Flood of "Couldn't flush user prefs: java.util.prefs.BackingStoreException: Couldn't get file lock."

[mccartney]

In Confluence logs you can observe a flood of message like this one:
2016-11-24 20:11:20,004 WARN [Timer-0] [java.util.prefs] log Couldn't flush user prefs: java.util.prefs.BackingStoreException: Couldn't get file lock.
That goes in hundreds.

[mccartney]

Which seems to match with: https://confluence.atlassian.com/confkb/could-not-lock-user-prefs-unix-error-code-2-670958391.html

and they point to the problem of the user (running Conflu) not having write permission to its own home directory, which seems to match my observations:

$ docker exec -it 257 /bin/bash
daemon@257f7231c538:/var/atlassian/confluence$ touch $HOME/z
touch: cannot touch ‘/usr/sbin/z’: Permission denied

[mccartney]

This seems not to be a general Confluence behavior. I suspect this might be the 'fault' of the Visibility plugin.

Still, it's true the daemon user doesn't have privileges to its home directory.