On Wed, Nov 24, 2021 at 08:55:31PM -0500, Leo Famulari wrote:
> Computer A:
> ------
> $ guix time-machine --commit=c70eadeaed9367e45be3797a17d3a34e5f8f67cd -- build --no-grafts hello -d
> /gnu/store/260bk0ch4np4h2yz5yqhf8hjbsyhwpmr-hello-2.10.drv
> ------
> 
> Computer B:
> ------
> $ guix time-machine --commit=c70eadeaed9367e45be3797a17d3a34e5f8f67cd -- build --no-grafts hello -d
> /gnu/store/vs34g0npra395dsqyplrjrwlm417a1w4-hello-2.10.drv
> ------

It's caused by $GUIX_DOWNLOAD_FALLBACK_TEST=none

I noticed by "climbing up" the dependency graph, comparing derivations
until I got to the XZ bootstrap seed derivation on computer B:

------
Derive([("out","/gnu/store/qc9b01x31ayxb36r0zw5cw28awisdq98-xz","r:sha256","1324eb9f74026653255d3a44da3103318e3b8e07f577115d7fa5ae1362eb3345")],[],["/gnu/store/3q889p5zj9kdnl7wfs8dah8wzxvq6j8j-no-content-addressed-mirrors","/gnu/store/chgbsnxxi0032ikjgwi14asmkm792yla-no-disarchive-mirrors","/gnu/store/hdprrnsaa40vl1k63hnq7l1f012jzq2y-mirrors"],"x86_64-linux","builtin:download",[],[("content-addressed-mirrors","/gnu/store/3q889p5zj9kdnl7wfs8dah8wzxvq6j8j-no-content-addressed-mirrors"),("disarchive-mirrors","/gnu/store/chgbsnxxi0032ikjgwi14asmkm792yla-no-disarchive-mirrors"),("executable","1"),("impureEnvVars","http_proxy https_proxy LC_ALL LC_MESSAGES LANG COLUMNS"),("mirrors","/gnu/store/hdprrnsaa40vl1k63hnq7l1f012jzq2y-mirrors"),("out","/gnu/store/qc9b01x31ayxb36r0zw5cw28awisdq98-xz"),("preferLocalBuild","1"),("url","(\"https://git.savannah.gnu.org/cgit/guix.git/plain/gnu/packages/bootstrap/i686-linux/xz?id=44f07d1dc6806e97c4e9ee3e6be883cc59dc666e\" \"https://alpha.gnu.org/gnu/guix/bootstrap/i686-linux/xz?id=44f07d1dc6806e97c4e9ee3e6be883cc59dc666e\" \"http://flashner.co.il/guix/bootstrap/i686-linux/xz?id=44f07d1dc6806e97c4e9ee3e6be883cc59dc666e\" \"http://lilypond.org/janneke/guix/i686-linux/xz?id=44f07d1dc6806e97c4e9ee3e6be883cc59dc666e\")")])
------

It includes all those empty mirror lists, which computer A does not
refer to.

The issue went away when I unset GUIX_DOWNLOAD_FALLBACK_TEST