GNU Guix launches
Posted Nov 27, 2012 15:17 UTC (Tue) by lambda
In reply to: GNU Guix launches
Parent article: GNU Guix launches
Your objections seem to be based on not understanding the Nix package manager. If a user installs a package under Nix, it's installed in its own environment, and does not affect what packages other users see or behavior of other packages.
I guess that's what you call "containers (AKA VM-lite)", but it's not really the same thing; in fact, I would say both of those characterizations are wrong. A container isn't really "VM-lite", unless you want to call a modern operating system with separate users, memory protection, and preemptive multitasking "VM-lite" as well. A container is a way in which you can selectively isolate more resources, while sharing resources that still ought to be shared; it's the continuation of the idea of separate processes and memory protection, allowing you to apply isolation to more resources.
And Nix differs from a container, since in a container, you either give the user their own root with nothing shared, in which case, from a filesystem perspective, sure, it's VM-lite; everyone has to install all of their own copies of everything. Or you could share certain directories like /usr, but then you wind up with problems updating the base system breaking your packages installed in your container.
Nix works by building up a tree of package dependencies. Each package specifies the exact packages it depends on (the precise version and dependency tree, similar to the way Git refers commits by the SHA-1 of the current state and the SHA-1 of its ancestors), and packages are never replaced, new versions are installed in a new location. So a user can install local packages which depend on system packages, only using the extra space for what they specifically need; but if the base system updates, their packages will still depend on the old versions, causing them to stay around. Once the user updates their packages to newer version, depending on the new system libraries, the old versions will be GCed if no one depends on them.
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