Tips

• Overwriting Yocto Classes through meta-layer

To control additional or user defined recipe's variables from env (usefull for CI) add variables to BB_ENV_PASSTHROUGH_ADDITIONS:

export foo="BAR"
export BB_ENV_PASSTHROUGH_ADDITIONS="${BB_ENV_PASSTHROUGH_ADDITIONS} foo BUILD_VERSION CI_COMMIT_BRANCH CI_COMMIT_SHORT_SHA"
bitbake ...

IMAGE_PREPROCESS_COMMAND += “rsync -a –exclude=.git ${FILE_SRC}/rootfs/* ${WORKDIR}/rootfs;”

No override or appends mechanism. But some workaround possible:

1. override variables in local.conf
2. create new conf file and inherit old one with require
3. create new conf file with the same name to mask old file (take care of layer priority)

When creatung new machine.conf based on existing one MACHINEOVERRIDES can be used:

machine-overrides-extender.bbclass

inherit logging
 
bb.debug("HELLO = %s" % HELLO)