2.8.6. Images

The images produced by the OpenEmbedded build system are compressed forms of the root filesystem that are ready to boot on a target device. You can see from the general Yocto Project Development Environment figure that BitBake output, in part, consists of images. This section is going to look more closely at this output:

For a list of example images that the Yocto Project provides, see the "Images" chapter in the Yocto Project Reference Manual.

Images are written out to the Build Directory inside the tmp/deploy/images/machine/ folder as shown in the figure. This folder contains any files expected to be loaded on the target device. The DEPLOY_DIR variable points to the deploy directory, while the DEPLOY_DIR_IMAGE variable points to the appropriate directory containing images for the current configuration.

kernel-image: A kernel binary file. The KERNEL_IMAGETYPE variable setting determines the naming scheme for the kernel image file. Depending on that variable, the file could begin with a variety of naming strings. The deploy/images/machine directory can contain multiple image files for the machine.
root-filesystem-image: Root filesystems for the target device (e.g. *.ext3 or *.bz2 files). The IMAGE_FSTYPES variable setting determines the root filesystem image type. The deploy/images/machine directory can contain multiple root filesystems for the machine.
kernel-modules: Tarballs that contain all the modules built for the kernel. Kernel module tarballs exist for legacy purposes and can be suppressed by setting the MODULE_TARBALL_DEPLOY variable to "0". The deploy/images/machine directory can contain multiple kernel module tarballs for the machine.
bootloaders: Bootloaders supporting the image, if applicable to the target machine. The deploy/images/machine directory can contain multiple bootloaders for the machine.
symlinks: The deploy/images/machine folder contains a symbolic link that points to the most recently built file for each machine. These links might be useful for external scripts that need to obtain the latest version of each file.