What Do All The Build Output Files Do?

A Yocto build normally generated a confusing amount of files in the output build directory. This section aims to help you work out what all these files do!

Note that only important files are listed here, and some may be symlinks to the actual file (the symlink is listed below instead of the destination file because it’s file name is easier to read and understand).

Example files are colored as they would appear with the ls command under Ubuntu. Normal files are in white. Symlinks are in light blue. Listed in alphabetical order.

Filename: boot.bin
Description: FSBL file. This is a machine/date independent symlink to the actual FSBL file in the same directory.
Example: boot.bin
Example File Size: 89kiB (destination of symlink)

Filename: <image-name>-<machine>-<date-time>.rootfs.cpio
Description: The root filesystem, in the copy-in copy-out (cpio) archive format. Also called a ramdisk.
Example: core-image-minimal-zc702-zynq7-20170531002052.rootfs.cpio
Example File Size: 315MiB

Filename: <image-name>-<machine>-<date-time>.rootfs.cpio.gz.u-boot
Description: The root filesystem, with a U-boot header added to that U-boot can boot it. Also called a ramdisk.
Example: core-image-minimal-zc702-zynq7-20170531002052.rootfs.cpio.gz.u-boot 
Example File Size: 103MiB

Filename: <image-name>-<machine>-<date-time>.rootfs.manifest
Description: Contains a list of all the packages present in the image.
Example: core-image-minimal-

Example File Size: 43kiB

Filename: <image-name>-<machine>-<date-time>.rootfs.tar.gz
Description: The root filesystem, as a tar archive that has also been compressed with gz.
Example: core-image-minimal-

Example File Size: 103MiB

Filename: uImage
Description: An image of the kernal, wrapped with a U-Boot header. This is a date/machine independent symlink to the actual image file in the same directory.
Example: uImage
Example File Size: 3.5MiB (symlink destination)

Filename: uImage-<machine>.dtb
Description: This is the Devicetree blob in binary format. This is a kernel/date independent symlink to the actual Devicetree file in the same directory. You can convert this to a .dts file (human-readable Devicetree file) using the dtc program.
Example: uImage-zynq-zc702.dtb
Example File Size: 15kiB (symlink destination)