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

Chris Murphy lists at
Sun Jan 26 20:56:48 UTC 2014

On Jan 26, 2014, at 1:07 PM, Reindl Harald <h.reindl at> wrote:

> Am 26.01.2014 20:56, schrieb Chris Murphy:
>>> What about mail application change the format of the mail folders ?
>> Good question because I experienced this recently. So the way Apple does this on OS X with Mail, 
>> there is no such thing as a mail format change during the life of a major OS version. So major 
>> OS versions are 10.7, 10.8, and now 10.9
> and you have a warranty for that?

It's a long standing expectation and tradition, and considering millions of users had this sort of behavior occurred by now no doubt I'd have heard about it.

>> I can upgrade and downgrade all along 10.7.x and the file format is the same.
> you *think* that

If there is a change, it's not a downward incompatible change.

>> Recently I learned that there are two mail formats. There's the every day used format that 
>> is apparently completely incompatible between major versions of Mail
>> I can export 10.8 Mail in this format, and 10.7 Mail can also read it. And even this pissed 
>> me off as well as several thousand users (at least) based on Apple's community forums on the 
>> subject because most of us expect to be able to directly import 10.7 mail into 10.8 Mail. 
> where you prove that what you said above is wrong

No you just have reading comprehension problem. The minor versions are compatible. The major versions aren't.

>> 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."

> 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. 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.

> 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. I will disagree with that position at every possible turn as something between sloppy programming and dereliction.

> 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.

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

Chris Murphy

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