I remember reading that nix unlike all other distros can install multiple version of the same package and I want this feature, but I guess programming a package config might be too much for me. Maybe I'll try nix package manager then.
You can browse some here: https://search.nixos.org/options
For example, to install an OpenSSH server and run it, you'd write:
services.openssh.enable = true;
services.openssh.ports = [
22
2222
];
environment.systemPackages = [
pkgs.firefox
pkgs.jq
];
(For NixOS, the Nix you write only starts looking like real code when you want to add new features or some packages to NixOS.)
The above is sometimes true and sometimes not. For the most part, Nix can install multiple versions of a program but only one can be in use at any given time.
Nix is for the most part shell based workflow (as in bash, zsh, etc.). The `nix-shell` command lets you switch out the packages (and versions of packages) that are used in any given shell, but it works off of a configuration file written in the Nix language that you write. The programs that are available are controlled by environment variables such as PATH and MANPATH.
Nix is a big shift from the usual way of dealing with packages, programs, etc. It isn't really useful until you really make the effort to understand what is going on, learn the Nix language, etc. If you are not interested in "programming" your system, then it probably isn't for you.
That’s not really true and is only a limitation of how PATH works on UNIXes (the first match is used). But you can for example add an aliased name for multiple versions of the same package, or for another meaning of use you can have different executables in the same environment different versions of the same lib (e.g. one bash script references python3, the other python3-at-specific-patch/minor-version/whatever)
That's a bit hand-wavey. More precisely: when you run a command, like `python3`, you can only associate that with one file. If you want multiple Python 3 interpreters, you'll have to use different names (e.g. making symlinks).
Alternatively, you don't need to bother "installing" anything; e.g. I use Nix for projects which use Scala, Maven, Python, NodeJS, etc. yet I don't have any of those installed. Instead, each project includes a `shell.nix` file which specifies the tools it wants. Running `nix-shell` in different folders gives me access to different tools.
Also, with Nix we only need to care about the end result: we can "install" a bunch of different programs, even if they have incompatible dependencies, since we're not "installing" those dependencies. ("Install" just means putting a symlink in some bin/ folder, like /run/current-system/sw/bin on NixOS or $HOME/.nix-profile/bin on non-NixOS)
I still encourage you to give it a try. You can build different versions of same package and not "install" them. Instead just execute the binary from the built version (I do this where I have a built-but-not-installed version of openssh-8.6 laying around because I have an old service that modern SSH no longer supports).
You can also run `nix-shell -p <custom-package-version>` to get a shell with a specific package available in the path, overtop of whatever might be globally installed.
Who knows, you might even be tempted to dip your toes into the Nix language by writing a custom `shell.nix` to build a shell with some more complex development environment, or to simply automate a complex `nix-shell -p` command.