From @harlantwood on Fri Jun 17 2016 05:08:47 GMT+0000 (UTC)
Answer: this works well:
IPFS_LOGGING=<level> ipfs daemon
…where is the log level, with ‘debug’ the most verbose and ‘critical’ the least verbose. Possible values of : debug, info, notice, warning, error, critical.
Some more useful discussion here: https://github.com/ipfs/go-ipfs/issues/1816.
Copied from original issue: https://github.com/ipfs/faq/issues/134