----- I wonder if the upgrade guidance of 18.04 LTS which was released in April come. But it has not come yet. So I upgraded by command execution from the terminal while referring to various sites. It took a lot of time, I got around 30% after 1 hour and I got a screen asking for confirmation of license or something in the middle, but I was not able to proceed as nothing clickable. The environment has already been garbled and the file manager can not be launched. Right click on the file on the desktop and move the necessary files to the external hard disk by moving the file. After all, backing up is essential when fiddling the OS. After all, this PC is halfway state. I wonder if I have to format the hard disk and reinstall OS.