I only have 8GB on the Ubuntu system partition and I am running out of space, so I tried to move the /usr directory (which takes 6GB out of 8GB) to another partition.
I did not want to make a partition only for /usr, so I moved /usr to that partition and made a symbolic link named /usr.
When I restarted my computer, Wifi connection was lost, and Mozc Japanese Input Method did not work anymore. What is the problem with /usr being a symbolic link?
EDIT: I use Ubuntu 16.04, and both partitions are formatted ext4.
EDIT2: When I renamed /usr (in the same partition) and made a symbolic link to that directory, I also got the same problem, so I do not think mounting is the problem.
