cd /path/to/owncloud sudo -u webserveruser php occ user:resetpassword adminaccountnameIn our case the command was:
cd /var/www/cloud sudo -u www-data php occ user:resetpassword adminIt should prompt you for your password twice:

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cd /path/to/owncloud sudo -u webserveruser php occ user:resetpassword adminaccountnameIn our case the command was:
cd /var/www/cloud sudo -u www-data php occ user:resetpassword adminIt should prompt you for your password twice:
net user [username] *In this case:
net user administrator *You will be prompted to enter a new password without having to provide the existing password first. To get a list of the users on the system, you can run:
net usersUse this for good, not evil!