BOINC has a feature where it will rotate its log files once they exceed a predefined limit. This won't work under the systemd changes. It used to rename the old stdoutdae.txt to stdoutdae.old and then carry on writing to stdoutdae.txt. If there was an existing old file it would be deleted. The same applies to the stderrdae.txt/old files. You can define a size limit in cc_config.xml. In addition to that BOINC 7.x versions spawn a task to detect GPU presence at startup and these files get created as stderrgpudetect.txt and stdoutgpudetect.txt. They too are getting caught by the systemd changes in Stretch such that the files are present in /var/lib/boinc-client but are zero bytes. BOINC manager and other utilities (I use BOINCtasks) can read the standard stdoutdae.txt to display the content to the user. I believe it does this via an RPC call to the client. BOINCtasks still seems to work. I haven't tried BOINC manager as I don't have X11 installed. The other log files need to be browsed via Terminal.
