Windows Bash (WSL) - sudo: no tty present and no askpass program specified

So silly, after looking further down I see a solution from Beorat:

To avoid the sudo tty issue and others, run these commands just before running do-release-upgrade:

sudo -S apt-mark hold sudosudo -S apt-mark hold procpssudo -S apt-mark hold strace

If you've already upgraded, run the above commands, then manually downgrade to the Trusty packages:

sudo -S wget http://mirrors.kernel.org/ubuntu/pool/main/s/sudo/sudo_1.8.9p5-1ubuntu1.1_amd64.debsudo -S wget http://mirrors.kernel.org/ubuntu/pool/main/p/procps/procps_3.3.9-1ubuntu2_amd64.debsudo -S wget http://mirrors.kernel.org/ubuntu/pool/main/s/strace/strace_4.8-1ubuntu5_amd64.debsudo -S dpkg -i sudo_1.8.9p5-1ubuntu1.1_amd64.debsudo -S dpkg -i procps_3.3.9-1ubuntu2_amd64.debsudo -S dpkg -i strace_4.8-1ubuntu5_amd64.deb

More info here: https://github.com/Microsoft/BashOnWindows/issues/482

WSL uses the lxrun executable for management from Windows:

lxrun -h

Usage:    /install - Installs the subsystem        Optional arguments:            /y - Do not prompt user to accept    /uninstall - Uninstalls the subsystem        Optional arguments:            /full - Perform a full uninstall            /y - Do not prompt user to accept    /setdefaultuser - Configures the subsystem user that bash will be launched as. If the user does not exist it will be created.        Optional arguments:            username - Supply the username            /y - If username is supplied, do not prompt to create a password    /update - Updates the subsystem's package index

Given that, you can use lxrun /setdefaultuser root. Just thought I'd point out this side of it since it was required when I ran into the same issue as you after trying to upgrade to Xenial. I can confirm that running this command, then the wget / dpkg commands my issues were resolved.

The commands I used:

wget http://mirrors.kernel.org/ubuntu/pool/main/s/sudo/sudo_1.8.9p5-1ubuntu1.4_amd64.debwget http://mirrors.kernel.org/ubuntu/pool/main/p/procps/procps_3.3.9-1ubuntu2_amd64.debwget http://mirrors.kernel.org/ubuntu/pool/main/s/strace/strace_4.8-1ubuntu5_amd64.debdpkg -i sudo_1.8.9p5-1ubuntu1.4_amd64.debdpkg -i procps_3.3.9-1ubuntu2_amd64.debdpkg -i strace_4.8-1ubuntu5_amd64.deb

Finally, you might need to run sudo apt-get install -f in case you get The following packages have unmet dependencies [xxx] but it is not going to be installed

I got rid of the error by moving /etc/hosts to /etc/hosts.bu. After closing the shell en opening again, /etc/hosts is recreated and your computer name is added. The error is gone (for me.)