After installing opennebula in frontend,
File /var/lib/one/one.db doesn’t exist
And an error message displayed “ONE_AUTH file not present”
Check if you have /var/lib/one/.one location. one_auth file is located there. It happened to me as well, luckily I had a full copy of the /var/lib/one folder and just copied all the files, restarted the opennebula service and the problem was solved.