powerd writes logs to the /var/log/power_manager directory. It creates a new file every time it starts and updates powerd.LATEST and powerd.PREVIOUS symlinks to point to the current and previous files.
Any output written to stdout or stderr (including messages that are printed before the logging library has been initialized) are redirected to /var/log/powerd.out.
Output from the powerd_suspend script, along with suspend- and resume-related kernel messages, are written to /var/log/messages.
powerd receives input (e.g. user/video/audio activity, lid events, etc.) and performs actions sporadically; thirty-second intervals where nothing happens are common for an idle system. Having logs of these events is essential to reconstruct the past when investigating user feedback reports.
powerd's unit tests, on the other hand, send a bunch of input very quickly. Logging all events drowns out the rest of the testing output.
To produce useful output when running in production while producing readable output from tests, powerd logs messages at the INFO level and above by default, while unit tests log WARNING and above.
Please use logging macros as follows within powerd:
| Macro | Usage |
|---|---|
VLOG(1) | Debugging info that is hidden by default but can be selectively enabled by developers |
LOG(INFO) | Input from other systems or actions performed by powerd (i.e. things that would be useful when trying to figure out what powerd was thinking when investigating a bug report) |
LOG(WARNING) | Minor errors (e.g. bad input from other daemons) |
LOG(ERROR) | Major errors (e.g. problems communicating with the kernel) |
LOG(FATAL) | Critical problems that make powerd unusable or that indicate problems in the readonly system image (e.g. malformed preference defaults) |
CHECK(...) | Same as LOG(FATAL) |