ci.guix.gnu.org server is a front-end to an official
build farm that builds packages from Guix continuously for some
architectures, and makes them available as substitutes. This is the default
source of substitutes; it can be overridden by passing the
--substitute-urls option either to
guix-daemon --substitute-urls) or
to client tools such as
(see client --substitute-urls option).
Substitute URLs can be either HTTP or HTTPS. HTTPS is recommended because communications are encrypted; conversely, using HTTP makes all communications visible to an eavesdropper, who could use the information gathered to determine, for instance, whether your system has unpatched security vulnerabilities.
Substitutes from the official build farm are enabled by default when using Guix System (see GNU发行版). However, they are disabled by default when using Guix on a foreign distribution, unless you have explicitly enabled them via one of the recommended installation steps (see 安装). The following paragraphs describe how to enable or disable substitutes for the official build farm; the same procedure can also be used to enable substitutes for any other substitute server.