Re: Snapshots of individual files

[Roman Mamedov <rm@romanrm.net>]

On Tue, 23 Dec 2025 00:43:25 +0000
BP25 <bp25@posteo.net> wrote:

> Hello,
> Can any of you guys help me understand why it hasn't been made possible 
> to snapshot individual files? Because technically it's trivial to 
> implement therefore I suspect there must be some abstract reason... The 
> only thing I can think of is the case where some file which was 
> snapshotted is then deleted hence there is no way to 'select such file' 
> and ask btrfs for the snapshotted versions... but even in this case I 
> see no problem: either the convention is that when you delete a file 
> then all snapshots of such individual file are also deleted, or better 
> there is a command that shows all files who have been deleted but have 
> have been snapshotted in the past.
> Any ideas?
> Please CC or BCC me cause I'm not subscribed.

You can make "snapshots" of a file with:

  cp -a --reflink filename filename.snap

from what I tested this appears to be atomic (entire file is reflinked at
once), someone might correct me if I'm wrong.

Works on modern XFS too.

-- 
With respect,
Roman