I have Linux node which has SCOM agent installed.I want to know how to find its management group for SCOM and how can I remove or add new management group to that node.
This is invalid question. There is no linux/Unix server used as SCOM server. SCOM is Windows application. You can only monitor the linux/unix servers/nodes under SCOM there no relation with management group and the linux machine. As management group is assigned to Windows management server at a time of SCOM installation. That management server falls into a particular management group. There is no relation with Linux/unix machine as its always related to windows server only.