I am attempting an offline build without success. I have a Guix 1.2.0 node
with internet access on which I download sources with transitive
dependencies:
  $ guix build --sources=transitive tzdata > ~/transfer

I then copy the files as root to a Guix 1.2.0 node without internet access
(only local network access):
  # cat /home/<user>/transfer | xargs -n 1 -I{} scp -p {} <ip>:{}

I then attempt to build on the offline node:
  $ guix build --no-substitutes tzdata

Guix starts downloading and the transferred file is gone! I'm lost as to
why a new download attempt is made as the file data and timestamps match
the original server.

----------------------------------------
The following derivations will be built:
   /gnu/store/83aqdbhnk33p6phd92b48aqb2wlhr7fa-tzdata-2020a.drv
   /gnu/store/0j6gi10v9hz2s2413nhwbzihrydafgvj-glibc-2.31.drv
   /gnu/store/04s4qih73dwvpzpvxs299wcg9dam8f0y-bash-mesboot-4.4.drv
<cut>
   /gnu/store/xxwjr96ihqhpv7ag4cbwzk0r0p5cxakk-tzdata2020a.tar.gz.drv
building
/gnu/store/m5z2bvv96wqhxs4aahjp5xxm910czkhl-tzcode2020a.tar.gz.drv...

Starting download of
/gnu/store/r7xqxgfmm5msvazlzxaccw7h0h6dm898-tzcode2020a.tar.gz
From https://data.iana.org/time-zones/releases/tzcode2020a.tar.gz...
----------------------------------------

Building on the original, internet-connected server no re-download is
attempted, though additional packages not included in the transitive
sources are requested.

----------------------------------------
The following derivations will be built:
   /gnu/store/83aqdbhnk33p6phd92b48aqb2wlhr7fa-tzdata-2020a.drv
   /gnu/store/0j6gi10v9hz2s2413nhwbzihrydafgvj-glibc-2.31.drv
   /gnu/store/04s4qih73dwvpzpvxs299wcg9dam8f0y-bash-mesboot-4.4.drv
<cut>
   /gnu/store/69z1j6lx09krsa019a2r9v72i80lnkql-libsigsegv-2.12.drv
   /gnu/store/0npjqnxv0acwdkxnc6askz2ac4dikj73-libsigsegv-2.12.tar.gz.drv
building
/gnu/store/4lqmlyvbvddzi50cbqjwh8lzb2lvmkia-module-import-compiled.drv...
successfully built
/gnu/store/4lqmlyvbvddzi50cbqjwh8lzb2lvmkia-module-import-compiled.drv
building
/gnu/store/4d3cjvjrgs0q38fs3bgfajcw7apc0vml-Python-3.5.9.tar.xz.drv...

Starting download of
/gnu/store/f99fblkzb6ip268sg096shhs7wzjyp55-Python-3.5.9.tar.xz
From https://www.python.org/ftp/python/3.5.9/Python-3.5.9.tar.xz...
downloading from https://www.python.org/ftp/python/3.5.9/Python-3.5.9.tar.xz
...
 Python-3.5.9.tar.xz  14.7MiB

               141.9MiB/s 00:00 [##################] 100.0%
successfully built
/gnu/store/4d3cjvjrgs0q38fs3bgfajcw7apc0vml-Python-3.5.9.tar.xz.drv
building
/gnu/store/ldkjb6wjcl6dbf0glpfw9f5wh1ia8bq3-bash-2.05b.tar.gz.drv...

Starting download of
/gnu/store/zkkcabiqcy11wy4wkn8bysava6qz8w7v-bash-2.05b.tar.gz
From https://ftpmirror.gnu.org/gnu/bash/bash-2.05b.tar.gz...
following redirection to `https://gnu.askapache.com/bash/bash-2.05b.tar.gz'.
..
downloading from https://ftpmirror.gnu.org/gnu/bash/bash-2.05b.tar.gz ...
 bash-2.05b.tar.gz  1.9MiB

                  4.1MiB/s 00:00 [##################] 100.0%
successfully built
/gnu/store/ldkjb6wjcl6dbf0glpfw9f5wh1ia8bq3-bash-2.05b.tar.gz.drv
building /gnu/store/8nnmv6hfwg543s7b0sbx54ysi514dsz6-bash-4.4.tar.gz.drv...

<cut>
------------------------------

If there is a better way to setup / configure / execute offline builds
please let me know!

Thanks,
Greg