Here we assume you’ve already made your first steps with Guix (veja Primeiros passos) and would like to get an overview about what’s going on under the hood.
When using Guix, each package ends up in the package store, in its own
directory—something that resembles /gnu/store/xxx-package-1.2,
xxx is a base32 string.
Instead of referring to these directories, users have their own
profile, which points to the packages that they actually want to use.
These profiles are stored within each user’s home directory, at
alice installs GCC 4.7.2. As a result,
/home/alice/.guix-profile/bin/gcc points to
/gnu/store/…-gcc-4.7.2/bin/gcc. Now, on the same machine,
bob had already installed GCC 4.8.0. The profile of
simply continues to point to
/gnu/store/…-gcc-4.8.0/bin/gcc—i.e., both versions of GCC
coexist on the same system without any interference.
guix package command is the central tool to manage packages
guix package). It operates on the per-user profiles, and
can be used with normal user privileges.
The command provides the obvious install, remove, and upgrade operations.
Each invocation is actually a transaction: either the specified
operation succeeds, or nothing happens. Thus, if the
process is terminated during the transaction, or if a power outage occurs
during the transaction, then the user’s profile remains in its previous
state, and remains usable.
In addition, any package transaction may be rolled back. So, if, for example, an upgrade installs a new version of a package that turns out to have a serious bug, users may roll back to the previous instance of their profile, which was known to work well. Similarly, the global system configuration on Guix is subject to transactional upgrades and roll-back (veja Usando o sistema de configuração).
All packages in the package store may be garbage-collected. Guix can
determine which packages are still referenced by user profiles, and remove
those that are provably no longer referenced (veja Invocando
Users may also explicitly remove old generations of their profile so that
the packages they refer to can be collected.
Guix takes a purely functional approach to package management, as described in the introduction (veja Introdução). Each /gnu/store package directory name contains a hash of all the inputs that were used to build that package—compiler, libraries, build scripts, etc. This direct correspondence allows users to make sure a given package installation matches the current state of their distribution. It also helps maximize build reproducibility: thanks to the isolated build environments that are used, a given build is likely to yield bit-identical files when performed on different machines (veja container).
This foundation allows Guix to support transparent binary/source
deployment. When a pre-built binary for a /gnu/store item is
available from an external source—a substitute, Guix just downloads
it and unpacks it; otherwise, it builds the package from source, locally
(veja Substitutos). Because build results are usually bit-for-bit
reproducible, users do not have to trust servers that provide substitutes:
they can force a local build and challenge providers (veja Invocando
Control over the build environment is a feature that is also useful for
guix shell command allows developers of a package
to quickly set up the right development environment for their package,
without having to manually install the dependencies of the package into
their profile (veja Invoking
All of Guix and its package definitions is version-controlled, and
guix pull allows you to “travel in time” on the history of Guix
itself (veja Invocando
guix pull). This makes it possible to replicate a
Guix instance on a different machine or at a later point in time, which in
turn allows you to replicate complete software environments, while
retaining precise provenance tracking of the software.