重設windows10中的子linux系統密碼

1. Run bashand make a note of your Linux username (this need not match your Windows username)

2. In Windows admin command prompt (Super+X, A) change the default user to root:

   lxrun /setdefaultuser root
   

3. Now Bash on Ubuntu on Windows logs you in as root without asking password

4. Use passwd command in Bash to change the user password:

   passwd your_username
   

5. Change the default user back to your normal user in Windows command prompt

   lxrun /setdefaultuser your_username

From http://askubuntu.com/questions/772050/reset-the-password-in-linux-bash-in-windows