With current ‘master’, fixed-output derivations are not substituted, even though a substitute is available:
--8<---------------cut here---------------start------------->8--- $ guix build -S acct The following file will be downloaded: /gnu/store/0sszdqmiqmb4mzbgs8h2185fh7p8bfd2-acct-6.6.1.tar.gz @ build-started /gnu/store/b7c2lgbdnr5anzklxkzhjvqxl14n7cqp-acct-6.6.1.tar.gz.drv - x86_64-linux /var/log/guix/drvs/b7//c2lgbdnr5anzklxkzhjvqxl14n7cqp-acct-6.6.1.tar.gz.drv.bz2 starting download of `/gnu/store/0sszdqmiqmb4mzbgs8h2185fh7p8bfd2-acct-6.6.1.tar.gz' from `http://ftpmirror.gnu.org/acct/acct-6.6.1.tar.gz'... following redirection to `http://gnu.cardse.net/acct/acct-6.6.1.tar.gz'... http://gnu.cardse.net/.../acct-6.6.1.tar.gz 100.0% of 2802.4 KiB @ build-succeeded /gnu/store/b7c2lgbdnr5anzklxkzhjvqxl14n7cqp-acct-6.6.1.tar.gz.drv - /gnu/store/0sszdqmiqmb4mzbgs8h2185fh7p8bfd2-acct-6.6.1.tar.gz $ sudo cat /var/guix/substitute-binary/cache/0sszdqmiqmb4mzbgs8h2185fh7p8bfd2 (narinfo (version 1) (cache-uri "http://hydra.gnu.org";) (date 1413472751) (value "StorePath:... $ guix build -S libwebsockets The following file will be downloaded: /gnu/store/1k4c1a6nckhm2hjpprvdrlkxx6yifclw-libwebsockets-1.3 @ build-started /gnu/store/8x0jgw0819l7aqi1k1f6i772skmwq1zq-libwebsockets-1.3.drv - x86_64-linux /var/log/guix/drvs/8x//0jgw0819l7aqi1k1f6i772skmwq1zq-libwebsockets-1.3.drv.bz2 Cloning into '/gnu/store/1k4c1a6nckhm2hjpprvdrlkxx6yifclw-libwebsockets-1.3'... C-c C-c $ sudo cat /var/guix/substitute-binary/cache/1k4c1a6nckhm2hjpprvdrlkxx6yifclw (narinfo (version 1) (cache-uri "http://hydra.gnu.org";) (date 1413466633) (value "StorePath:... --8<---------------cut here---------------end--------------->8--- Here, “The following file will be downloaded” means that a substitute is found and will be used, as seen also in the cache. But then we find ourselves performing the derivation locally regardless. Ludo’.
