Snapshotting for rollback after updates was[ Re: Drawing lessons from fatal SELinux bug #1054350]

Reindl Harald h.reindl at
Sun Jan 26 21:07:55 UTC 2014

Am 26.01.2014 21:56, schrieb Chris Murphy:
> On Jan 26, 2014, at 1:07 PM, Reindl Harald <h.reindl at> wrote:
>>> Well, the mail servers regularly get updated by the company I pay for such things, and I've 
>>> never noticed the change. It uses IMAP so I don't think the server even cares, its just a bunch 
>>> of folders and files
>> blabla - nobody talks about the mailserver
> Jerk. Simo said, in the line right above this that you cut: "There are many other examples like this especially on the server side."

be careful in which context you somebody calls a Jerk

>> the topic is *internal* data of *local* software
>> you may have luck and nothing happens
> This was not at all made clear from the start, it was assumed by people who understood

because that people thought somebody with that much replies
to the thread would have understodd the topic

> I explicitly asked if I was on the same page or not. Instead of bringing me up to speed, 
> you decide to be condescending. Congratulations on your rudeness

as you can see some lines above you needed *exactly* that way of comminucation
to understand what we are talking about in this thread - this is the *dvel* list
and so technical understanding is implicit in a discussion

>> with bad luck you even won't realize that there are new mails you never face
>> because of happy upgrade/downgrade internal caches are accessed with
>> *undefined bahvior*
> Email are user documents the same as a Libreoffice document. You do not get to say that just 
> because it's a semi-hidden database, that its file format is allowed to change in a downward 
> incompatible manner

what exactly did you not understand in the two words "internal caches"
frankly i faced mail clients where you needed to remove the complete
IMAP account to stop not display any new or moved message in specific

>> any software on that planet will recognize upgrades and convert *internal* data
>> but nobody will give you a warranty how the same software behaves after a downgrade
> Well insofar as the whole software EULA paradigm basically says for any reason, willful 
> or not, they can blow up your data in any direction possible and there is no liability 
> claim whatsoever… what you're saying doesn't even apply to upgrades.

google for "undefined behavior"

>> yes, in most cases nothing bad happens
>> in rare cases you recognize the problem and find a solution
>> in some cases you even don't recognize that internal things are slightly going wrong
> It's no worse a risk than a conventional reversion with a clean install

well, i never re-installed any linux system in my life for good reasons
the same reasons i never would restore a snapshot of my whole filesystem
or even more worse *a complete tree* alone of it

> So I fail to see how any of this relates to snapshots

that you fail to see the possible impact of a snapshot-restore is obviously
and you do not need to repeat that again and again

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