System updates/upgrades: single user mode, and chroot approaches

[Graham Perrin]

On 28/02/2021 23:52, Garance A Drosehn wrote:

Re: Panic after updating from source

> On 28 Feb 2021, at 13:04, Michael Sierchio wrote:
>
>> … if you don't installworld before
>> booting, you can have a mismatch between userland and kernel interfaces.
>>
>> make buildworld && make kernel && make installworld && reboot
>>
>> that always works for me when following a -STABLE branch.
> It may happen to work for you many times in a row, until the day
> it does not work and then you're screwed.  The official instructions
> state that you should always reboot into single-user mode before
> doing 'make installworld'.
>
> The instructions are what they are based on a lot of experience.
> …
>
> We have frequently seen people who are furious when their system
> breaks after they've upgraded from source, and frequently the reason
> their system broke is that they "got away" with cutting corners for
> 20 times in a row.  And then they hit the first time that they were
> not able get away with cutting corners.  And they always blame us
> developers when in fact they're not following instructions.
>
> To quote from /usr/src/UPDATING:
>
>     ... Then, carefully follow the full procedure documented below
>     under the heading "To rebuild everything and install it on the
>     current system."
>     Specifically, a reboot is -> required <- after installing the
>     new kernel before installing world.  While an installworld
>     normally works -> by accident <-  from multiuser after rebooting
>     the proper kernel, there are many cases where this will fail
>     across this upgrade and installworld from single user is
>     required.
>
> …

Thanks to Garance for these insights.

I do routinely read the upper sections of /usr/src/UPDATING however 
until now, I never realised the existence of the COMMON ITEMS section at 
the foot of the page, below the 20131010 line. Not realised because I 
have not used FreeBSD for so long. I stopped paging down, near a point 
in time before which I never updated.

/usr/src/UPDATING might benefit from a hint, near the head of the page, 
to read the COMMON ITEMS section at the foot.

It's remarkable that 
<https://docs.freebsd.org/en/books/handbook/cutting-edge/#updating-src-quick-start> 
makes no mention of single user mode.

----

Upgrade FreeBSD with ZFS Boot Environments | 𝚟𝚎𝚛𝚖𝚊𝚍𝚎𝚗
<https://vermaden.wordpress.com/2021/02/23/upgrade-freebsd-with-zfs-boot-environments/>

– there's a chroot approach to streamlining, where freebsd-update(8) can 
be used. Please, can you think of any special precautions?

Re: 
<https://github.com/helloSystem/Utilities/issues/33#issuecomment-780989454> 
(FreeBSD pure in the midst of a discussion about FreeBSD-based 
helloSystem) if I'm not mistaken, there's an edge case risk of shooting 
oneself in the foot if the user does follow the on-screen instruction:

     Run `/usr/sbin/freebsd-udpate fetch` first.

– at a point during the streamlining where fetch and install need not 
(probably must not) be performed.

Regards
Graham