Specify client authentication in the properties file like so:

s3proxy.authorization=aws-v4
s3proxy.identity=<access-key>
s3proxy.credential=<secret-key>

Authentication misconfiguration can cause spurious client failures. Ensure that you have NTP enabled on all machines. If all else fails you can disable s3proxy authentication via:

s3proxy.authorization=none

You can use curl to debug s3proxy when authentication is disabled (see above):

• list buckets in a storage account: curl http://<proxy>/
• list blobs in a bucket: curl http://<proxy>/<bucketname>
• add a new bucket: curl -X PUT http://<proxy>/<newbucketname>
• add a new blob to a bucket: curl -X PUT -T <filename> http://<proxy>/<bucketname>/<newblobname>

Debug logging reveals more information about requests:

java -DLOG_LEVEL=debug -jar s3proxy.jar

Trace logging shows the client requests and server responses:

java -DLOG_LEVEL=trace -jar s3proxy.jar

Emit storage backend requests and responses:

java -DLOG_LEVEL=trace -Djclouds.wire=debug -jar s3proxy.jar