add notes on log files

Change-Id: Ifbd5d2cd9d7ab5916fa06f903e1b4386a96db3fc
diff --git a/PLATFORM_INSTALL_INTERNALS.md b/PLATFORM_INSTALL_INTERNALS.md
index f38b82e..1a21924 100644
--- a/PLATFORM_INSTALL_INTERNALS.md
+++ b/PLATFORM_INSTALL_INTERNALS.md
@@ -80,4 +80,8 @@
 
 The final ansible role executed by platform-install is to start XOS. This uses the XOS `service-profile` repository to bring up a stack of CORD services. 
 
-For a discussion of how the XOS service-profile system works, please see [Dynamic On-boarding System and Service Profiles](https://wiki.opencord.org/display/CORD/Dynamic+On-boarding+System+and+Service+Profiles). 
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+For a discussion of how the XOS service-profile system works, please see [Dynamic On-boarding System and Service Profiles](https://wiki.opencord.org/display/CORD/Dynamic+On-boarding+System+and+Service+Profiles). 
+
+## Helpful log files and diagnostic information
+
+The xos-build and xos-onboard steps run ansible playbooks to setup the xos virtual machine. The output of these playbooks is stored in the files `service-profile/cord-pod/xos-build.out` and `service-profile/cord-pod/xos-onboard.out` respectively. 
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