Recipes for Ubuntu linux on Toshiba laptops

I started this section in March 2009 after installing Ubuntu 8.10 on a Toshiba Portégé R600 laptop to replace a MacBook Pro that I didn't like.  Summary:  the Portégé R600 proved a great computer except for its fan noise, and a far better daily companion than my MacBook Pro.  Ubuntu worked very well on it.  The basic installation was easy, but many applications needed laborious nontrivial fine-tuning.  Adaptation to my preferences and habits took weeks of heavy googling.  I then posted the details here to make such a job easier for others like me.  In December 2009 I added hard-learned recipes "how not to sudo-cide Ubuntu and how to revive it if you do", and "how to undo an Ubuntu update".  Since then I installed Ubuntu 12.04, Ubuntu 14.04 and Ubuntu 18.04 on successive Toshiba Portégé laptops.