%poky; ] > Features provide a mechanism for working out which packages should be included in the generated images. Distributions can select which features they want to support through the DISTRO_FEATURES variable, which is set in the poky.conf distribution configuration file. Machine features are set in the MACHINE_FEATURES variable, which is set in the machine configuration file and specifies the hardware features for a given machine. These two variables combine to work out which kernel modules, utilities, and other packages to include. A given distribution can support a selected subset of features so some machine features might not be included if the distribution itself does not support them.

The items below are valid options for DISTRO_FEATURES: alsa: ALSA support will be included (OSS compatibility kernel modules will be installed if available). bluetooth: Include bluetooth support (integrated BT only) ext2: Include tools for supporting for devices with internal HDD/Microdrive for storing files (instead of Flash only devices) irda: Include Irda support keyboard: Include keyboard support (e.g. keymaps will be loaded during boot). pci: Include PCI bus support pcmcia: Include PCMCIA/CompactFlash support usbgadget: USB Gadget Device support (for USB networking/serial/storage) usbhost: USB Host support (allows to connect external keyboard, mouse, storage, network etc) wifi: WiFi support (integrated only) cramfs: CramFS support ipsec: IPSec support ipv6: IPv6 support nfs: NFS client support (for mounting NFS exports on device) ppp: PPP dialup support smbfs: SMB networks client support (for mounting Samba/Microsoft Windows shares on device)

The items below are valid options for MACHINE_FEATURES: acpi: Hardware has ACPI (x86/x86_64 only) alsa: Hardware has ALSA audio drivers apm: Hardware uses APM (or APM emulation) bluetooth: Hardware has integrated BT ext2: Hardware HDD or Microdrive irda: Hardware has Irda support keyboard: Hardware has a keyboard pci: Hardware has a PCI bus pcmcia: Hardware has PCMCIA or CompactFlash sockets screen: Hardware has a screen serial: Hardware has serial support (usually RS232) touchscreen: Hardware has a touchscreen usbgadget: Hardware is USB gadget device capable usbhost: Hardware is USB Host capable wifi: Hardware has integrated WiFi

The contents of images generated by the OpenEmbedded build system can be controlled by the IMAGE_FEATURES and EXTRA_IMAGE_FEATURES variables that you typically configure in your image recipes. Through these variables you can add several different predefined packages such as development utilities or packages with debug information needed to investigate application problems or profile applications. Current list of IMAGE_FEATURES contains the following: splash: Enables showing a splash screen during boot. By default, this screen is provided by psplash, which does allow customization. If you prefer to use an alternative splash screen package, you can do so by setting the SPLASH variable to a different package name (or names) within the image recipe or at the distro configuration level. ssh-server-dropbear: Installs the Dropbear minimal SSH server. ssh-server-openssh: Installs the OpenSSH SSH server, which is more full-featured than Dropbear. Note that if both the OpenSSH SSH server and the Dropbear minimal SSH server are present in IMAGE_FEATURES, then OpenSSH will take precedence and Dropbear will not be installed. x11: Installs the X server x11-base: Installs the X server with a minimal environment. x11-sato: Installs the OpenedHand Sato environment. tools-sdk: Installs a full SDK that runs on the device. tools-debug: Installs debugging tools such as strace and gdb. tools-profile: Installs profiling tools such as oprofile, exmap, and LTTng. tools-testapps: Installs device testing tools (e.g. touchscreen debugging). nfs-server: Installs an NFS server. dev-pkgs: Installs development packages (headers and extra library links) for all packages installed in a given image. staticdev-pkgs: Installs static development packages (i.e. static libraries containing *.a files) for all packages installed in a given image. dbg-pkgs: Installs debug symbol packages for all packages installed in a given image. doc-pkgs: Installs documentation packages for all packages installed in a given image.

Sometimes, it is necessary for a new feature to be added to control existing functionality that was previously enabled by default and not able to be disabled. In order to ensure that the feature remains enabled for users with existing configurations that upgrade to a new version of the core metadata without that configuration having to be changed, while still allowing others who want to turn the feature off to do so, the backfilling mechanism was introduced. This functionality is available for DISTRO_FEATURES and MACHINE_FEATURES. An example is the "pulseaudio" distro feature. Previously, PulseAudio support was enabled within the Qt and GStreamer frameworks. However some users desired to be able to disable this. To allow this to be disabled without affecting existing configurations in which PulseAudio support should remain enabled, "pulseaudio" was added to DISTRO_FEATURES_BACKFILL within meta/conf/bitbake.conf. This means that "pulseaudio" is automatically added to DISTRO_FEATURES without the distro configuration needing to be updated to do so itself. Those who do not want PulseAudio support can add "pulseaudio" to DISTRO_FEATURES_BACKFILL_CONSIDERED in their distro .conf file and this will disable adding "pulseaudio" to DISTRO_FEATURES. Another example is the "rtc" machine feature. Previously, real time clock (RTC) support was enabled for all target devices. However certain targets do not have this capability. To allow this to be disabled by such machines without affecting other machines in which RTC support should remain enabled, "rtc" was added to MACHINE_FEATURES_BACKFILL within meta/conf/bitbake.conf. This means that "rtc" is automatically added to MACHINE_FEATURES without the machine configuration needing to be updated to do so itself. For machines that not need RTC support can add "rtc" to MACHINE_FEATURES_BACKFILL_CONSIDERED in their machine .conf file and this will disable adding "rtc" to MACHINE_FEATURES.