Re: Possible to undo subvol delete?

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

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On 2014-11-29 23:23, Marc MERLIN wrote:
> On Sun, Nov 30, 2014 at 09:03:14AM +0530, Shriramana Sharma wrote:
>> IIUC with BtrFS while it is possible to easily undelete a file or
>> ordinary directory if a snapshot of the containing subvol exists, it
>> seems that it's not elementary to undelete a subvol itself, because
>> all subvols are under the root-level subvol (id 0 or 5, see my other
>> q) but even snapshotting the root subvol will not snapshot any subvols
>> under it.
>>
>> So is there any way to undo a subvol delete?
>
> If you didn't snapshot that volume before deleting it, you're SOL.
> If you snapshotted it, rename that snapshot to the other name, and
> you're done.
>
> Btrfs doesn't offer undelete, it only lets you keep multiple copies of
> your data at very little cost, so you can retrieve a snapshot copy if
> you deleted your current volume's data.
>
> Marc
>
Well, in theory, if you unmount the FS _immediately_ after the subvol 
delete, without writing _anything_ else to it, it _might_ be possible to 
recover the data using some (probably almost incomprehensible) 
incantation of btrfs-find-root and btrfs recover/restore.

In practice though, for anyone who doesn't have expert level knowledge 
of the on-disk structure and fs internals, deleting a subvolume can't be 
undone.

We might want to consider adding an option to btrfs subvol del to ask 
for confirmation (or make it do so by default and add an option to 
disable asking for confirmation).


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