Tasks can either be a shell task or a Python task.
For shell tasks, BitBake writes a shell script to
${WORKDIR}/temp/run.do_taskname.pid
and then executes the script.
The generated shell script contains all the exported variables, and the shell functions
with all variables expanded.
Output from the shell script goes to the file ${WORKDIR}/temp/log.do_taskname.pid
.
Looking at the expanded shell functions in the run file and the output in the log files
is a useful debugging technique.
For Python tasks, BitBake executes the task internally and logs information to the controlling terminal. Future versions of BitBake will write the functions to files similar to the way shell tasks are handled. Logging will be handled in way similar to shell tasks as well.
Once all the tasks have been completed BitBake exits.
When running a task, BitBake tightly controls the execution environment of the build tasks to make sure unwanted contamination from the build machine cannot influence the build. Consequently, if you do want something to get passed into the build task's environment, you must take a few steps:
Tell BitBake to load what you want from the environment
into the data store.
You can do so through the BB_ENV_EXTRAWHITE
variable.
For example, assume you want to prevent the build system from
accessing your $HOME/.ccache
directory.
The following command tells BitBake to load
CCACHE_DIR
from the environment into the data
store:
export BB_ENV_EXTRAWHITE="$BB_ENV_EXTRAWHITE CCACHE_DIR"
Tell BitBake to export what you have loaded into the
environment store to the task environment of every running task.
Loading something from the environment into the data store
(previous step) only makes it available in the datastore.
To export it to the task environment of every running task,
use a command similar to the following in your
local.conf
or distro configuration file:
export CCACHE_DIR
BB_HASHBASE_WHITELIST
example in the "Checksums (Signatures)" section.