Re: [yocto] Distro upgrade strategies

["Adrian Bunk" <bunk@stusta.de>]

On Sun, Jun 21, 2020 at 02:09:44PM +0200, Stefano Babic wrote:
> Hi Adrian,

Hi Stefano,

>...
> If it can work in many case, it won't in many other cases. Hash issues with
> packages ? System does not boot and a grub-rescue shell is started ? Not a
> very big problem (in many cases) on server / pc. We check what happens, we
> rework maybe the grub menu, or if nothing works we start a live distro. But
> if this is ok on server / pc for a linux developer, how can it work on
> unattended (embedded) systems, without shell access (due to security
> reasons), and with end users ? It is not enough if it works in most cases,
> it must always work.
>...

one major difference between Yocto and most Linux distributions is that
most Linux distributions enable automatic security updates by default.

A normal Ubuntu system gets security updates installed several times
every week.

I know many nontechnical people working on an Ubuntu laptop or desktop,
and I have seen many embedded systems running Ubuntu.

>...
> I think you mean that dpkg has improved to make the update of a single
> package more atomic, but what about if you upgrade a lot of packages at once
> and you have a power-cut in between ?
>...

What I mean is that what Steve claimed to be "usually" is something 
I do not remember seeing in over 20 years with Debian and Ubuntu.

Not just "improved", this is something dpkg gets right since the 1990s.

As long as any highlevel tool calls "dpkg --configure -a" on unclean
dpkg state, chances are the upgrade can just continue after the power-cut.

With "atomic where they have to be" I meant the normal fsync+rename
that ensures that you can never end up with a half-written file
after a power-cut.

> Best regards,
> Stefano

cu
Adrian