Add agetty service and null modem test

services-agnostic/agetty/default.nix

@@ -0,0 +1,14 @@
+{createManagedProcess, util-linux}:
+{port, instanceName ? "agetty-${port}", baudrate ? 9600, extraOptions ? []}:
+
+createManagedProcess {
+  inherit instanceName;
+  foregroundProcess = "${util-linux}/bin/agetty";
+  args = extraOptions ++ [ port baudrate ];
+
+  overrides = {
+    sysvinit = {
+      runlevels = [ 2 3 4 5 ];
+    };
+  };
+}

services-agnostic/constructors.nix

@@ -207,4 +207,9 @@ in
     inherit createManagedProcess forceDisableUserChange logDir libDir callingUser callingGroup;
     inherit (pkgs) stdenv vsftpd writeTextFile lib;
   };
+
+  agetty = import ./agetty {
+    inherit createManagedProcess;
+    inherit (pkgs) util-linux;
+  };
 }

tests/agetty/note.md

@@ -0,0 +1,9 @@
+This test is for setting up a connection with a null modem cable that works
+to link up my PC with my Commodore Amiga 500.
+
+It cannot be automated with the NixOS test driver, but you can manually deploy
+it by running the following command as root user:
+
+```bash
+nixproc-supervisord-deploy-stateless processes.nix
+```

tests/agetty/processes.nix

@@ -0,0 +1,28 @@
+{ pkgs ? import <nixpkgs> { inherit system; }
+, system ? builtins.currentSystem
+, stateDir ? "/var"
+, runtimeDir ? "${stateDir}/run"
+, logDir ? "${stateDir}/log"
+, spoolDir ? "${stateDir}/spool"
+, cacheDir ? "${stateDir}/cache"
+, libDir ? "${stateDir}/lib"
+, tmpDir ? (if stateDir == "/var" then "/tmp" else "${stateDir}/tmp")
+, forceDisableUserChange ? false
+, processManager
+, nix-processmgmt ? ../../../nix-processmgmt
+}:
+
+let
+  constructors = import ../../services-agnostic/constructors.nix {
+    inherit pkgs stateDir runtimeDir logDir tmpDir cacheDir libDir spoolDir forceDisableUserChange processManager nix-processmgmt;
+  };
+in
+{
+  agetty-nullmodem = {
+    pkg = constructors.agetty {
+      baudrate = 19200;
+      port = "ttyUSB0";
+      extraOptions = [ "--flow-control" ];
+    };
+  };
+}