nixpkgs/doc/packages/etc-files.section.md

# /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`.
glibc: add dependency on netbase /etc/protocols Add an explicit dependency on netbase for /etc/protocols Certain functions in glibc look for files present in /etc such as getprotobyname which reads /etc/protocols. If you are using Nix over a Linux installation, this file may not be present, and therefore it will cause errors. - add netbase as a new package in nixpks - add a dependency in glibc on it using postPatchPhase and substitute the path Fixes #124401 2021-09-13 02:04:10 +00:00			`# /etc files {#etc}`

doc/builders: fix typos 2022-03-10 19:43:29 +00:00			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.
glibc: add dependency on netbase /etc/protocols Add an explicit dependency on netbase for /etc/protocols Certain functions in glibc look for files present in /etc such as getprotobyname which reads /etc/protocols. If you are using Nix over a Linux installation, this file may not be present, and therefore it will cause errors. - add netbase as a new package in nixpks - add a dependency in glibc on it using postPatchPhase and substitute the path Fixes #124401 2021-09-13 02:04:10 +00:00
doc/builders: fix typos 2022-03-10 19:43:29 +00:00			`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.`
glibc: add dependency on netbase /etc/protocols Add an explicit dependency on netbase for /etc/protocols Certain functions in glibc look for files present in /etc such as getprotobyname which reads /etc/protocols. If you are using Nix over a Linux installation, this file may not be present, and therefore it will cause errors. - add netbase as a new package in nixpks - add a dependency in glibc on it using postPatchPhase and substitute the path Fixes #124401 2021-09-13 02:04:10 +00:00
doc/builders: fix typos 2022-03-10 19:43:29 +00:00			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.
glibc: add dependency on netbase /etc/protocols Add an explicit dependency on netbase for /etc/protocols Certain functions in glibc look for files present in /etc such as getprotobyname which reads /etc/protocols. If you are using Nix over a Linux installation, this file may not be present, and therefore it will cause errors. - add netbase as a new package in nixpks - add a dependency in glibc on it using postPatchPhase and substitute the path Fixes #124401 2021-09-13 02:04:10 +00:00
nixpkgs/doc/glibc: better glibc link also replace unicode symbol in case some environment cannot reproduce the encoding or font symbol. 2021-09-22 18:28:58 +00:00
glibc: add dependency on netbase /etc/protocols Add an explicit dependency on netbase for /etc/protocols Certain functions in glibc look for files present in /etc such as getprotobyname which reads /etc/protocols. If you are using Nix over a Linux installation, this file may not be present, and therefore it will cause errors. - add netbase as a new package in nixpks - add a dependency in glibc on it using postPatchPhase and substitute the path Fixes #124401 2021-09-13 02:04:10 +00:00			```bash
nixpkgs/doc/glibc: better glibc link also replace unicode symbol in case some environment cannot reproduce the encoding or font symbol. 2021-09-22 18:28:58 +00:00			`> nix-shell -p iana-etc`
glibc: add dependency on netbase /etc/protocols Add an explicit dependency on netbase for /etc/protocols Certain functions in glibc look for files present in /etc such as getprotobyname which reads /etc/protocols. If you are using Nix over a Linux installation, this file may not be present, and therefore it will cause errors. - add netbase as a new package in nixpks - add a dependency in glibc on it using postPatchPhase and substitute the path Fixes #124401 2021-09-13 02:04:10 +00:00
			`[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`
			```

doc/builders: fix typos 2022-03-10 19:43:29 +00:00			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`.