Re: Default MBR boot "manager"

On Nov 11, 2013, at 1:43 PM, Nathan Whitehorn wrote:

> On 11/11/13 15:39, Teske, Devin wrote:
>> On Nov 11, 2013, at 1:32 PM, Nathan Whitehorn wrote:
>> 
>>> On 11/11/13 15:19, Teske, Devin wrote:
>>>> Topic: Lenovo Laptops and bsdinstall zfsboot with MBR layout...
>>>> 
>>>> Should we do the quick patch to change the default
>>>> from /boot/boot0 to /boot/mbr:
>>>> 
>>>> Index: zfsboot
>>>> ===================================================================
>>>> --- zfsboot     (revision 258016)
>>>> +++ zfsboot     (working copy)
>>>> _at__at_ -764,7 +764,7 _at__at_ zfs_create_diskpart()
>>>>                 #
>>>>                 f_eval_catch $funcname gpart "$GPART_CREATE" mbr \$disk ||
>>>>                              return $FAILURE
>>>> -               f_eval_catch $funcname gpart "$GPART_BOOTCODE" /boot/boot0 \
>>>> +               f_eval_catch $funcname gpart "$GPART_BOOTCODE" /boot/mbr \
>>>>                              \$disk || return $FAILURE
>>>> 
>>>>                 #
>>>> 
>>>> That would fix things for Lenovo laptops for the next
>>>> release until I finish up the bootcode selection menu.
>>>> I'd like to take my time in making sure Allan and I design
>>>> a worthy bootcode selection menu.
>>> This patch looks good (I don't remember why it was boot0 in the first place). I think gpart automatically installs something like /boot/mbr by default, so I'd be interested to know if making the diff purely negative still works.
>>> 
>>> On another note, I think we should move away from a selector. Right now, we have three kinds of boot code:
>>> 1. ZFS boot code
>>> 2. UFS boot code
>>> 3. boot0
>>> 
>>> Unifying 1 and 2 would help a lot -- I don't know of any reason we need both except for tradition. #3 is probably best done as a post-install config step ("Install FreeBSD boot manager" or something), which also means it works for UFS systems.
>> Well, I'm sensitive to the fact that sysinstall offered "none" and
>> even explained why in an F1 dialog that brought up "drives.hlp"
>> to explain that you might want to keep whatever (alternate) boot
>> manager you may be using already.
>> 
>> In a proposed selector, the full breadth of options that I was
>> envisioning was:
>> 
>> GPT + gptboot
>> GPT + none (use your existing boot manager... syslinux?)
>> MBR + mbr
>> MBR + boot0
>> MBR + none (again, BYOBM)
>> 
>> Hadn't got around to zfsboot yet. Where would that go? at the top?
>> 
>> GPT + zfsboot ?
>> 
>> (and of course, this is x86 specific... I was gleaning from sysinstall
>> that for systems like pc98, they call it an IPL and there's only two
>> options... a standard IPL or bring your own boot manager, aka "none").
>> 
>> I imagine that there would be architectures that are like the ol' pc98,
>> wherein they don't have all these options (is, for example? sparc64
>> GPT only?)
> 
> This would be super-unportable. SPARC uses VTOC8, for example, and doesn't support GPT at all. PC98 has the differences you mentioned. PowerPC uses MBR sometimes, sometimes APM, sometimes GPT. You never have a choice. No platforms except x86 have any analog to boot0. Etc, etc. This is why I'd like to pull ZFS into partedit, which already knows how to set up everything and does the right thing everywhere. For the only system (x86) where there is a real choice (do you want to replace whatever you have already with boot0?), it makes sense to do this as a post-install config.

Two migration paths before us, and I do rather like the idea of
benefiting from all your work there.

My biggest concern is how to maximize functionality in the
migration of the ZFS stuff to partedit.

You know the code better there better than I, ... have you given
much thought to how you might integrate what we've done?

It's sad that we would be giving up i18n, X11, and discrete
scripting (surely there are more parts to ZFS than what partedit
supports now -- e.g., datasets, etc.).

Naturally, the scripting can be solved. i18n is a bit harder to
solve as it's a "start from the bottom" venture. And I fear X11 is
a lost cause in its current state for partedit.
-- 
Devin

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