Note : Domain ID or domid is only for Running VMs or Booting VMs. ( A VM which is powered off will not have a domid of its own )  

Run the following command to obtain the domain ID of a particular VM running on XenServer.

# xl list | grep -i "VM_NAME" 


OR

# list_domains | grep -i VM_UUID



In the above case , the domain ID is 2 for the Virtual Machine - Citrix WLB Virtual Appliance

(To find the UUID of the VM , Click on the VM > Click on General Tab > Right click On UUID > copy the UUID to clipboard > Now you can paste the same while executing the command - list_domains | grep -i UUID_Of_THE_VM )