$ minetestserver --config ~/minetest/minetest.conf --world ~/minetest/world.mt
2017-05-11 17:57:31: WARNING[Main]: system-wide share not found at "/usr/share/minetest"
2017-05-11 17:57:31: WARNING[Main]: system-wide share not found at "/usr/bin/../share/minetest"
2017-05-11 17:57:31: WARNING[Main]: system-wide share not found at "/usr/bin/.."
2017-05-11 17:57:31: WARNING[Main]: Couldn't find a locale directory!
2017-05-11 17:57:31: [Main]: Supplied world.mt file - stripping it off.
2017-05-11 17:57:31: ERROR[Main]: Subgame specified in default_game [minetest] is invalid.
2017-05-11 17:57:31: ERROR[Main]: ServerError: Supplied invalid gamespec