As a reminder, Raspberry Pi 2 is a credit card-sized ARM singleboard computer, ideal for creating DIY (Do It Yourself) project or learning programming and electronics.
Recently, Canonical has announced that they have updated the version of Kernel 4.2 used on Ubuntu 15.10 for Raspberry Pi 2. It fixes a ptrace issue with user namespaces in the Kernel and brings a bunch of fixes as well.
In order to get the latest Kernel on your Ubuntu 15.10 Wily Werewolf system running on Raspberry Pi 2, just perform a regular system upgrade:
$ sudo apt-get update
$ sudo apt-get dist-upgrade
After the upgrade process finishes, reboot the system:
$ sudo reboot