Re: Unreproducible “guix pack -f docker” because config.scm-builder

[zimoun]

Hi,

On Tue, 02 Feb 2021 at 19:12, Ludovic Courtès <ludo@gnu.org> wrote:

> It turns out that, as is always the case with GNU Standards compliant
> configure script, the default value for --prefix is /usr/local, and the
> default for --sysconfdir is $prefix/etc.

As discussed on IRC, it is not mentioned in the manual.  What the manual
describes is:

  ./bootstrap
  ./configure --localstatedir=/var/
  make

therefore, if one runs:

  ./pre-inst-env guix pull

then the sysconfdir is set to /usr/local/etc because it is the default.
And so it leads to subtle differences really hard to guess.  I think it
is worth to add one sentence or footnote at the end of the section
«Running Guix Before It Is Installed», right after:

        Note that ./pre-inst-env guix pull does not upgrade the local
        source tree; it simply updates the ~/.config/guix/current
        symlink (see Invoking guix pull). Run git pull instead if you
        want to upgrade your local source tree.

Something like: «Note that ’guix pull’ preserves the settings of the host
Guix, for instance ’sysconfdir’, and by default the GNU standards set
’prefix’ to ’/usr/local/’ and ’sysconfdir’ to ’$prefix/etc’, whereas
regular Guix uses ’--sysconfdir=/etc/’.»

WDYT?


> You did find other differences eventually though, right?

The produced tarballs have the same Guix hash, i.e., all the same
inputs, but not the same outputs, compare with commit b9a54aa:


A-machine$ md5sum /gnu/store/nkvlqwzvxdlhzlc7vhfcngxc19x2ay2f-docker-pack.tar.gz
b5fe393d7966cbc3cd0be6e51d3aedc3 
/gnu/store/nkvlqwzvxdlhzlc7vhfcngxc19x2ay2f-docker-pack.tar.gz

B-machine$ md5sum /gnu/store/nkvlqwzvxdlhzlc7vhfcngxc19x2ay2f-docker-pack.tar.gz
e47b9a38b7162f7fb093b97e19dbc1ca 
/gnu/store/nkvlqwzvxdlhzlc7vhfcngxc19x2ay2f-docker-pack.tar.gz

C-machine$ md5sum /gnu/store/nkvlqwzvxdlhzlc7vhfcngxc19x2ay2f-docker-pack.tar.gz
b5fe393d7966cbc3cd0be6e51d3aedc3  
/gnu/store/nkvlqwzvxdlhzlc7vhfcngxc19x2ay2f-docker-pack.tar.gz


And diffoscope returns these differences, something about links, IIUC:

--8<---------------cut here---------------start------------->8---
--- 
/tmp/docker-meary/4ca83868d5e98cb06179a2a7372afe029c10d43bdc9fbfcc5771b89da74889b8/layer.tar
+++ 
/tmp/docker-pfiuh02/4ca83868d5e98cb06179a2a7372afe029c10d43bdc9fbfcc5771b89da74889b8/layer.tar
├── file list
│ @@ -823,17 +823,17 @@

[...]

│ --r-x… 29960 
gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/libexec/getconf/POSIX_V6_LP64_OFF64

[...]

│ +hr-x…     0 
gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/libexec/getconf/POSIX_V6_LP64_OFF64

[...]

├── 
gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/libexec/getconf/POSIX_V6_LP64_OFF64
│ @@ -1,1873 +0,0 @@
│ -00000000: 7f45 4c46 0201 0100 0000 0000 0000 0000  .ELF............
│ -00000010: 0200 3e00 0100 0000 3015 4000 0000 0000  ..>.....0.@.....
│ -00000020: 4000 0000 0000 0000 486d 0000 0000 0000  @.......Hm......
│ -00000030: 0000 0000 4000 3800 0b00 4000 1f00 1e00  ....@.8...@.....
│ -00000040: 0600 0000 0400 0000 4000 0000 0000 0000  ........@.......
│ -00000050: 4000 4000 0000 0000 4000 4000 0000 0000  @.@.....@.@.....
│ -00000060: 6802 0000 0000 0000 6802 0000 0000 0000  h.......h.......

[...]
--8<---------------cut here---------------end--------------->8---

(Slightly edited to ease the reading, and raw at
<https://paste.debian.net/1183728/>.)


On machines A and C, empty file because hard link.  But on machine B,
the files are there.  Tiny files I guess, the size difference is:
23104 vs 23136.

Cheers,
simon