Update README.md

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README.md

@@ -47,6 +47,30 @@ Build and Install the Intel(R) SGX Driver
 - Ensure that you have the following required hardware:  
   * 6th Generation Intel(R) Core(TM) Processor or newer
 - Configure the system with the **SGX hardware enabled** option.
+- To build the driver, the version of installed kernel headers must match the active kernel version on the system.
+  * On Ubuntu
+     * To check if matching kernel headers are installed:
+        ```
+        $ dpkg-query -s linux-headers-$(uname -r)
+        ```
+     * To install matching headers:
+        ```
+        $ sudo apt-get install linux-headers-$(uname -r)
+        ```
+  * On CentOS and RHEL
+     * To check if matching kernel headers are installed:
+        ```
+        $ ls /usr/src/kernels/$(uname -r)
+        ``` 
+     * To install matching headers:
+        ```
+        $ sudo yum install kernel-devel
+        ```
+     * After the above command, if the matching headers are still missing in /usr/src/kernels, try update kernel and reboot using commands below. Then choose updated kernel on boot menu.
+        ```
+        $ sudo yum install kernel
+        $ sudo reboot
+        ```
 
 **Note:** Refer to the *"Intel® SGX Resource Enumeration Leaves"* section in the [Intel SGX Programming reference guide](https://software.intel.com/sites/default/files/managed/48/88/329298-002.pdf) to make sure your cpu has the SGX feature.