Starting Aug 4, 2016, systems using an interim HWE Stack older than the Xenial HWE Stack will no longer receive software and security updates for the kernel and, if you're running it, the graphics stack.
Further details here:
If you are using Ubuntu 14.04.2 - 14.04.5, or one of their derivatives, either log into a terminal session (e.g. Ctrl + Alt + F1) or run this command in a terminal emulator:
hwe-support-status --verbose... and see if you get this message:
WARNING: Security updates for your current Hardware Enablement Stack ended on 2016-08-04: * http://wiki.ubuntu.com/1404_HWE_EOL To upgrade to a supported (or longer-supported) configuration: * Upgrade from Ubuntu 14.04 LTS to Ubuntu 16.04 LTS by running: sudo do-release-upgrade OR * Switch to the current security-supported stack by running: sudo apt-get install libwayland-egl1-mesa-lts-xenial xserver-xorg-lts-xenial linux-image-generic-lts-xenial libgl1-mesa-glx-lts-xenial linux-generic-lts-xenial and reboot your system.Following the advice above will upgrade the Hardware Enablement Stack to 16.04, and the rest of the distro will be 14.04.5.
Alternatively, install *buntu 14.04.1, which doesn't have a Hardware Enablement Stack and is supported until 2019. When you update *buntu 14.04.1, it stays at 14.04.1.
Edited by Al1000, 02 September 2016 - 10:48 AM.