'The latest Windows 10 Insider preview -- build 14936 -- features Ubuntu 16.04 LTS. When a user enables the 'Bash on Ubuntu on Windows' feature for the first time, OMGUbuntu reports, Windows 10 now installs an Ubuntu 16.04 (Xenial Xerus) image instead of Ubuntu 14.04 (Trusty Tahr). From the report:

The updated version of Ubuntu in the WSL only affects new instances, i.e., those created by running lxrun.exe /install or on the very first run of the bash.exe setup. It is possible to upgrade WSL instances from Ubuntu 14.04 to Ubuntu 16.04 manually by running the do-release-upgrade command. Other changes in the WSL in Build 14936 include support for chroot system call, epoll support for /dev/null and the ability for bash -c to redirect to a file.'

-- source: https://linux.slashdot.org/story/16/10/03/198222

Cheers, Peter