The service packaged with SymmetricDS is using the x86 32-bit version of Java Service Wrapper. You'll want to download the latest version of JSW for your platform, which is Linux x86 64-bit community edition found here:
http://wrapper.tanukisoftware.com/doc/english/download.jsp
Then copy the files into place:
jsw/bin/wrapper -> symmetricds/bin/sym_service
jsw/lib/wrapper.jar -> symmetricds/lib/wrapper.jar
jsw/lib/libwrapper.so -> symmetricds/lib/libwrapper.so