If you’ve decided that it’s time to upgrade your old Linux Mint 18 “Sarah” installation to the new Linux Mint 18.1 “Serena” release, you can do it right now by opening the Update Manager tool, clicking on the “Refresh” button to check for a new versions of the in-house built mint-upgrade-info and mintupdate utilities. Apply those updates on your Linux Mint 18 OS, then launch the System Upgrade utility by clicking on the “Upgrade to Linux Mint 18.1 Serena” entry under the Edit menu of the Update Manager tool. Follow the instructions displayed on the screen to upgrade your system to Linux Mint 18.1, an operation that should take a few good minutes to finish.