$ curl -d '{ "jsonrpc": "2.0", "id": 1, "method": "call", "params": [ "00000000000000000000000000000000", "session", "login", { "username": "root", "password": "secret"  } ] }'  http://10.11.12.13/ubus
{"jsonrpc":"2.0","id":1,"result":[0,{"ubus_rpc_session":"2d4cd44e609baf09f43c7b0928dcd840",/*...*/}]}