I am using Ubuntu 12.10 and have sucessfully installed CUDA 5.0 and its sample kits too. I have also run sudo apt-get install nvidia-cuda-toolkit Below is my hello world program for CUDA:

#include <stdio.h>  /* Core input/output operations                         */
#include <stdlib.h> /* Conversions, random numbers, memory allocation, etc. */
#include <math.h>   /* Common mathematical functions                        */
#include <time.h>   /* Converting between various date/time formats         */
#include <cuda.h>   /* CUDA related stuff                                   */


__global__ void kernel(void) {
}

/* MAIN PROGRAM BEGINS */
int main(void) {

  /* Dg = 1; Db = 1; Ns = 0; S = 0 */
  kernel<<<1,1>>>();

  /* PRINT 'HELLO, WORLD!' TO THE SCREEN */
  printf("\n  Hello, World!\n\n");

  /* INDICATE THE TERMINATION OF THE PROGRAM */
  return 0;
}
/* MAIN PROGRAM ENDS */

The following error occurs when I compile it with nvcc -g hello_world_cuda.cu -o hello_world_cuda.x

/tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `main':
/home/adarshakb/Documents/hello_world_cuda.cu:16: undefined reference to `cudaConfigureCall'
/tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__cudaUnregisterBinaryUtil':
/usr/include/crt/host_runtime.h:172: undefined reference to `__cudaUnregisterFatBinary'
/tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__sti____cudaRegisterAll_51_tmpxft_000033f1_00000000_4_hello_world_cuda_cpp1_ii_b81a68a1':
/tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFatBinary'
/tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFunction'
/tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `cudaError cudaLaunch<char>(char*)':
/usr/lib/nvidia-cuda-toolkit/include/cuda_runtime.h:958: undefined reference to `cudaLaunch'
collect2: ld returned 1 exit status

I am also making sure that I use gcc and g++ version 4.4 ( As 4.7 there is some problem with CUDA)