Usually it's a /major/ update. Like going to a whole new version of libc. If it isn't planned out properly you could end up needing to do a re-install (which

Usually it's a /major/ update. Like going to a whole new version of libc. If it isn't planned out properly you could end up needing to do a re-install (which would be like upgrading from one version of Windows to another; except that generally all of your settings are actually kept as they live in /etc and/or ~/ ). Having said that, I've performed an uncounted greater number of upgrades than I can remember and have only OCCASIONALLY hit this issue, and it was always when I was doing something outside of the distribution recommended set of instructions (more akin to trying to go from WinXP directly to Win10 without any intermediate upgrades).