Linux Mint 18.2 was released just a couple of days ago, and already the development team have enabled the upgrade path for users running Linux Mint 18 or Linux Mint 18.1; this is quite surprising as it has usually taken a week or so, in the past, to switch on upgrades.
Upgrading to Linux Mint 18.2 from 18.1, or 18, will leave several parts of the old release in tact, for example, MDM remains the login manager instead of switching to LightDM, and the Linux Kernel will remain on version 4.4 instead of being bumped to 4.8, this is to ensure system stability; by upgrading though, you’ll receive an update to your desktop environment and all of the software written by the Linux Mint team. The upgrade should take mere minutes to finish even on a basic internet connection.
To upgrade you need to head over to the Update Manager and hit the refresh button to pull up the latest update, keep applying the updates until it no longer offers mintupdate or mint-upgrade-info. Now that those updates are done, the Mint Update tool should refresh, and you can now go to Edit in the menu and find an option to Upgrade to “Linux Mint 18.2 Sonya”.
The upgrade dialog box will open up, and run you through several slides (Intro, Release Notes, New Features, Requirements, Summary), once you agree to the update, it should finish in a fairly short space of time. Once complete, reboot the system.
As mentioned earlier, the Linux Kernel and the LightDM login manager won’t be included in the update, these have to be installed manually, or you can opt for a clean install of Linux Mint 18.2. If you opt to leave these two items as they are, your system will continue to operate normally; if you’re a novice user, messing with either the login manager or Linux Kernel may break your system and make it difficult to repair, so they’re best left alone.
If you are running an earlier release of Linux Mint 18.x and you're happy with the system, then you needn't worry, you’ll still receive security updates to the software as usual until 2021.
Source: Linux Mint