An observation (kernel 3.13.0-155 is broken WRT Java) and a Grub2 / Ubuntu question

[Robert Heller]

OK, I just did updates at the local library, where the machines (except the 
server's bare metal) run Ubuntu 14.04 LTS.  The kernel update (3.13.0-155) 
crashes (sort of) when you try to run a Java program (specificly the Arduino 
IDE (1.8.5)).

My question is this: what is the "magic" to change the default kernel to boot? 
With the grub2 configuration "magic" it is not a simple matter of changing one 
line /boot/grub/grub.conf, but seems to require something far more arcane and 
there does not seem to be a simple man page that explains this.  Sigh...

On the two laptops I did the "brute force" method of just purging
(uninstalling) the 3.13.0-155 kernel (I'll have to go back and do the hack to
prevent updating the kernel). The PXE booted machines were easier -- I just
manually changed the symlinks in the tftp boot directory.

-- 
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