Fix of "sessionname_not_client" error of the Kloxo/HyperVM

[Fli]

How to fix the error "sessionname_not_client" provided by Kloxo or HyperVM?

I read that the cause can be not enough disk space on the HDD or the wrong permissions (not writable) on /tmp

To discover disk usage, on can login via SSH and execute command: df -h