Command Shell

A shell is a program that translates text commands (like ls, vim, reboot etc) into instructions for your computer. The default shell on NixOS is bash, but it can be easily changed.

Note: Zsh is used here as an example. You can use other shells, e.g. Fish or Nushell.

Enable

When adding a new shell, always enable the shell system-wide, even if it's already enabled in your Home Manager configuration, otherwise it won't source the necessary files.

For example, for Zsh:

❄︎ /etc/nixos/configuration.nix

programs.zsh.enable = true;

Changing the default shell

For all users

To set a command shell as the default for all users, use the defaultUserShell option.

For example, to set Zsh as the default user shell for all users(including root):

❄︎ /etc/nixos/configuration.nix

users.defaultUserShell = pkgs.zsh;

For a specific user

To set a command shell as the default for a particular user, use the <name>.shell option.

For example, to set user "myuser"'s shell to fish:

❄︎ /etc/nixos/configuration.nix

users.users.myuser.shell = pkgs.fish;

You can also choose whether or not a user should use the default shell:

❄︎ /etc/nixos/configuration.nix

users.users.myuser.useDefaultShell = true;

Using a different shell in nix-shell and nix develop

By default, both nix develop and nix-shell launch an interactive bash shell. However, it is possible to configure these environments to use an alternative shell.

There are multiple approaches available:

nix-your-shell

Refer to nix-your-shell for installation and usage instructions.

any-nix-shell

Refer to any-nix-shell for installation and usage instructions.

Aliasing command

A simple, lightweight method is to alias the relevant commands to invoke the shell directly. For example:

≡︎ .bashrc

alias nix-shell='nix-shell --run zsh'
nix() {
  if [[ $1 == "develop" ]]; then
    shift
    command nix develop -c zsh "$@"
  else
    command nix "$@"
  fi
}

There are some caveats with this approach:

Nested shells will require you to type exit twice, once to leave the inner shell and once to exit the Nix shell environment itself.
Potential for alias conflicts as overriding commands can introduce unintended side effects in scripts or other tooling that expects the standard behavior.

Using Flakes

If you are using Flakes with fish, the 'command-not-found' error message will not work correctly, but can be fixed by disabling the builtin Nix command-not-found program:^[1]

❄︎ /etc/nixos/configuration.nix

programs.command-not-found.enable = false;