Bug#877331: sponsorship-requests: nix/1.1.15 (ITP 877019) -- Purely functional package manager

[Kai Harries <kai.harries@gmail.com>]

Dmitry Bogatov <KAction@debian.org> writes:

> [2018-12-29 19:54] Vincent Bernat <bernat@debian.org>
>> > Probably not. Violations of FHS is violation of policy, and to get
>> > authorization to policy violation is long road, starting with discussion
>> > on debian-devel@.
>> >
>> > But, can't we just configure Nix to store it under /var/nix?
>> 
>> This would break the ability to use pre-built stuff and make nix
>> slow.
>
> I belive you, but just for my curiosity, what will break if we download
> substitute (nar, almost tar archive) and extract it not in /nix, but in
> /var/nix?

The depender will break if the dependency is not at the path where it
used to be at build-time (by default /nix/store/...). All software
deployed by nix contains the full path to its dependencies. And all
dependencies are available inside the nix-store. The idea is to rely on
nothing that is outside the nix-store. 

For example an ldd on bash looks like this:

$ ldd /nix/store/ij6wirzff9id7jr071p04w4nk6hksc3y-bash-interactive-4.4-p23/bin/bash
/nix/store/ij6wirzff9id7jr071p04w4nk6hksc3y-bash-interactive-4.4-p23/bin/bash:
        linux-vdso.so.1 (0x00007ffe1a7d5000)
        libreadline.so.7 => /nix/store/vvwxc17kpc39qbcz7qp7mkqa7fr0my84-readline-7.0p5/lib/libreadline.so.7 (0x00007f25b0593000)
        libhistory.so.7 => /nix/store/vvwxc17kpc39qbcz7qp7mkqa7fr0my84-readline-7.0p5/lib/libhistory.so.7 (0x00007f25b0389000)
        libncursesw.so.6 => /nix/store/2lbhgxlrhgnij2c3bm719xidymmhp0m0-ncurses-6.1-20181027/lib/libncursesw.so.6 (0x00007f25b011a000)
        libdl.so.2 => /nix/store/7gx4kiv5m0i7d7qkixq2cwzbr10lvxwc-glibc-2.27/lib/libdl.so.2 (0x00007f25aff16000)
        libc.so.6 => /nix/store/7gx4kiv5m0i7d7qkixq2cwzbr10lvxwc-glibc-2.27/lib/libc.so.6 (0x00007f25afb62000)
        /nix/store/7gx4kiv5m0i7d7qkixq2cobra10lvxwc-glibc-2.27/lib/ld-linux-x86-64.so.2 => /nix/store/7gx4kiv5m0i7d7qkixq2cwzbr10lvxwc-glibc-2.27/lib64/ld-linux-x86-64.so.2 (0x00007f25b07def000)

Regards, Kai