artd is a component of ART Service. It is a shim service to do tasks that require elevated permissions that are not available to system_server, such as manipulation of the file system and invoking dex2oat. It publishes a binder interface that is internal to ART service's Java code. When it invokes other binaries, it passes input and output files as FDs and drops capability before exec.
artd can be controlled by the system properties listed below. Note that the list doesn't include options passed to dex2oat and other processes.
dalvik.vm.artd-verbose: Log verbosity of the artd process. The syntax is the same as the runtime's -verbose flag.