I am a linux fresher. I make a folder /dev/test/ in Ubuntu. When I rebooted the server, the folder /dev/test/ was disappear. Can restore the folder? Why?
Device file system in Linux is not a filesystem stored on disk. See this wikipedia article. In kernel 2.6 series it is devtmpfs and is managed by udev.
In short the things you do in /dev filesystem do not persist through reboot.