I don't believe all of this is true. I chose to upgrade my kernel yesterday to 2.6.38-8 and it was added as the final option on the grub menu but not the default. The default stayed as it was. Becoming default may have been true for a short while, but I think that the original behavior was to add it as another option, but not default.
Yes, it is true. You can verify it for yourself. If you chose the default option in the GRUB boot menu, then open a terminal and enter uname -r
. It will show the kernel version last installed.
The reason is that /boot/vmlinuz is a soft link to the default kernel. In my case, it would be vmlinuz-220.127.116.11-pclos1.a64. To find which one is default on your system, open a terminal and enter:ls -l /boot/vmlinuz
You can see, in my case, which file is pointed to by the vmlinuz link.lrwxrwxrwx 1 root root 27 Jun 4 09:54 /boot/vmlinuz -> vmlinuz-18.104.22.168-pclos1.a64
When you install a new kernel in Synaptic, the vmlinuz soft link is updated to point to the kernel just installed.