Re: restic backup with btrfs /

[Christoph Hellwig <hch@infradead.org>]

On Mon, Jun 30, 2025 at 11:07:06AM +0100, Mark Harmstone wrote:
> On 28/06/2025 6.33 pm, Ulli Horlacher wrote:
> > restic (https://restic.net/) is a great backup tool but has some
> > limitations or design flaws: one is, it believes that any subvolume is on a
> > different filesystem. This means: "restic backup --one-file-system /" will
> > only backup the root subvolume, but no other subvolumes like /home
> > /var/spool etc...
> > 
> > One has to add every subvolume to the argument list. Bad if you
> > create new subvolumes and forget to update the backup cronjob.
> > When you later need to restore a file, there will be none...
> 
> This is a bug in Restic that needs to be fixed, though they may not see
> it that way.

.. because it isn't.  btrfs is the buggy one here breaking the old
Unix tradition also (somewhat vaguely) encoded in Posix that st_dev must
not changed except at a mount point.