Upgrade SCCM 2012 SP1 to SCCM 2012 R2 steps

This guide explains how to upgrade SCCM 2012 SP1 to SCCM 2012 R2.
Preparing for Upgrade:
1. Restart the Primary site server
2. Review the site status and resolve any errors
3. Backup, backup and Backup the existing SCCM database
4. Copy the copy of the database to some other network location

Upgrade Tasks:
1. Upgrade ADK to Windows ADK 8.1
2. Upgrade SCCM 2012 SP1 to SCCM 2012 R2
3. Install CU levels
4. Upgrade SCCM 2012 SP1 secondary site server to SCCM R2
5. Upgrade the consoles