brings in `udev-extraconf` automatically through `RRECOMMENDS`, since this was originally intended to be optional. If you need the extra rules, then add `udev-extraconf` to your image.

- `udev` no longer brings in `pciutils-ids` or `usbutils-ids` through `RRECOMMENDS`. These are not needed by `udev` itself and removing them saves around 350KB.

### Removed and Renamed Recipes

- The `linux-yocto` 3.2 kernel has been removed.

- `libtool-nativesdk` has been renamed to `nativesdk-libtool`.

- `tinylogin` has been removed. It has been replaced by a suid portion of Busybox. See the "BusyBox" section for more information.

- `external-python-tarball` has been renamed to `buildtools-tarball`.

- `web-webkit` has been removed. It has been functionally replaced by `midori`.

- `imake` has been removed. It is no longer needed by any other recipe.

- `transfig-native` has been removed. It is no longer needed by any other recipe.

- `anjuta-remote-run` has been removed. Anjuta IDE integration has not been officially supported for several releases.

### Other Changes

Following is a list of short entries describing other changes:

- `run-postinsts`: Make this generic.

- `base-files`: Remove the unnecessary `media/xxx` directories.

- `alsa-state`: Provide an empty `asound.conf` by default.

- `classes/image`: Ensure `BAD_RECOMMENDATIONS` supports pre-renamed package names.

- `classes/rootfs_rpm`: Implement `BAD_RECOMMENDATIONS` for RPM.

- `systemd`: Remove `systemd_unitdir` if `systemd` is not in `DISTRO_FEATURES`.

- `systemd`: Remove `init.d` dir if `systemd` unit file is present and `sysvinit` is not a distro feature.

- `libpam`: Deny all services for the `OTHER` entries.

- `image.bbclass`: Move `runtime_mapping_rename` to avoid conflict with `multilib`. See `YOCTO #4993` in Bugzilla for more information.

- `linux-dtb`: Use kernel build system to generate the `dtb` files.

- `kern-tools`: Switch from guilt to new `kgit-s2q` tool.

## Moving to the Yocto Project 1.6 Release

This section provides migration information for moving to the Yocto Project 1.6 Release from the prior release.

### `archiver` Class

The `archiver` class has been rewritten and its configuration has been simplified. For more details on the source archiver, see the "Maintaining Open Source License Compliance During Your Product's Lifecycle" section in the Yocto Project Development Manual.

### Packaging Changes

The following packaging changes have been made:

- The `binutils` recipe no longer produces a `binutils-symlinks` package. `update-alternatives` is now used to handle the preferred `binutils` variant on the target instead.

- The tc (traffic control) utilities have been split out of the main `iproute2` package and put into the `iproute2-tc` package.

- The `gtk-engines` schemas have been moved to a dedicated `gtk-engines-schemas` package.

- The `armv7a` with thumb package architecture suffix has changed. The suffix for these packages with the thumb optimization enabled is "t2" as it should be. Use of this suffix was not the case in the 1.5 release. Architecture names will change within package feeds as a result.

### BitBake

The following changes have been made to BitBake.

#### Matching Branch Requirement for Git Fetching

When fetching source from a Git repository using `SRC_URI`, BitBake will now validate the `SRCREV` value against the branch. You can specify the branch using the following form:

         SRC_URI = "git://server.name/repository;branch=<branchname>"

If you do not specify a branch, BitBake looks in the default "master" branch.

Alternatively, if you need to bypass this check (e.g. if you are fetching a revision corresponding to a tag that is not on any branch), you can add ";nobranch=1" to the end of the URL within `SRC_URI`.

#### Python Definition substitutions

BitBake had some previously deprecated Python definitions within its `bb` module removed. You should use their sub-module counterparts instead:

- `bb.MalformedUrl`: Use `bb.fetch.MalformedUrl`.

- `bb.fetch.encodeurl`: Use `bb.fetch.encodeurl`.

- `bb.decodeurl`: Use `bb.fetch.decodeurl`

- `bb.mkdirhier`: Use `bb.utils.mkdirhier`.

- `bb.movefile`: Use `bb.utils.movefile`.

- `bb.copyfile`: Use `bb.utils.copyfile`.

- `bb.which`: Use `bb.utils.which`.

- `bb.vercmp_string`: Use `bb.utils.vercmp_string`.

- `bb.vercmp`: Use `bb.utils.vercmp`.

#### SVK Fetcher

The SVK fetcher has been removed from BitBake.

#### Console Output Error Redirection

The BitBake console UI will now output errors to `stderr` instead of `stdout`. Consequently, if you are piping or redirecting the output of `bitbake` to somewhere else, and you wish to retain the errors, you will need to add `2>&1` (or something similar) to the end of your `bitbake` command line.

#### `task-<taskname>` Overrides

`task-<taskname>` overrides have been adjusted so that tasks whose names contain underscores have the underscores replaced by hyphens for the override so that they now function properly. For example, the task override for `do_populate_sdk` is `task-populate-sdk`.

### Changes to Variables

The following variables have changed. For information on the OpenEmbedded build system variables, see the "Variables Glossary" Chapter.

#### `TMPDIR`

`TMPDIR` can no longer be on an NFS mount. NFS does not offer full POSIX locking and inode consistency and can cause unexpected issues if used to store `TMPDIR`.

The check for this occurs on startup. If `TMPDIR` is detected on an NFS mount, an error occurs.

#### `PRINC`

The `PRINC` variable has been deprecated and triggers a warning if detected during a build. For `PR` increments on changes, use the PR service instead. You can find out more about this service in the "Working With a PR Service" section in the Yocto Project Development Manual.

#### `IMAGE_TYPES`

The "sum.jffs2" option for `IMAGE_TYPES` has been replaced by the "jffs2.sum" option, which fits the processing order.

#### `COPY_LIC_MANIFEST`

The `COPY_LIC_MANIFEST` variable must now be set to "1" rather than any value in order to enable it.

#### `COPY_LIC_DIRS`

The `COPY_LIC_DIRS` variable must now be set to "1" rather than any value in order to enable it.

#### `PACKAGE_GROUP`

The `PACKAGE_GROUP` variable has been renamed to `FEATURE_PACKAGES` to more accurately reflect its purpose. You can still use `PACKAGE_GROUP` but the OpenEmbedded build system produces a warning message when it encounters the variable.

### Directory Layout Changes

The `meta-hob` layer has been removed from the top-level of the Source Directory. The contents of this layer are no longer needed by the Hob user interface for building images and toolchains.

### Package Test (ptest)

Package Tests (ptest) are built but not installed by default. For information on using Package Tests, see the "Setting up and running package test (ptest)" section in the Yocto Project Development Manual. For information on the `ptest` class, see the "`ptest.bbclass`" section.

### Build Changes

Separate build and source directories have been enabled by default for selected recipes where it is known to work (a whitelist) and for all recipes that inherit the `cmake` class. In future releases the `autotools` class will enable a separate build directory by default as well. Recipes building Autotools-based software that fails to build with a separate build directory should be changed to inherit from the `autotools-brokensep` class instead of the `autotools` class.

### `qemu-native`

`qemu-native` now builds without SDL-based graphical output support by default. The following additional lines are needed in your `local.conf` to enable it:

         PACKAGECONFIG_pn-qemu-native = "sdl"
         ASSUME_PROVIDED += "libsdl-native"

The default `local.conf` contains these statements. Consequently, if you are building a headless system and using a default `local.conf` file, you will need comment these two lines out.

### `core-image-basic`

`core-image-basic` has been renamed to `core-image-full-cmdline`.

In addition to `core-image-basic` being renamed, `packagegroup-core-basic` has been renamed to `packagegroup-core-full-cmdline` to match.

### Licensing

The top-level `LICENSE` file has been changed to better describe the license of the various components of OE-Core. However, the licensing itself remains unchanged.

Normally, this change would not cause any side-effects. However, some recipes point to this file within `LIC_FILES_CHKSUM` (as `${COREBASE}/LICENSE`) and thus the accompanying checksum must be changed from 3f40d7994397109285ec7b81fdeb3b58 to 4d92cd373abda3937c2bc47fbc49d690. A better alternative is to have `LIC_FILES_CHKSUM` point to a file describing the license that is distributed with the source that the recipe is building, if possible, rather than pointing to `${COREBASE}/LICENSE`.

### `CFLAGS` Options

The "-fpermissive" option has been removed from the default `CFLAGS` value. You need to take action on individual recipes that fail when building with this option. You need to either patch the recipes to fix the issues reported by the compiler, or you need to add "-fpermissive" to `CFLAGS` in the recipes.

### Custom Image Output Types

Custom image output types, as selected using `IMAGE_FSTYPES`, must declare their dependencies on other image types (if any) using a new `IMAGE_TYPEDEP` variable.

### Tasks

The `do_package_write` task has been removed. The task is no longer needed.

### `update-alternative` Provider

The default `update-alternatives` provider has been changed from `opkg` to `opkg-utils`. This change resolves some troublesome circular dependencies. The runtime package has also been renamed from `update-alternatives-cworth` to `update-alternatives-opkg`.

### `virtclass` Overrides

The `virtclass` overrides are now deprecated. Use the equivalent class overrides instead (e.g. `virtclass-native` becomes `class-native`.)

### Removed and Renamed Recipes

The following recipes have been removed:

- `packagegroup-toolset-native` - This recipe is largely unused.

- `linux-yocto-3.8` - Support for the Linux yocto 3.8 kernel has been dropped. Support for the 3.10 and 3.14 kernels have been added with the `linux-yocto-3.10` and `linux-yocto-3.14` recipes.

- `ocf-linux` - This recipe has been functionally replaced using `cryptodev-linux`.

- `genext2fs` - `genext2fs` is no longer used by the build system and is unmaintained upstream.

- `js` - This provided an ancient version of Mozilla's javascript engine that is no longer needed.

- `zaurusd` - The recipe has been moved to the `meta-handheld` layer.

- `eglibc 2.17` - Replaced by the `eglibc 2.19` recipe.

- `gcc 4.7.2` - Replaced by the now stable `gcc 4.8.2`.

- `external-sourcery-toolchain` - this recipe is now maintained in the `meta-sourcery` layer.

- `linux-libc-headers-yocto 3.4+git` - Now using version 3.10 of the `linux-libc-headers` by default.

- `meta-toolchain-gmae` - This recipe is obsolete.

- `packagegroup-core-sdk-gmae` - This recipe is obsolete.

- `packagegroup-core-standalone-gmae-sdk-target` - This recipe is obsolete.

### Removed Classes

The following classes have become obsolete and have been removed:

- `module_strip`

- `pkg_metainfo`

- `pkg_distribute`

- `image-empty`

### Reference Board Support Packages (BSPs)

The following reference BSPs changes occurred:

- The BeagleBoard (`beagleboard`) ARM reference hardware has been replaced by the BeagleBone (`beaglebone`) hardware.

- The RouterStation Pro (`routerstationpro`) MIPS reference hardware has been replaced by the EdgeRouter Lite (`edgerouter`) hardware.

The previous reference BSPs for the `beagleboard` and `routerstationpro` machines are still available in a new `meta-yocto-bsp-old` layer in the Source Repositories at http://git.yoctoproject.org/cgit/cgit.cgi/meta-yocto-bsp-old/.