From 00c01658ff206195b06deb2337f91586b51a6901 Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Thu, 5 Sep 2019 09:31:44 -0400
Subject: [PATCH] Add a module for configuring a 100TB system
---
nixos/modules/100tb.nix | 131 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 131 insertions(+)
create mode 100644 nixos/modules/100tb.nix
diff --git a/nixos/modules/100tb.nix b/nixos/modules/100tb.nix
new file mode 100644
index 00000000..243da0dd
--- /dev/null
+++ b/nixos/modules/100tb.nix
@@ -0,0 +1,131 @@
+# A NixOS module which configures a system that is hosted by 100TB. Each of
+# our servers hosted with 100TB will probably import this module and pass it
+# the minimum system configuration to get the server to boot and accept
+# administrative ssh connections.
+#
+# A NixOS module is defined as a Nix expression language function.
+{
+ # This contains generally useful library functionality provided by nixpkgs.
+ # These are things like string manipulation and, notably for us, a library
+ # for defining options for configuring moduless.
+ lib,
+
+ # This is all of the configuration for a particular system where this module
+ # might be instantiated. For any system where we want the 100TB module to
+ # be active, this should have the 100TB configuration details (IP, gateway,
+ # etc).
+ config,
+
+ # More parameters exist and are accepted but we don't need them so we ignore them.
+ ...
+}:
+let
+ # Pull out the configuration for this module for convenient use later. The
+ # module name is quoted because `1` makes `100tb` look an awful lot like it
+ # should be a number.
+ cfg = config."100tb".config;
+
+ # Define the API to this module. Everything in `options` is about
+ # specifying what kind of values we expect to be given. This is both
+ # human-facing documentation as well as guidance to NixOS about acceptable
+ # values (mainly by type) so it can automatically reject certain bogus
+ # values. This value is in the `let` to make the code below a little easier
+ # to read. See below where we use it.
+ options = {
+ interface = lib.mkOption
+ { type = lib.types.str;
+ example = lib.literalExample "eno0";
+ description = "The name of the network interface on which to configure a static address.";
+
+ };
+ publicIPv4 = lib.mkOption
+ { type = lib.types.str;
+ example = lib.literalExample "192.0.2.0";
+ description = "The IPv4 address to statically assign to `interface`.";
+ };
+ prefixLength = lib.mkOption
+ { type = lib.types.int;
+ example = lib.literalExample 24;
+ description = "The statically configured network's prefix length.";
+ };
+ gateway = lib.mkOption
+ { type = lib.types.str;
+ example = lib.literalExample "192.0.2.1";
+ description = "The statically configured address of the network gateway.";
+ };
+ gatewayInterface = lib.mkOption
+ { type = lib.types.str;
+ example = lib.literalExample "eno0";
+ description = "The name of the network interface for the default route.";
+ default = cfg.interface;
+ };
+ grubDeviceID = lib.mkOption
+ { type = lib.types.str;
+ example = lib.literalExample "wwn-0x5000c500936410b9";
+ description = "The ID of the disk on which to install grub.";
+ };
+ rootPublicKey = lib.mkOption
+ { type = lib.types.str;
+ example = lib.literalExample "ssh-ed25519 AAAA... username@host";
+ description = "The public key to install for the root user.";
+ };
+ };
+in {
+ # Here we actually define the module's options. They're what we said they
+ # were above, all bundled up into a "submodule" which is really just a set
+ # of options.
+ options =
+ { "100tb".config = lib.mkOption
+ { type = lib.types.submodule { inherit options; };
+ description = "Host-specific configuration relevant to a 100TB system.";
+ };
+ };
+
+ # Now compute the configuration that results from whatever values were
+ # supplied for our options. A lot of this is currently very similar to
+ # what's in bootstrap-configuration.nix (which is well commented). The
+ # similarity makes sense - both that configuration and this one need to get
+ # a 100TB machine to boot and let an admin SSH in.
+ #
+ # Values that go into `config` here are merged into values that go into
+ # `config` in any other active modules. Basically, everything in this
+ # `config` is treated as if it were in the configuration set defined by
+ # `/etc/nixos/configuration.nix`. The module just gives us a way to factor
+ # separate concerns separately and make reuse easier.
+ #
+ # Note that this is not where Tahoe-LAFS configuration goes. It's just
+ # about getting base platform into good shape.
+ #
+ # Perhaps at some point this can be refactored to remove the duplication.
+ # It's slightly tricky because we don't want to introduce any external
+ # dependencies to bootstrap-configuration.nix because that would make it
+ # harder to deploy in the bootstrap environment.
+ config =
+ { boot.loader.grub.enable = true;
+ boot.loader.grub.version = 2;
+ boot.loader.grub.device = "/dev/disk/by-id/${cfg.grubDeviceID}";
+
+ boot.loader.timeout = 1;
+ networking.firewall.enable = false;
+ services.openssh.enable = true;
+
+ users.users.root.openssh.authorizedKeys.keys = [
+ cfg.rootPublicKey
+ ];
+
+ networking.dhcpcd.enable = false;
+ networking.interfaces = {
+ "${cfg.interface}".ipv4.addresses = [
+ { address = cfg.publicIPv4; inherit (cfg) prefixLength; }
+ ];
+ };
+ networking.defaultGateway = {
+ address = cfg.gateway;
+ interface = cfg.gatewayInterface;
+ };
+ networking.nameservers = [
+ "4.2.2.1"
+ "8.8.8.8"
+ ];
+ };
+}
--
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