As you are using Linux based System while specifying the absolute path of the GeckoDriver you have to trim the extension part i.e. .exe
part as follows :
System.setProperty("webdriver.gecko.driver", "/root/Desktop/jarselenium/geckodriver");
Update
As you are still seeing the error ensure that :
- GeckoDriver is present in the specified location.
- GeckoDriver is having executable permission for non-root users. (chmod 777)
- Execute your
@Test
as a non-root user.