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diff --git a/example/flake.nix b/example/flake.nix
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+{
+  description = "Example of a Flake using flaky-utils.";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.05";
+    flake-utils.url = "github:numtide/flake-utils";
+    flaky-utils.url = "git+https://cgit.pacien.net/libs/flaky-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, flaky-utils }:
+  flake-utils.lib.eachDefaultSystem (system: let
+    pkgs = import nixpkgs { inherit system; };
+  in pkgs.lib.fold pkgs.lib.recursiveUpdate { } [
+
+    {
+      # Convenience development shell providing some tools.
+      #
+      # The binaries made available and the environment variable set are
+      # printed when entering the shell.
+      #
+      # The user's default shell is used instead of Bash (sacrifying a bit of
+      # reproducibility for convenience).
+      #
+      devShell = flaky-utils.lib.mkDevShell {
+        inherit pkgs;
+
+        tools = with pkgs; [
+          postgresql_14
+          pgcli
+        ];
+
+        envVars = rec {
+          PGDATA = "$PWD/development_database/pgdata";
+          PGHOST = "$PWD/development_database";
+          PGPORT = "5432";
+          PGDATABASE = "app";
+          DATABASE_URL = "postgresql:///${PGDATABASE}?host=${PGHOST}";
+        };
+
+        shell = null;
+      };
+    }
+
+    # Convenience isolated environment using a QEMU virtual machine.
+    #
+    # This defines a triplet of nixosConfiguration, package and app with the
+    # given name, so that the virtual machine can be launched using
+    # a command like `nix run .#sandbox`.
+    #
+    # By default, the VM is launched in the current console without a graphical
+    # interface, dropping to a shell for the default dummy user within.
+    #
+    # The current working directory from which the Flake is run is mounted and
+    # made available within the virtual machine in /mnt. The root filesystem
+    # is ephemeral (written to a temporary file in /tmp).
+    #
+    # The virtual machine's network is isolated by default: it cannot access
+    # the Internet nor the host's local network. Ports may nevertheless be
+    # forwarded explicitly from host to guest and vice-versa.
+    #
+    (flaky-utils.lib.mkSandboxSystem {
+      inherit nixpkgs system;
+
+      name = "sandbox";
+      user = "dummy";
+
+      config = {
+        virtualisation.forwardPorts = [
+          { from = "host"; host.port = 5432; guest.port = 5432; }  # postgres
+        ];
+
+        services.postgresql = {
+          enable = true;
+          enableTCPIP = true;
+
+          authentication = ''
+            host all all 0.0.0.0/0 trust
+          '';
+
+          initialScript = pkgs.writeText "init.sql" ''
+            create role dummy login superuser;
+          '';
+        };
+      };
+    })
+
+  ]);
+}