If you met error like above picture, change the code in octomap_server_nodelet.cpp like below picture
PLUGINLIB_DECLARE_CLASS(octomap_server, OctomapServerNodelet, octomap_server::OctomapServerNodelet, nodelet::Nodelet);
TO
PLUGINLIB_EXPORT_CLASS(octomap_server::OctomapServerNodelet, nodelet::Nodelet);