'nix-channel --update' stopped working on nix-2.2.1: error: while setting up the build environment: getting attributes of path '': No such file or directory

[trofi]

The install is a nix install on Gentoo (not a NixOS).

$ nix-channel --update --verbose
downloading 'https://nixos.org/channels/nixpkgs-unstable'...
downloading 'https://releases.nixos.org/nixpkgs/nixpkgs-19.03pre168678.54dcb0b1376/binary-cache-url'...
unpacking channels...
warning: Nix search path entry '/nix/var/nix/profiles/per-user/root/channels' does not exist, ignoring
error: while setting up the build environment: getting attributes of path '': No such file or directory
error: program '/usr/bin/nix-env' failed with exit code 1

I tried strace-ing nix-env and running nix-daemon but I did not find where that '' path comes from. Can nix be improved to dump more information on where that path comes from?

Some version info:

$ nix --version
nix (Nix) 2.2.1
$ nix-channel --list
nixpkgs https://nixos.org/channels/nixpkgs-unstable

ottidmes on #nixos linked me to a thread about /bin/sh out of nix: https://logs.nix.samueldr.com/nixos/2019-02-06#1938291

Working workaround:

$ nix-build '<nixpkgs>' -A bash
$ sudo systemctl restart nix-daemon

[trofi]

Found out today it was not completely working workaround. I got to the failure:

I built nix from source and did not pass --with-sandbox-shell=... option to ./configure. Unfortunately instead of bailing out nix built the following sandbox path:

$ nix show-config | fgrep sandbox
...
sandbox-paths = /bin/sh=

I worked around it locally by passing --with-sandbox-shell=/bin/busybox to ./configure.

To make problem harder to encounter I suggest to:

1. fail ./configure if --with-sandbox-shell= is not passed or default to /bin/sh
2. mention 'source' part fo sandbox-path when mounting onto target fails

Thanks!

[dtzWill]

fail ./configure if --with-sandbox-shell= is not passed or default to /bin/sh

This certainly seems in the territory of nix doctor if build-time check isn't preferred for whatever reason.
Truth is that in common usage Nix builders kinda really expect a /bin/sh to exist and probably have sane behavior in basic cases :).

Offhand 2) just seems like an omission---likely because it doesn't happen very often. Anyway, mentioning source sounds great, good idea!

[pmiddend]

Note that the Gentoo ebuild still seems to be broken. When updating, I get this error:

while setting up the build environment: executing '/bin/bash': No such file or directory
builder for '/nix/store/4birxpr75haj1mpw81ix5bw78lyj273r-nixpkgs-19.09pre174594.0c0954781e2.drv' failed with exit code 1
error: build of '/nix/store/4birxpr75haj1mpw81ix5bw78lyj273r-nixpkgs-19.09pre174594.0c0954781e2.drv' failed
error: program '/usr/bin/nix-env' failed with exit code 100

[trofi]

Please report it to http://bugs.gentoo.org/ and we'll try to sort out your problem.

[renatoGarcia]

I'm having this same problem on ArchLinux with nix 2.2.2, and at least one more person it's having it too (https://aur.archlinux.org/packages/nix/#comment-690619).
At first the path was empty:

$ nix show-config | grep sandbox
...
sandbox-paths = /bin/sh=

Then I have recompiled it with each of:

--with-sandbox-shell=/bin/sh
--with-sandbox-shell=/bin/bash
--with-sandbox-shell=/bin/busybox
--with-sandbox-shell=/nix/store/r7gk5w5i5qq4j44aazl4dbmvjn5p8v1c-busybox-1.29.2/bin/busybox
--with-sandbox-shell=/nix/store/6v88ick1cxnn5g91m8qrrqww0lrlr27x-bash-4.4-p23/bin/bash

With the last option, for instance the error is now:

nix-channel --update
unpacking channels...
while setting up the build environment: executing '/usr/bin/bash': No such file or directory
builder for '/nix/store/x2nwwcsq3z1czh1kw2r83pl5ihbh6c54-nixpkgs-19.03.172361.cf3e277dd0b.drv' failed with exit code 1
error: build of '/nix/store/x2nwwcsq3z1czh1kw2r83pl5ihbh6c54-nixpkgs-19.03.172361.cf3e277dd0b.drv' failed
error: program '/usr/bin/nix-env' failed with exit code 100

[renatoGarcia]

Removing the Arch package, the previous /nix, and installing through curl https://nixos.org/nix/install | sh I was able to get a working nix again.
I have not solved the problem, but I'm able to work on nix again for now.

[asppsa]

@renatoGarcia, I've fixed the Nix package in Arch Linux now by adding a bit of complex build-sandbox-paths = ... logic.

For others who are trying to work this out, the full set of scripts that you might need are listed in .../share/nix/corepkgs/config.nix (where ... is /usr for me). You need versions of all of these (including a number of coreutils packages: I think just env, mkdir and mv) that are either statically linked, or are installed from Nix. I've gone for the latter approach using a script to download the necessary packages from the most recent NixOS release.

I also tried to use busybox, but it seems that shell provided by busybox is not full-featured enough.

[edolstra]

This problem should go away once #2748 is merged. It makes nix-channel use a built-in derivation that doesn't require any additional paths in the sandbox.

[drewboardman]

I'm still seeing this issue, or similar:

https://github.com/NixOS/nixpkgs/issues/78714

[stale]

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