After updating Ubuntu to 16.04, "Cannot add user, all the user directories are read-only."

Question

Yesterday, I unsuspectingly updated Ubuntu to 16.04 without realizing that it would allow me only to install MySQL 5.7, unsupported by JIRA.  So, after downgrading to MySQL 5.6, I was unable to get past the Administrator User addition stage; I always get "Cannot add user, all the user directories are read only".  I have tried 2 full reinstalls of JIRA and nothing has worked, including deleting my jiradb database and jiradbuser multiple times.  Tomorrow, I will wipe completely MySQL and see if I can re-add only my previous jiradb to the new database.  Does anyone have any clues what I can do next?  I have deleted all folders inside /opt/atlassian/JIRA and deleted my home directory.  Why doesn't a full reinstall work?  Did MySQL 5.7 break my database so it no longer works with version 5.6?  When will MySQL 5.7 support come to JIRA?  Should I just go back to Ubuntu 14.04??

David Rhoderick · Accepted Answer

Of course, the simplest solution was the one that worked; restarting.  After restarting (and returning with a bit more patience today), I had to fix ulimit on my MySQL installation, but I was able to connect.  I think finished restoring my system from an old database and home folder by going through the steps from https://answers.atlassian.com/questions/195807