Merge branch 'nixos-unstable-small' of https://github.com/NixOS/nixpkgs into HEAD

1 files changed, 18 insertions, 0 deletions

diff --git a/nixpkgs/doc/packages/etc-files.section.md b/nixpkgs/doc/packages/etc-files.section.md
new file mode 100644
index 000000000000..94a769ed3355
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+++ b/nixpkgs/doc/packages/etc-files.section.md
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+# /etc files {#etc}
+
+Certain calls in glibc require access to runtime files found in `/etc` such as `/etc/protocols` or `/etc/services` -- [getprotobyname](https://linux.die.net/man/3/getprotobyname) is one such function.
+
+On non-NixOS distributions these files are typically provided by packages (i.e., [netbase](https://packages.debian.org/sid/netbase)) if not already pre-installed in your distribution. This can cause non-reproducibility for code if they rely on these files being present.
+
+If [iana-etc](https://hydra.nixos.org/job/nixos/trunk-combined/nixpkgs.iana-etc.x86_64-linux) is part of your `buildInputs`, then it will set the environment variables `NIX_ETC_PROTOCOLS` and `NIX_ETC_SERVICES` to the corresponding files in the package through a setup hook.
+
+
+```bash
+> nix-shell -p iana-etc
+
+[nix-shell:~]$ env | grep NIX_ETC
+NIX_ETC_SERVICES=/nix/store/aj866hr8fad8flnggwdhrldm0g799ccz-iana-etc-20210225/etc/services
+NIX_ETC_PROTOCOLS=/nix/store/aj866hr8fad8flnggwdhrldm0g799ccz-iana-etc-20210225/etc/protocols
+```
+
+Nixpkg's version of [glibc](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/glibc/default.nix) has been patched to check for the existence of these environment variables. If the environment variables are *not* set, then it will attempt to find the files at the default location within `/etc`.