[systemd-devel] [PATCH/resend] Use reflinking to copy kernel

[Lennart Poettering]

On Mon, 18.05.15 13:56, Simon McVittie (simon.mcvittie at collabora.co.uk) wrote:

> On 18/05/15 13:15, Lennart Poettering wrote:
> > --reflink=auto is the default in cp since a while.
> 
> I think you're thinking of recent mv versions, or a patched
> coreutils?

Oh indeed, I noticed this behaviour on mv...

> I believe the rationale is that people invoking cp(1) might expect to
> have two entirely independent copies of all the file's disk blocks
> afterwards, such that a kernel- or hardware-level bit-flip in one would
> leave the other untouched - as opposed to reflinking, in which
> *user-space* changes to one leave the other untouched. I don't
> personally think that rationale is sufficiently convincing to outweigh
> the simplicity of reflinking by default, but I don't maintain coreutils,
> and perhaps I'd think differently if I did.

Yeah, I very much disagree with that upstream decision too... I mean,
if people really want byte copies they should think in terms of "dd"
not "cp"...

Lennart

-- 
Lennart Poettering, Red Hat