ZFS and GPT boot - size issue bootblock v.s. default of sysinstall

[Allan Jude]

On 2016-12-30 07:33, Dirk-Willem van Gulik wrote:
> 
>> On 28 Dec 2016, at 22:04, Allan Jude <allanjude at freebsd.org> wrote:
>>
>> On 2016-12-28 14:41, Dirk-Willem van Gulik wrote:
>>> On a default ZFS install (late 2014, 10.x) of a few years hence it seems sysinstall selected 64k as the default size of partition 1: with the bootblock:
>>>
>>> sudo gpart show
>>> =>        34  7814037101  ada0  GPT  (3.6T)
>>>          34           6        - free -  (3.0K)
>>>          40         128     1  freebsd-boot  (64K)
>>>         168    67108864     2  freebsd-swap  (32G)
>>>    67109032  7746928096     3  freebsd-zfs  (3.6T)
>>>  7814037128           7        - free -  (3.5K)
>>>
>>> …. lots of disks snipped …..
>>>
>>> =>        34  7814037101  ada35  GPT  (3.6T)
>>>          34           6        - free -  (3.0K)
>>>          40         128     1  freebsd-boot  (64K)
>>>         168    67108864     2  freebsd-swap  (32G)
>>>    67109032  7746928096     3  freebsd-zfs  (3.6T)
>>>  7814037128           7        - free -  (3.5K)
>>>
>>> Fair to assume that this (the 64k) is the reason that from 11.x onwards; 
>>>
>>> 	gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada0 
>>>
>>> fails with an immediate:
>>>
>>> 	gpart: /dev/ada1p1: not enough space 
>>>
>>> as gptzfsboot has grown in recent years to something towards the 90k mark ?
>>>
>>> 	-r--r--r-- 1 root wheel 88898 Dec 24 11:52 /boot/gptzfsboot
>>> 	
>>> And I guess avoiding a rebuild would mean something like gently disabling swap; shifting partition 1 & 2 carefully an so on ? Or is there a more clever way? ZFS has *already* been upgraded.
>>>
>>> Or am I missing something ?
>>
>> swapoff -a; gpart resize ...; swapon -a
>>
>> is likely your best bet.
> 
> Aye - indeed a
> 
> 	#!/bin/sh
> 
> 	# gen 0 35 | while read I
> 
> 	camcontrol devlist | grep ada | awk -F, '{ print $2 }' | sed -e 's/)//‘ | while read I
> 	do
> 		gpart delete -i 2 ada$I
> 		gpart resize -i 1 -s 512k ada$I
> 		gpart add -t freebsd-swap -i 2 ada$I
> 		gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada$I
> 	done
> 
> solved the issue for all machines affected. 
> 
> We’ve since spotted quite a few systems with too small a bootblock - so I guess sysinstall has historically been a bit stingy - and it may be an idea to include something like above logic in man-page or the upgrade logic.
> 
>> The other option is to rebuild gptzfsboot without GELI support, and then
>> it will be under 64 KB.
> 
> Unfortunately - we rather rely on GELI and PKCS#11.
> 

This would only apply to gptzfsboot, the new feature I introduced in
11.0 that allows you to have even the /boot directory encrypted (rather
than having an unencrypted ufs partition, or a 2nd zpool that is not
encrypted).

If you are upgrading from 10.x or earlier, you can use gptzfsboot
without GELI, since it didn't exist before.

> Dw.
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-- 
Allan Jude