I have worked out a way to do this. What I did is as follows.
Copy the extension(s) needed to connect to the internet to a new directory. (This step may not be necessary, but playing it safe.)
Run with the options: base norestore text.
At the prompt, type: startx
Open the terminal and type:
sudo su
mount /mnt/sda1 (use appropriate partition)
Open the Appbrowser, and use Install Local. (You can click ../ a few times, to go up and find /mnt/sda1 or the appropriate partition.)
Connect to the internet.
Select Update Extensions from the menu.
[removed due to policy violation]/update-programs.html