Re: tar extract changed since netbsd-8? (extracting sets over running system)

[Greg Troxel <gdt%lexort.com@localhost>]

David Brownlee <abs%absd.org@localhost> writes:

> On Tue, 12 Nov 2019 at 11:33, Jaromír Doleček <jaromir.dolecek%gmail.com@localhost> wrote:
>>
>> Le mar. 12 nov. 2019 à 12:05, Martin Husemann <martin%duskware.de@localhost> a écrit :
>>>
>>> Not seen this locally, but that would be the switch to bsd/libarchive tar.
>>> Maybe it does not unlink files before extraction and replaces them in-space?
>>>
>>> I do the same kind of updates, but usually on a very quiet system.
>>>
>>> The crashes you see are from other running processes? Joerg would likely
>>> say: "don't do that" ;-)
>>>
>>
>> I thought we do unlink by default, I think I remember a commit to that effect in past. The unlink is very useful default behaviour of GNU tar. In-place overwrite is very rarely the wanted behaviour.
>
> Aha thanks!
>
> I would argue the switch to unlink no longer being the default is a
> regression. If its mandated by standards or we're the only outlier
> then it probably makes sense to switch, but otherwise its sprinkling
> occasional non deterministic breakage across a bunch of scripts which
> previously ran fine on NetBSD.

I'm not quite clear on 'unlink by default', but it seems to me the
replacement files should be written to a temporary name and then
renamed() into place so the file is either the old version or the new
version.

Despite it being technically irregular, unpacking sets on a running
system is a very normal thing to do.

So I'm with abs@ ont this - the old behavior should be default.