If you have a RabbitMQ cluster and a crashed node fails to start again with 
{"init terminating in do_boot",{undef,[{rabbit_prelaunch,start,[]},{init,start_it,1},{init,start_em,1}]}}
in /var/log/rabbitmq/startup_log and something like 
Error description:
   {could_not_start,rabbitmq_management,
       {{shutdown,
            {failed_to_start_child,rabbit_mgmt_sup,
                {'EXIT',
                    {{shutdown,
                         [{{already_started,<9180.461.0>},
                           {child,undefined,rabbit_mgmt_db,
                               {rabbit_mgmt_db,start_link,[]},
                               permanent,4294967295,worker,
                               [rabbit_mgmt_db]}}]},
                     {gen_server2,call,
                         [<0.427.0>,{init,<0.425.0>},infinity]}}}}},
        {rabbit_mgmt_app,start,[normal,[]]}}}

Log files (may contain more information):
   /var/log/rabbitmq/[email protected]
   /var/log/rabbitmq/[email protected]
in /var/log/rabbitmq/[email protected] then you might want to try to drop the node from the cluster by running 
rabbitmqctl forget_cluster_node [email protected]
one a working cluster node and rejoin the node by running 
rabbitmqctl join_cluster [email protected]
on the disconnected node (given rabbit-02 is a working cluster member). Note: Doing this might make you lose messages!