Mailinglist Archive: opensuse (1620 mails)

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Re: [opensuse] Re: btrfs (with subvolumes) & raid-1 setup
В Sat, 22 Nov 2014 13:34:16 -0500
Anton Aylward <opensuse@xxxxxxxxxxxxxxxx> пишет:

On 11/22/2014 09:38 AM, arvidjaar@xxxxxxxxx wrote:
I think this the only setup that makes sense in the long run. I do not know
if yast supports it though.


Please explain why you feel it is the only setup that makes sense.


You install new updates and create snapshot before it. Your primary
filesystem is in btrfs root and snapshot goes in some subvolume
(/.snapshot/backup or anything). You reboot and find that your system
does not boot or is not usable. What are your options to go back to
working backup?

1. Copy files from backup snapshot back into root.

It is time consuming, defeats space saving by inflating root and may
not be that trivial if directory structure changed.

2. Mount backup snapshot as root.

So we are exactly in the situation we discuss. We end up with root on
subvolume without explicit support from system management tools.

3. Set default volume to backup snapshot

Probably just as unsupported as 2; also it raises hairy questions like
"what / now refers to, like in /.snapshot".

If your root is on subvolume from the very beginning and all tools are
known to support it, fallback is trivial. You are on /@/root-current,
you create /@/root-backup; if boot from /@/root-current fails, just
point to /@/root-backup and continue to work.

Second consideration is that "backup before install" is backward. It is
not safe to update running system, even if update looks very innocent.
The only sure way is to clone current system, update clone (while
running your current system) and reboot into clone. And current model
simply does not provide for it.
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