I am having the same issue, and it appears to be specific to the 1.12 jar. I am using a couple of servers that have been through every version since 1.7.2, and never had a problem. Now, I can run them with any of the 1.11.X jars, but if I select the 1.12 jar, nothing occurs and nothing shows up in the server log. I tried this with a brand new, from scratch, server, and it won’t start with 1.12 either. Below is my mineos.log, the first two lines are from a server (Creative_Vanilla) that has been running 1.11.2, and the remaining lines (Test112) are from a brand new server. This is with git commit d3eb568, node.js. Running the reset_webui.sh script didn’t change the symptoms.
9213 {"level":"info","message":"[Creative_Vanilla] 192.168.5.29 issued command : \"start\"","timestamp":"2017-06-09T03:58:53.568Z"}
9214 {"level":"info","message":"[Creative_Vanilla] received request \"start\"","timestamp":"2017-06-09T03:58:53.569Z"}
9215 {"command":"create","server_name":"test112","properties":{"generate-structures":true,"server-port":"25588","difficulty":"3","gamemode":"0","enable-query":true},"level":"info","message":"[WEBUI] Received emit command from 192.168.5.29:mc","timestamp":"2017-06-09T04:04:03.217Z"}
9216 {"level":"info","message":"[test112] Discovered server","timestamp":"2017-06-09T04:04:03.269Z"}
9217 {"level":"error","message":"[test112] Create tail on logs/latest.log failed","timestamp":"2017-06-09T04:04:03.270Z"}
9218 {"level":"info","message":"[test112] Watching for file generation: logs/latest.log","timestamp":"2017-06-09T04:04:03.270Z"}
9219 {"level":"error","message":"[test112] Create tail on server.log failed","timestamp":"2017-06-09T04:04:03.272Z"}
9220 {"level":"info","message":"[test112] Watching for file generation: server.log","timestamp":"2017-06-09T04:04:03.272Z"}
9221 {"level":"error","message":"[test112] Create tail on proxy.log.0 failed","timestamp":"2017-06-09T04:04:03.273Z"}
9222 {"level":"info","message":"[test112] Watching for file generation: proxy.log.0","timestamp":"2017-06-09T04:04:03.273Z"}
9223 {"level":"error","message":"[test112] Create tail on logs/fml-server-latest.log failed","timestamp":"2017-06-09T04:04:03.274Z"}
9224 {"level":"info","message":"[test112] Watching for file generation: logs/fml-server-latest.log","timestamp":"2017-06-09T04:04:03.274Z"}
9225 {"level":"info","message":"[test112] Using skipDirEntryPatterns: world,world_the_end,world_nether,dynmap,plugins,web,logs,region,playerdata,stats,data","timestamp":"2017-06-09T04:04:03.275Z"}
9226 {"level":"info","message":"[test112] Server created in filesystem.","timestamp":"2017-06-09T04:04:03.325Z"}
9227 {"level":"info","message":"[test112] mc (192.168.5.29) joined server namespace","timestamp":"2017-06-09T04:04:03.358Z"}
9228 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"modify_sc\"","timestamp":"2017-06-09T04:04:03.367Z"}
9229 {"level":"info","message":"[test112] received request \"modify_sc\"","timestamp":"2017-06-09T04:04:03.369Z"}
9230 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"modify_sc\"","timestamp":"2017-06-09T04:04:14.057Z"}
9231 {"level":"info","message":"[test112] received request \"modify_sc\"","timestamp":"2017-06-09T04:04:14.059Z"}
9232 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"modify_sc\"","timestamp":"2017-06-09T04:04:18.193Z"}
9233 {"level":"info","message":"[test112] received request \"modify_sc\"","timestamp":"2017-06-09T04:04:18.194Z"}
9234 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"modify_sc\"","timestamp":"2017-06-09T04:04:23.167Z"}
9235 {"level":"info","message":"[test112] received request \"modify_sc\"","timestamp":"2017-06-09T04:04:23.167Z"}
9236 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"accept_eula\"","timestamp":"2017-06-09T04:04:28.076Z"}
9237 {"level":"info","message":"[test112] received request \"accept_eula\"","timestamp":"2017-06-09T04:04:28.076Z"}
9238 {"level":"info","message":"[test112] eula.txt detected: ACCEPTED (eula=true)","timestamp":"2017-06-09T04:04:28.605Z"}
9239 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"start\"","timestamp":"2017-06-09T04:04:29.956Z"}
9240 {"level":"info","message":"[test112] received request \"start\"","timestamp":"2017-06-09T04:04:29.957Z"}
9241 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"start\"","timestamp":"2017-06-09T04:04:37.806Z"}
9242 {"level":"info","message":"[test112] received request \"start\"","timestamp":"2017-06-09T04:04:37.806Z"}
9243 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"start\"","timestamp":"2017-06-09T04:05:02.871Z"}
9244 {"level":"info","message":"[test112] received request \"start\"","timestamp":"2017-06-09T04:05:02.874Z"}
9245 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"copy_profile\"","timestamp":"2017-06-09T04:05:04.209Z"}
9246 {"level":"info","message":"[test112] received request \"copy_profile\"","timestamp":"2017-06-09T04:05:04.210Z"}
9247 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"start\"","timestamp":"2017-06-09T04:05:15.607Z"}
9248 {"level":"info","message":"[test112] received request \"start\"","timestamp":"2017-06-09T04:05:15.608Z"}
9249 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"start\"","timestamp":"2017-06-09T04:05:26.021Z"}
9250 {"level":"info","message":"[test112] received request \"start\"","timestamp":"2017-06-09T04:05:26.024Z"}
9251 {"level":"info","message":"[test112] 192.168.5.29 issued command : \"start\"","timestamp":"2017-06-09T04:05:28.174Z"}
9252 {"level":"info","message":"[test112] received request \"start\"","timestamp":"2017-06-09T04:05:28.175Z"}