$ rosrun gazebo_ros spawn_model -h
usage: spawn_model [-h] (-urdf | -sdf)
                   (-file FILE_NAME | -param PARAM_NAME | -database MODEL_NAME | -stdin)
                   -model MODEL_NAME [-reference_frame REFERENCE_FRAME]
                   [-gazebo_namespace GAZEBO_NAMESPACE]
                   [-robot_namespace ROBOT_NAMESPACE] [-unpause]
                   [-wait MODEL_NAME] [-x X] [-y Y] [-z Z] [-R R] [-P P]
                   [-Y Y] [-J JOINT_NAME JOINT_POSITION] [-package_to_model]
                   [-b]

Spawn a model in gazebo using the ROS API

optional arguments:
  -h, --help            show this help message and exit
  -urdf                 Incoming xml is in urdf format
  -sdf                  Incoming xml is in sdf format
  -file FILE_NAME       Load model xml from file
  -param PARAM_NAME     Load model xml from ROS parameter
  -database MODEL_NAME  Load model XML from specified model in Gazebo Model
                        Database
  -stdin                Load model from stdin
  -model MODEL_NAME     Name of model to spawn
  -reference_frame REFERENCE_FRAME
                        Name of the model/body where initial pose is defined.
                        If left empty or specified as "world", gazebo world
                        frame is used
  -gazebo_namespace GAZEBO_NAMESPACE
                        ROS namespace of gazebo offered ROS interfaces.
                        Defaults to /gazebo/
  -robot_namespace ROBOT_NAMESPACE
                        change ROS namespace of gazebo-plugins
  -unpause              !!!Experimental!!! unpause physics after spawning
                        model
  -wait MODEL_NAME      !!!Experimental!!! wait for model to exist
  -x X                  x component of initial position, meters
  -y Y                  y component of initial position, meters
  -z Z                  z component of initial position, meters
  -R R                  roll angle of initial orientation, radians
  -P P                  pitch angle of initial orientation, radians
  -Y Y                  yaw angle of initial orientation, radians
  -J JOINT_NAME JOINT_POSITION
                        initialize the specified joint at the specified
                        position
  -package_to_model     convert urdf <mesh filename="package://..." to <mesh
                        filename="model://..."
  -b                    bond to gazebo and delete the model when this program
                        is interrupted