Suggested option for the DVD Installer

[Warren Block]

On Sun, 23 Nov 2014, Rob Diamond wrote:

> My point is that when I followed the default "Guided" option the installer 
> defaulted to GPT, and on exiting the installer my PC wouldn't boot. At this 
> point a FreeBSD noob would have a great deal of difficulty diagnosing the 
> problem, and would most likely give up and try some other distro. For 
> example, I tried installing PC-BSD-10, and after the installer had finished 
> the same PC re-booted fine (it used an MBR layout), and I was away. 
> Previously I've tried Ubuntu and Linux Mint on the same PC, and again both 
> re-booted fine. So I think an extra effort is needed with the installer to 
> get a noob up and running - once they've got something to play with then, OK, 
> expect them to read the manual. But to expect a noob to diagnose the problem, 
> and then manually partition using MBR is unrealistic. And then they're lost 
> to FreeBSD..
>
> Also, there's the following in the FreeBSD manual
>
> "GPT is usually the most appropriate choice for amd64 computers. Older 
> computers that are not compatible with GPT should use MBR. The other 
> partition schemes are generally used for uncommon or older computers."
>
> I think the wording should be a bit stronger than this - something like 
> "Older computers that are not compatible with GPT will not boot from a GPT 
> disk, and must use the older MBR partition type."

The problem there is telling the user how to figure out whether their
computer is not compatible with GPT.

The GPT partitioning scheme includes a "PMBR".  This "protective" MBR is 
there both to protect the GPT partitioning and to allow BIOS computers 
to boot from GPT disks.

In short, it allows GPT to be used with older computers that never 
expected to see anything other than an MBR.  The large majority of older 
computers can boot from the PMBR and use GPT just fine.

However, there are several ways that some vendors messed this up.  The 
most common way was a BIOS that had some extra awareness of partition 
type or layout.  Some vendors did this so they could use their own 
special partitions.  Compaq used to put their BIOS on disk, IBM/Lenovo 
had their own utility partitions, and HP and Acer did similar things. 
Some of these saw the PMBR with its single partition of type 0xee and 
assumed the wrong thing, failing because of the built-in assumptions in 
the BIOS.

Some of these can be cured with a BIOS upgrade.  Lenovo had problems 
with models from three or four years back, and fixed them.

FreeBSD also had a bug in the way it created the PMBR in previous 
versions.  Very strict BIOS or UEFI implementations would then refuse to 
boot.  As far as I know, this problem is fixed in FreeBSD 10.1.