nix-env doesn't auto-create per-user profile?

[wmertens]

If your nix-env was originally set up by https://github.com/NixOS/nix/blob/master/scripts/nix-profile.sh.in#L5-L9 then your ~/.nix-profile will point to /nix/var/nix/profiles/default.

If you then use nix-env -i ... and you don't have write access to that directory, it will fail to update your environment instead of creating a new environment under /nix/var/nix/profiles/per-user/$USER/.

It will also not give you any indication of what's happening, all you get is error: opening lock file ‘/nix/var/nix/profiles/default.lock’: Permission denied

Is this expected behavior? If so, what would be the best way to improve the error message?

[wmertens]

I think it would make most sense if nix-env checked for a writeable profile and if not gave an error message like You need to have a writeable profile, run <xxx> to set it up.

[wmertens]

@edolstra any thoughts on this? Would you accept a PR as described above?

[kirelagin]

It would be totally nice to have a more verbose error message as suggested.
Also is it possible to create this default profile from the installation script / make install?

[benley]

The way NixOS handles it is to create the profile directory from the system login script. Compare the nix-profile.sh linked above (which is the one from the deb) with this bit of the nixos shell module: https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/programs/shell.nix#L23-L62

It handles non-root users rather differently. It seems to me that the deb setup is incorrect except in the case of single-user nix installs - which is what the packages claim to support, after all.

On my ubuntu systems I've replaced /etc/profile.d/nix.sh with a tweaked version that seems to be working well for me: https://gist.github.com/benley/e4a91e8425993e7d6668

[wmertens]

@benley thanks for the pointers, I made a PR for a better nix-only version.

[robinbb]

+1

[bgamari]

The error in the case that a user lacks a writeable profile is still awful:

error: opening lock file '/nix/var/nix/profiles/default.lock': Permission denied

It would be great if this could be a bit more descriptive, as suggested by @wmertens.

[markasoftware]

I just installed NixOS 18.04, upgraded to 19.03, then added a user via users.users in configuration.nix. They had no .nix-profile and nix-env -iA nixos.hello didn't automatically create it.

[mbrgm]

@markasoftware Were you able to fix this?

[markasoftware]

@mbrgm Yes, actually, although I can't guarantee my problem was the same as yours! I discovered that the problem was in how I was switching users. After adding the new user to configuration.nix and running nixos-rebuild switch, I was switching to the user by running su my-user-name. However, the correct form is su - my-user-name. I had always thought the - was just to protect against usernames that looked like options, but it actually changes the behavior of su substantially and makes it set certain important environment variables which nixos-env needs to operate correctly.