installing a mirror for offline installation

[Quiliro]

I finally could install bare-bones.scm GuixSD working machine. Now i am 
interested in installing a mirror [of hydra] for offline installation. There is 
no telecommunications where I live. So I could bring the server to download 
substitutes and then take it back to my network for local download. I was told 
that an nginx mirror of hydra would cache only substitutes after they have been 
requested through it. Nevertheless, for those that need that, here is the 
config:
https://git.savannah.gnu.org/cgit/guix/maintenance.git/tree/hydra/nginx/mirror.conf

Since that solution is not for offline use, please suggest what I should do. 

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