So indeed, it worked. Through the web interface, I chose to update from 6.1.1-15101 to 6.1.2-15132. After rebooting, the web interface does not come back. I logged in through the serial connection (using the same login info as web interface), and did following two commands:
sudo cp /lib/modules/update/* /lib/modules
sudo reboot
(After the first command, I had to type my password once more)
So it rebooted and I could log in again through the web interface, and the version was indeed 6.1.2-15132.
Thanks very much everyone, for the valuable information.