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glibc: Fix _CS_PATH to include default profile #94937

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glibc: Fix _CS_PATH to include default profile #94937

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McDutchie
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@McDutchie McDutchie commented Aug 8, 2020 •
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Motivation for this change

The string returned by confstr(_CS_PATH), which is also the output of the command getconf PATH, contains a default path that is guaranteed to find (at least) all POSIX standard utilities. The current value is:

/run/current-system/sw/bin:/bin:/usr/bin

There are two problems with this.

  1. /bin and /usr/bin should be removed, as NixOS package management never puts anything there. Anything dropped in /bin or /usr/bin under the name of a standard utility would likely be bogus.

  2. The default profile binaries directory is not in it. This is a problem because the default NixOS installation lacks several mandatory standard POSIX utilities. The command recommended by the system's error message for a missing command to install a missing package foo is nix-env -iA nixos.foo. When this is done as root, the corresponding binaries are installed for all users in /nix/var/nix/profiles/default/bin.

Things done

pkgs/development/libraries/glibc/fix_path_attribute_in_getconf.patch:

  • CS_PATH: Replace /bin:/usr/bin fallback by default profile path /nix/var/nix/profiles/default/bin.

Fixes: #65512

@McDutchie
glibc: Fix _CS_PATH to include default profile
cc3b34a 
The string returned by confstr(_CS_PATH)[*1], which is also the
output of the command 'getconf PATH'[*2], contains a default path
that is guaranteed to find (at least) all POSIX standard utilities.
The current value is:

    /run/current-system/sw/bin:/bin:/usr/bin

There are two problems with this.

1. /bin and /usr/bin should be removed, as NixOS package management
   never puts anything there. Anything dropped in /bin or /usr/bin
   under the name of a standard utility would likely be bogus.

2. The default profile binaries directory is not in it. This is a
   problem because the default NixOS installation lacks several
   mandatory standard POSIX utilities. The command recommended by
   the system's error message for a missing command to install a
   missing package foo is 'nix-env -iA nixos.foo'. When this is
   done as root, the corresponding binaries are installed for all
   users in /nix/var/nix/profiles/default/bin.

This commit fixes these problems as follows:

pkgs/development/libraries/glibc/fix_path_attribute_in_getconf.patch:
- CS_PATH: Replace '/bin:/usr/bin' fallback by default profile path
  '/nix/var/nix/profiles/default/bin'.

[*1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/confstr.html
[*2] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/getconf.html

Fixes: NixOS#65512
@McDutchie
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Could someone rerun the ofborg check? Not sure what it does, but the results indicate it timed out before running anything, so that's not a problem with the PR.

@McDutchie
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Ping @peti (who committed the original value).

@SuperSandro2000
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@ofborg eval

@McDutchie McDutchie mentioned this pull request Jun 19, 2021
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stale bot commented Jun 28, 2021

I marked this as stale due to inactivity. → More info

@stale stale bot added the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jun 28, 2021
@McDutchie
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Again, still not stale. See #65512

@stale stale bot removed the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jun 29, 2021
@lheckemann
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I'm not sure if /bin and /usr/bin should be removed, due to /bin/sh and /usr/bin/env?

@McDutchie
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I'm not sure if /bin and /usr/bin should be removed, due to /bin/sh and /usr/bin/env?

/bin and /usr/bin are unused in NixOS. Those compatibility symlinks are for invoking /bin/sh and /usr/bin/env directly, without searching $PATH, so they're not relevant for a default $PATH search. Their real binaries are in /run/current-system/sw/bin.

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stale bot commented Jan 3, 2022

I marked this as stale due to inactivity. → More info

@stale stale bot added the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jan 3, 2022
@McDutchie
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McDutchie commented Jan 3, 2022 •
edited

Yet again, not stale.

@stale stale bot removed the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jan 3, 2022
@SuperSandro2000
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/bin and /usr/bin are unused in NixOS.

but not when nixpkgs is used in another Distro. I think it is save to add the new entry but not to remove the default entries.

Yet again, not stale.

It didn't get any attention in the last 6 months which is stale. That does not mean it is irrelevant.

@McDutchie
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/bin and /usr/bin are unused in NixOS.

but not when nixpkgs is used in another Distro. I think it is save to add the new entry but not to remove the default entries.

Surely another distro that uses nixpkgs would use their own libc and not NixOS's version of glibc.

Besides, you cannot know for sure what the correct default directories on any other OS are.

@SuperSandro2000
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Surely another distro that uses nixpkgs would use their own libc and not NixOS's version of glibc.

Nope, everything is linked against the libc in nixpkgs.

Besides, you cannot know for sure what the correct default directories on any other OS are.

But /bin:/usr/bin is a pretty good guess which works 99% of the time and removing it from the defaults is bound to break things for people that use nixpkgs on none nixos like me.

@stale stale bot added the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jul 31, 2022
@Et7f3
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Et7f3 commented Jan 24, 2023

Non nix-managed tools would most likely be linked agains an external libc.

Do we have a way to query os ? I see stdenv.isCygwin, stdenv.isMips, stdenv.isSunOS but no stdenv.isNixOS.

Maybe add this variable in another PR and use it so on non nixos ok we keep impure path but on nixos we can safely remove them.

@stale stale bot removed the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Jan 24, 2023
@wegank wegank added the 2.status: stale https://github.com/NixOS/nixpkgs/blob/master/.github/STALE-BOT.md label Mar 19, 2024
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glibc: _CS_PATH aka $(getconf PATH) should end in default profile directory
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@McDutchie @SuperSandro2000 @lheckemann @Et7f3 @wegank @Janik-Haag