How do I launch px4-sitl in a custom gazebo world

As someone suggested I tried making my_vehcile in both models and world ,model the same as iris and world a custom one I wrote which works(has been tested),and did the sitl_target edit etc all the steps mentioned ,As i run the commands the model and world mentioned in terminal is correct but my gazebo isnt launching it says :NFO [dataman] data manager file ‘./dataman’ size is 7866640 bytes
etc/init.d-posix/rcS: 22: [: Illegal number:
INFO [init] PX4_SIM_HOSTNAME: localhost
INFO [simulator_mavlink] Waiting for simulator to accept connection on TCP port 4560
[Err] [] Failed to connect to master in 30 seconds.
[Err] [] Unable to initialize transport.
[Err] [] Unable to setup Gazebo

looks like the gazebo was not included in the launch file, check the previous world file to see what u missing