[Nix-dev] builder is root, not nixbld<n> [was: cannot build coreutils]

[Ben Franksen]

Hello

tl;dr I can verify with a very simple nix expression that the builder indeed 
is root, and not one of the nixbld users. I think this is not as it should 
be.

Any idea what I am doing wrong?

Details follow:

Here is the test expression:

{stdenv, coreutils}: stdenv.mkDerivation {
  name = "trivial-0.0";
  builder = ./builder.sh;
  inherit coreutils;
}

and the builder is just

$coreutils/bin/id

> nix-build '<nixpkgs>' -A trivial
these derivations will be built:
  /nix/store/11h7h69wfw56d4j4xgmpgwk2k2hccq6r-trivial-0.0.drv
building path(s) `/nix/store/jvqphwydc3p3ggsn5bmdwks0n5lppqwk-trivial-0.0'
uid=0(root) gid=0(root) groups=0(root)
[...]

When I give the -K option I can see that everything under /tmp/nix-... is 
owned by root.

I re-installed nix-1.7 from source and re-checked my configuration.

These are the build users:

> grep nixbld /etc/{passwd,group}
/etc/passwd:nixbld0:x:40000:40000:Nix build user 
0,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld1:x:40001:40000:Nix build user 
1,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld2:x:40002:40000:Nix build user 
2,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld3:x:40003:40000:Nix build user 
3,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld4:x:40004:40000:Nix build user 
4,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld5:x:40005:40000:Nix build user 
5,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld6:x:40006:40000:Nix build user 
6,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld7:x:40007:40000:Nix build user 
7,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld8:x:40008:40000:Nix build user 
8,,,:/var/run/empty:/bin/false
/etc/passwd:nixbld9:x:40009:40000:Nix build user 
9,,,:/var/run/empty:/bin/false
/etc/group:nixbld:x:40000:nixbld0,nixbld1,nixbld2,nixbld3,nixbld4,nixbld5,nixbld6,nixbld7,nixbld8,nixbld9

That looks ok to me. My /etc/nix/nix.conf contains one line

  build-users-group = nixbld

(I disabled chroot builds for the moment)

Environment:

 > env|grep NIX

NIX_REMOTE=daemon
NIX_PATH=nixpkgs=/home/ben/.nix-defexpr/channels/nixos-13.10/nixpkgs

For the multi-user setup I largely followed the instructions here:

http://sandervanderburg.blogspot.de/2013/06/setting-up-multi-user-nix-installation.html

except that I use this very simple upstart job for the nix-daemon:

# Nix build daemon.
description "Nix build daemon"
start on runlevel [2345]
stop on runlevel [!2345]
exec /usr/local/bin/nix-daemon

Cheers
Ben
-- 
"Make it so they have to reboot after every typo." -- Scott Adams