I already had geth installed and Rinkeby testnet synced. After that, I wanted to see how Mist works and downloaded Mist ( 36.7 MB Mist-linux64-0-9-0.deb).
When launched Mist and choose Rinkeby test net, synchronization started again from block 0. Could there have been a way for me to use already downloaded blockchain with geth.
Secondary questions: Also, if I install Mist, do I need to install Ethereum Wallet also? Is it already included with Mist? If geth is included in Mist, but I had geth installed previously, could that be a problem in future?