官方指导：https://docs.gitlab.com/ce/security/reset_root_password.html
How to reset your root password
To reset your root password, first log into your server with root privileges.
Start a Ruby on Rails console with this command:
gitlab-rails console -e production
Wait until the console has loaded.
There are multiple ways to find your user. You can search for email or username.
user = User.where(id: 1).first
or
user = User.find_by(email: \'admin@example.com\')
Now you can change your password:
user.password = \'secret_pass\'
user.password_confirmation = \'secret_pass\'
It’s important that you change both password and password_confirmation to make it work.
Don’t forget to save the changes.
user.save!
Exit the console and try to login with your new password.