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README.md

@@ -1,10 +1,78 @@
 # Colmena
 
-Colmena is a simple, stateless NixOS deployment tool modeled after NixOps and Morph, written in Rust.
+Colmena is a simple, stateless NixOS deployment tool modeled after [NixOps](https://github.com/NixOS/nixops) and [Morph](https://github.com/DBCDK/morph), written in Rust.
 It's a thin wrapper over Nix commands like `nix-instantiate` and `nix-copy-closure`, and supports parallel deployment.
 
 Colmena is still an early prototype.
 
+## Tutorial
+
+Enter a `nix-shell` with `colmena` with:
+```
+nix-shell test-shell.nix
+```
+
+Colmena should work with your existing NixOps and Morph configurations with minimal modification.
+Here is a sample `hive.nix` with two nodes, with some common configurations applied to both nodes:
+
+```nix
+{
+  network = {
+    # Override to pin the Nixpkgs version (recommended). This option
+    # accepts one of the following:
+    # - A path to a Nixpkgs checkout
+    # - The Nixpkgs lambda (e.g., import <nixpkgs>)
+    # - An initialized Nixpkgs attribute set
+    nixpkgs = <nixpkgs>;
+  };
+
+  defaults = { pkgs, ... }: {
+    # This module will be imported by all hosts
+    environment.systemPackages = with pkgs; [
+      vim wget curl
+    ];
+  };
+
+  host-a = { name, nodes, ... }: {
+    # The name and nodes parameters are supported in Colmena,
+    # allowing you to reference configurations in other nodes.
+    networking.hostName = name;
+    time.timeZone = nodes.host-b.config.time.timeZone;
+
+    boot.loader.grub.device = "/dev/sda";
+    fileSystems."/" = {
+      device = "/dev/sda1";
+      fsType = "ext4";
+    };
+  };
+
+  host-b = {
+    # Like NixOps and Morph, Colmena will attempt to connect to
+    # the remote host using the attribute name by default. You
+    # can override it like:
+    deployment.targetHost = "host-b.mydomain.tld";
+
+    time.timeZone = "America/Los_Angeles";
+
+    boot.loader.grub.device = "/dev/sda";
+    fileSystems."/" = {
+      device = "/dev/sda1";
+      fsType = "ext4";
+    };
+  };
+}
+```
+
+The full set of options can be found at `src/eval.nix`.
+Run `colmena build` in the same directory to build the configuration, or do `colmena apply` to deploy it to all nodes.
+
+## Current limitations
+
+- It's required to use SSH keys to log into the remote hosts, and interactive authentication will not work.
+- There is no option to override SSH or `nix-copy-closure` options.
+- Node tagging is not yet implemented.
+- Error reporting is lacking.
+
 ## Licensing
 
 Colmena is available under the MIT License.