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

[Dirk-Willem van Gulik]

> 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.

Dw.