: SimplePostTool: FATAL: Solr returned an error: : Unexpected_character_m_code_109_in_prolog_expected___at_rowcol_unknownsource_11
if you look at your solr log (or the HTTP response body, SimplePostTool only gives you the status line) you'll see the more human readable form of that error which is probably something like... Unexpected character 'm' (code 109) in prolog; expected '<' at [row,col {unknown-source}]: [1,1] in short: this has nothing to do with the fact that you are running multi-core, and everything to do with the fact that one of your xml files isn't valid XML and has an "m" in the first character of the first line. (it is most likely one of the XML files you are trying to post .. but there is a remote possibility it is in one of your config files -- i can't remember if config parsing errors are saved to use as HTTP errors in this way, but since you didn't confirm wehter you could actually load things like the admin screen after starting solr, i'm not sure off the top of my head) -Hoss