by default sonar creates admin account : user: admin, password : admin
when sonar admin password is changed and lost, simple way to reinitialize password to admin is with a simple sql command :

musql -u sonar -p
mysql> use sonar
mysql> update users set crypted_password = ‘88c991e39bb88b94178123a849606905ebf440f5’, salt=’6522f3c5007ae910ad690bb1bdbf264a34884c6d’ where login = ‘admin’
that’s all.