Ubuntu 16.04 LTS features in the latest Windows 10 Insider Preview (build 14936).
When enabling the ‘Bash on Ubuntu on Windows’ feature for the first time Windows 10 now installs an Ubuntu 16.04 (Xenial Xerus) image instead of Ubuntu 14.04 (Trusty Tahr).
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
Get Windows 10 Build 14936
Windows 10 Preview Build 14936 is only available to Windows insiders who are in the fast-ring.
If you are not currently part of the Windows 10 Insider program, but want to be, visit the official Insider webpage from a Windows machine to get more information on joining.
To get the update (assuming you’re eligible) head to Settings > Update and recovery > Preview builds and click the ‘Check Now’ button.
Source : omgubuntu