Crash is a highly efficient and user-configurable login shell wrapper designed for flexibility and ease of use. It allows users to specify a sequence of shell executables through the SHELLS environment variable, executing them in order and halting when one exits successfully (returning a 0 exit code).

Key Features

• Customizable User Shells: Empower users to configure their own shells without the need for superuser access. Set the SHELLS variable to custom paths, such as .config/shell, and enable users to change shell preferences easily.

• Hotswap Shells: Seamlessly switch between different shell environments while using SSH. This feature is particularly useful for multi-user scenarios on shared accounts, where different users might prefer different shell setups. Check out the "Tips & Tricks" section to enhance your SSH experience with Crash.

• Reliable Fallback Mechanism: Prevent potential lockouts by defining a fallback shell. If the preferred shell fails to launch, Crash will automatically revert to a predefined fallback shell, such as bashInteractive, making it perfect for users exploring new or unstable shells like Nushell.

Usage Overview

To implement Crash, simply load the repository into your inputs:

{
  inputs.crash.url = "github:RGBCube/crash";
}

Then, configure your desired shells in the NixOS module:

{
  environment.sessionVariables.SHELLS = "${lib.getExe pkgs.nushell}:${lib.getExe pkgs.fish}";
}

For users compiling without Nix, use the following command:

zig build --release=safe -Dcpu=baseline -Dfallback_shell=/bin/<yourshell>

Tips & Tricks

Maximize your workflow by controlling the default shell launched through SSH. Make OpenSSH recognize the SHELLS environment variable:

{
  services.openssh = {
    enable = true;
    settings.AcceptEnv = "SHELLS";
  };
}

Then configure your .ssh/config:

Host myvps
    SetEnv SHELLS=fish:nu:bash:dash

Common Issues

One common pitfall is using the tilde (~) for home directory references in the SHELLS variable. Remember, it won’t expand. Instead, use relative paths:

SHELLS=.config/shell # This WILL work!

Conclusion

Crash provides a powerful, flexible solution for managing your login shells, ensuring you maintain accessibility and ease of configuration without requiring elevated privileges. Whether you're managing a shared environment or exploring new shell options, Crash has you covered. Explore the repository to learn more about how you can enhance your shell experience!