Here's what I've found for Bitnami on GCE. The package installs with bitnami:daemon privileges and the webserver runs as daemon.
Part of the typical part of installing an extension is flushing the cache, and when the cache is flushed, jobs on cron recreate the cache, but the cron jobs run as bitnami:bitnami so the ownership of the cache files aren't available to the webserver and magento breaks. This has been verified by a well know extension publisher who recommended to change user for the magento crons to daemon.
If I chown of var/cache back to bitnami:daemon, magento works.
The correct solution is to have the cron run under the same user as the webserver....but daemon can't create a crontab.