Hi,
in the same way as you would reset your root password, following the docs:
Log into the rake console, this may take a while. Also, use with care, this step is performed as root and open heart surgery.
gitlab-rails console -e production
Next, find the user you want to make an administrator. E.g. by email, or any other attribute which fits.
user = User.find_by(email: 'kurt@domain.com')
or
user = User.find_by(username: 'kurt')
The next step is to change the admin flag and save the changes.
user.admin = true
user.save!
Then leave the console with exit.
Please let me know whether this worked for you.
Kind regards,
Michael