From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ricardo Wurmus <rekado@elephly.net>
Subject: Re: Is that normal??
Date: Sun, 20 Oct 2019 12:36:51 +0200
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Jone <yeger9@gmail.com> writes:

> Hi communiti!
> I don't fully understand Guix in this case:
>
> =E2=9D=AF guix pull -l | grep Generation
>    Generation 15    Sep 28 2019 17:10:57    (current)
> =E2=9D=AF guix package -l | grep Generation
>    Generation 155 Oct 20 2019 09:29:25    (current)
> =E2=9D=AF ls -1d /gnu/store/*-gtk+-2.24.32/
> /gnu/store/0v0dwirkd5sixh91n0qby9jzjh8r6m6a-gtk+-2.24.32
> /gnu/store/25sxqwh2x0j04z59yk49nrliz61cwrhd-gtk+-2.24.32
> /gnu/store/386h8ljfhzlpwxjh1682pqh2gxzrxn08-gtk+-2.24.32
> /gnu/store/3z1f2phvbzzjlxr1gvmf5qjprfp5jb7k-gtk+-2.24.32
> /gnu/store/4sdyqsy2np503akvk182xr3510067zgz-gtk+-2.24.32
> /gnu/store/6yabql5aiwnkaqbsi7mvwqiahaswl5ai-gtk+-2.24.32
> /gnu/store/bfa9122w70civ5bz4985h1cli20p0q1b-gtk+-2.24.32
> /gnu/store/ia1vzawl48yqfyg6v2zfxv47kisj49cp-gtk+-2.24.32
> /gnu/store/nzncsbi6d58k7zqzsr4rxyn8inn8pjhm-gtk+-2.24.32
> /gnu/store/wlc89m9yrb65mjbgw0zkabynms0j0xqa-gtk+-2.24.32

A list like this is rarely enlightening, because it=E2=80=99s not clear whe=
re
they are needed (if at all).

> * with the same subfolders *gtk+-2.24.32/{bin,etc,include,lib,share}
> ** and some with the same size
>
> What about deduplication and why different hashes?

What about deduplication?  Deduplication is done at the file level via
/gnu/store/.links.  You can look at the number of links a file has to
see that this actually works:

  $ stat --format=3D%h /gnu/store/3qjd4jfjhd8c8skwlakl677n1fhpmfsr-gtk+-2.2=
4.32/share/doc/gtk+-2.24.32/COPYING
  19

This means that the same COPYING file exists 19 times, but all these
files are hard links to the same single file.  You can also get
(slightly less impressive) numbers for binaries:

  $ stat --format=3D%h /gnu/store/3qjd4jfjhd8c8skwlakl677n1fhpmfsr-gtk+-2.2=
4.32/bin/gtk-builder-convert
  4

Why different hashes?  Different inputs will always lead to different
hashes.  Why different inputs?  Well, either the input package itself
got changed directly, or it has a different hash due to a change in its
inputs.

--
Ricardo