When Building a Mender Yocto Project image for your own project and device, you encounter a build error similar to the following:
ERROR: Multiple .bb files are due to be built which each provide u-boot (.../tisdk/sources/meta-variscite/recipes-bsp/u-boot/u-boot-var-som-am33.bb .../tisdk/sources/meta-ti/recipes-bsp/u-boot/u-boot_2014.07.bb). This usually means one provides something the other doesn't and should.
Mender needs to configure U-Boot in order to support robust rootfs rollback. If your project relies on a fork of U-Boot this needs to be integrated. For more information, see Integrating with U-Boot, in particular the section on Forks of U-boot.
Sometimes it happens that U-Boot will refer to a storage device as
mmc 0, whereas the Linux kernel will refer to the same device as
/dev/mmcblk1 (note the different index). In this case the Mender build system must be told explicitly about this disagreement. To do so, you can set the following two variables:
MENDER_UBOOT_STORAGE_INTERFACE = "mmc" MENDER_UBOOT_STORAGE_DEVICE = "0"
which will set the index that U-Boot will use. All non-U-Boot references to the storage device, including the
root argument passed by U-Boot to the Linux kernel when booting it, will keep using the
/dev/mmcblk1 variant derived from
By default Mender does not add any boot loader files to the boot partition. If your device requires this you need to specify the files in the
IMAGE_BOOT_FILES variable in the
machine.conf file for your device. For example:
IMAGE_BOOT_FILES ?= "u-boot.bin MLO"
See the Yocto Project documentation for more information about the
In order to support robust rootfs rollback, Mender depends on being able to tell the bootloader to roll back to the known-working rootfs if attempts to boot the updated rootfs fails a given number of times. Currently, Mender uses the Boot Count Limit feature of U-Boot to achieve this. If you see errors similar to the following during the Yocto Project build process, the U-Boot you are using most likely does not support this feature.
include/config_mender.h:34:3: error: #error CONFIG_BOOTCOUNT_ENV is required for Mender to work
There are two alternatives to resolve this issue. Either you can upgrade to U-Boot v2014.07 or newer, where Boot Count Limit was introduced, or you can patch your current U-Boot version to support this or a similar feature. Please see Bootloader support for more information.