%poky; ] > This appendix presents customizations you can apply to both the standard and extensible SDK. Each subsection identifies the type of SDK to which the section applies.

The extensible SDK primarily consists of a pre-configured copy of the OpenEmbedded build system from which it was produced. Thus, the SDK's configuration is derived using that build system and the following filters, which the OpenEmbedded build system applies against local.conf and auto.conf if they are present: Variables whose values start with "/" are excluded since the assumption is that those values are paths that are likely to be specific to the build host. Variables listed in SDK_LOCAL_CONF_BLACKLIST are excluded. The default value blacklists CONF_VERSION, BB_NUMBER_THREADS, PARALLEL_MAKE, PRSERV_HOST, and SSTATE_MIRRORS. Variables listed in SDK_LOCAL_CONF_WHITELIST are included. Including a variable in the value of SDK_LOCAL_CONF_WHITELIST overrides either of the above two conditions. The default value is blank. Classes inherited globally with INHERIT that are listed in SDK_INHERIT_BLACKLIST are disabled. Using SDK_INHERIT_BLACKLIST to disable these classes is is the typical method to disable classes that are problematic or unnecessary in the SDK context. The default value blacklists the buildhistory and icecc classes. Additionally, the contents of conf/sdk-extra.conf, when present, are appended to the end of conf/local.conf within the produced SDK, without any filtering. The sdk-extra.conf file is particularly useful if you want to set a variable value just for the SDK and not the OpenEmbedded build system used to create the SDK.

In most cases, the extensible SDK defaults should work. However, some cases exist for which you might consider making adjustments: If your SDK configuration inherits additional classes using the INHERIT variable and you do not need or want those classes enabled in the SDK, you can blacklist them by adding them to the SDK_INHERIT_BLACKLIST variable. The default value of SDK_INHERIT_BLACKLIST is set using the "?=" operator. Consequently, you will need to either set the complete value using "=" or append the value using "_append". If you have classes or recipes that add additional tasks to the standard build flow (i.e. that execute as part of building the recipe as opposed to needing to be called explicitly), then you need to do one of the following: Ensure the tasks are shared state tasks (i.e. their output is saved to and can be restored from the shared state cache), or that the tasks are able to be produced quickly from a task that is a shared state task and add the task name to the value of SDK_RECRDEP_TASKS. Disable the tasks if they are added by a class and you do not need the functionality the class provides in the extensible SDK. To disable the tasks, add the class to SDK_INHERIT_BLACKLIST as previously described. Generally, you want to have a shared state mirror set up so users of the SDK can add additional items to the SDK after installation without needing to build the items from source. See the "Providing Additional Installable Extensible SDK Content" section for information. If you want users of the SDK to be able to easily update the SDK, you need to set the SDK_UPDATE_URL variable. For more information, see the "Providing Updates After Installing the Extensible SDK" section. If you have adjusted the list of files and directories that appear in COREBASE (other than layers that are enabled through bblayers.conf), then you must list these files in COREBASE_FILES so that the files are copied into the SDK. If your OpenEmbedded build system setup uses a different environment setup script other than &OE_INIT_FILE; or oe-init-build-env-memres, then you must set OE_INIT_ENV_SCRIPT to point to the environment setup script you use. You must also reflect this change in the value used for the COREBASE_FILES variable as previously described.

You can change the title shown by the SDK installer by setting the SDK_TITLE variable. By default, this title is derived from DISTRO_NAME when it is set. If the DISTRO_NAME variable is not set, the title is derived from the DISTRO variable.

When you make changes to your configuration or to the metadata and if you want those changes to be reflected in installed SDKs, you need to perform additional steps to make it possible for those that use the SDK to update their installations with the devtool sdk-update command: Arrange to be created a directory that can be shared over HTTP or HTTPS. Set the SDK_UPDATE_URL variable to point to the corresponding HTTP or HTTPS URL. Setting this variable causes any SDK built to default to that URL and thus, the user does not have to pass the URL to the devtool sdk-update command. Build the extensible SDK normally (i.e., use the bitbake -c populate_sdk_ext imagename command). Publish the SDK using the following command: $ oe-publish-sdk some_path/sdk-installer.sh path_to_shared/http_directory You must repeat this step each time you rebuild the SDK with changes that you want to make available through the update mechanism. Completing the above steps allows users of the existing SDKs to simply run devtool sdk-update to retrieve the latest updates. See the "Updating the Extensible SDK" section for further information.

If you want the users of the extensible SDK you are building to be able to add items to the SDK without needing to build the items from source, you need to do a number of things: Ensure the additional items you want the user to be able to install are actually built. You can ensure these items are built a number of different ways: 1) Build them explicitly, perhaps using one or more "meta" recipes that depend on lists of other recipes to keep things tidy, or 2) Build the "world" target and set EXCLUDE_FROM_WORLD_pn-recipename for the recipes you do not want built. See the EXCLUDE_FROM_WORLD variable for additional information. Expose the sstate-cache directory produced by the build. Typically, you expose this directory over HTTP or HTTPS. Set the appropriate configuration so that the produced SDK knows how to find the configuration. The variable you need to set is SSTATE_MIRRORS: SSTATE_MIRRORS = "file://.* http://example.com/some_path/sstate-cache/PATH" You can set the SSTATE_MIRRORS variable in two different places: If the mirror value you are setting is appropriate to be set for both the OpenEmbedded build system that is actually building the SDK and the SDK itself (i.e. the mirror is accessible in both places or it will fail quickly on the OpenEmbedded build system side, and its contents will not interfere with the build), then you can set the variable in your local.conf or custom distro configuration file. You can then "whitelist" the variable through to the SDK by adding the following: SDK_LOCAL_CONF_WHITELIST = "SSTATE_MIRRORS" Alternatively, if you just want to set the SSTATE_MIRRORS variable's value for the SDK alone, create a conf/sdk-extra.conf either in your Build Directory or within any layer and put your SSTATE_MIRRORS setting within that file. This second option is the safest option should you have any doubts as to which method to use when setting SSTATE_MIRRORS.

By default, the extensible SDK bundles the shared state artifacts for everything needed to reconstruct the image for which the SDK was built. This bundling can lead to an SDK installer file that is a Gigabyte or more in size. If the size of this file causes a problem, you can build an SDK that has just enough in it to install and provide access to the devtool command by setting the following in your configuration: SDK_EXT_TYPE = "minimal" Setting SDK_EXT_TYPE to "minimal" produces an SDK installer that is around 35 Mbytes in size, which downloads and installs quickly. You need to realize, though, that the minimal installer does not install any libraries or tools out of the box. These must be installed either "on the fly" or through actions you perform using devtool or explicitly with the devtool sdk-install command. In most cases, when building a minimal SDK you will need to also enable bringing in the information on a wider range of packages produced by the system. This is particularly true so that devtool add is able to effectively map dependencies it discovers in a source tree to the appropriate recipes. Also so that the devtool search command is able to return useful results. To facilitate this wider range of information, you would additionally set the following: SDK_INCLUDE_PKGDATA = "1" See the SDK_INCLUDE_PKGDATA variable for additional information. Setting the SDK_INCLUDE_PKGDATA variable as shown causes the "world" target to be built so that information for all of the recipes included within it are available. Having these recipes available increases build time significantly and increases the size of the SDK installer by 30-80 Mbytes depending on how many recipes are included in your configuration. You can use EXCLUDE_FROM_WORLD_pn-recipename for recipes you want to exclude. However, it is assumed that you would need to be building the "world" target if you want to provide additional items to the SDK. Consequently, building for "world" should not represent undue overhead in most cases. If you set SDK_EXT_TYPE to "minimal", then providing a shared state mirror is mandatory so that items can be installed as needed. See the "Providing Additional Installable Extensible SDK Content" section for more information.