Try this solution:
Locate the database file grafana.db. It should be somewhere in /var/lib/grafana.
- Connect to the database.
$ sqlite3 /path/to/grafana.db - Check for admin login.
sqlite> select * from user; - Update the user’s password.
update user set password = '59acf18b94d7eb0694c61e60ce44c110c7a683ac6a8f09580d626f90f4a242000746579358d77dd9e570e83fa24faa88a8a6', salt = 'F3FAxVm33R' where login = 'admin';
*The password is “admin”.