[Koha] First catalog, first search failed

MyLibrary-intra.example.net Once I've defined a (I hope) final framework to work with, I've catalogued a first book. I didn't add any "item". Just after this, I've visited OPAC at ~ MyLibrary.example.net and filled search textbox with author's name -> [Go] The answer is: You did not specify any search criteria No results found! You did not specify any search criteria. Error: Could not find opac-search.xml in /usr/share/koha/opac/cgi-bin/opac/ at /usr/share/koha/lib/C4/Search.pm line 871. What have I missed to do for this Koha 17.11 setup? Thanks.