ZSH as login shell in NixOs

Zsh, especially improved with OhMyZSH, is a great shell to work with. In NixOs, the default shell is bash, and everything is confired to work with it.

In particular, using zsh, one can unconter some difficulties such as the following:

$ rsync -rv nixbox:some/dir/ . 
zsh:1: command not found: rsync
rsync: connection unexpectedly closed (0 bytes received so far) [Receiver]
rsync error: remote command not found (code 127) at io.c(226) [Receiver=3.1.1]

This is because the environment is not completely set when the shell tried to launch a command just after the ssh connection is opened:

$ ssh nixbox 'echo $PATH'
/usr/bin:/bin:/usr/sbin:/sbin:/nix/store/…-openssh-…/bin
$ ssh nixbox 'source /etc/profile && echo $PATH'
/home/foo/bin:/var/setuid-wrappers:/home/foo/.nix-profile/bin:/home/foo/.nix-profile/sbin:…

Fortunately, nixos provide a conviniant and declarative way to properly configure zsh. To do so, one have to update his /etc/nix/configuration.nix file and make sure it contains something similar to the following:

{ config, pkgsk ... }:
{
  environment = {
    systemPackages = [ pkgs.zsh ];
    etc."zshenv".text =
      ''
      if [ -z "$__ETC_PROFILE_DONE" ]
      then
        . /etc/profile
      fi
      '';
    shells =
      [ "/run/current-system/sw/bin/zsh"
        "/var/run/current-system/sw/bin/zsh"
      ];
  };

  users.extraUsers.foo = {
    …
    shell = "/run/current-system/sw/bin/zsh";
    …
  };
}