Open a terminal and run sudo umount /tmp or, if that fails, sudo umount -l /tmp
and then:
sudo mount -t tmpfs -o size=7G,mode=1777 overflow /tmp
sudo mount -t tmpfs -o size=7G,mode=1777 overflow /dev/tmp
or
mount -o remount,size=5G /tmp/
print size of /tmp:
df -h /tmp
