In order to enable legacy search alongside yokozuna, I had to have an `/etc/riak/advanced.config` file with the following contents:

```
[
 {riak_search, [ {enabled, true} ]},
 {merge_index, [
                %% The root dir to store search merge_index data
                {data_root, "/var/lib/riak/merge_index"},

                %% Size, in bytes, of the in-memory buffer.  When this
                %% threshold has been reached the data is transformed
                %% into a segment file which resides on disk.
                {buffer_rollover_size, 1048576},

                %% Overtime the segment files need to be compacted.
                %% This is the maximum number of segments that will be
                %% compacted at once.  A lower value will lead to
                %% quicker but more frequent compactions.
                {max_compact_segments, 20}
               ]}
].
```