Mailinglist Archive: opensuse-factory (745 mails)

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Re: [opensuse-factory] btrfs /var changes

Le 21/01/2018 à 19:21, Richard Brown a écrit :
On 21 January 2018 at 15:43, Antoine Belvire
<antoine.belvire@xxxxxxxxxxx> wrote:

I've moved to the new layout so I've written something on how to do it:

The explanations are in French but the commands are the same in English ;-)

This guide is wrong, dangerous, and should not be followed


_I strongly recommend against anyone using this guide_

To summarise it's key flaws

#1 The guide does not make clear that the new structure should NOT BE
USED on Leap 42.3 or earlier distributions.
Anyone using a flat /var subvolume on Leap 42.3 or earlier WILL break
their system when rolling back because rpm still locates it's database
in /var/lib/rpmdb in that version, and hundreds of packages store
their fillup-templates in /var/adm still.

The explanations in French that accompany the commands (especially on page 1: makes clear that this is for Tumbleweed and only that Tumbleweed has performed the necessary changes to be able to do that.

And that there are already pretty clear warnings that say that no one who does not understand the commands should perform them.

So this particular point is invalid to me.

#2 The guide assumes @ is the correct subvoulme to add the new /var.
This is incorrect for many many users.
@ does not exist on any installations that are upgraded from old
release versions of openSUSE (including installations of Tumbleweed
circa 2015 or earlier - it was only introduced around the period of
Leap 42.1 IIRC)

True. I could precise this. I installed Tumbleweed when there was no @. I added it a few months ago. Not very complicated too.

3. Even if you correct the guide to address #1 and #2 the guide does
nothing to address the fact that every single snapshot will be
invalidated, as your old snapshots will still include contents in /var
but your root filesystem will now have /var as a subvolume.
I admit I am not sure of the consequences of trying to rollback to an
old subvolume in this case, but I imagine they will not be pretty.
Has anyone tested this? I haven't because the lack of a clear
solutions to #1 and #2 put the need for this at the bottom of my list.

True, I didn't write information about this.

I guess that if old snapshots are restored then the content in old directory /var would be restored, the new @/var subvolume would just exist without being mounted. I think the main problem would be the old subvolumes below var and their contents which are lost.

One could try to keep these subvolumes instead of deleting them and just remove them from fstab, I don't know if it's enough to keep rollback possible.

Please, either correct the document with clear answers to the above
issues or remove the guide as soon as possible.
Anyone following your guide is at risk of breaking their system,
whereas anyone leaving their structure alone, like I intended, will
have no problems for the foreseeable future.

I won't remove this "guide", thank you. Anyway you've made clear that you don't support it :-P

I may add/improve warnings for #2 and #3 though.

My aim is not to deliver a universal guide - I would have started by writing in English. It just works for me. I hope it can help others.


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