From fb2fa1b50fe32e4d4f4e251b5892598f38f40a71 Mon Sep 17 00:00:00 2001
From: Alyssa Ross <hi@alyssa.is>
Date: Tue, 5 Apr 2022 10:03:25 +0000
Subject: [PATCH 1/2] nixos/postfix: pull setup into its own unit

Consider a service that generates postfix lookup tables with
postmap(1), like Mailman.  It needs the Postfix configuration file to
exist, but Postfix qmgr needs all the lookup tables its configured
with to exist before it starts.  So the service that runs postmap
needs to run after the Postfix configuration and directory structure
is generated, but before Postfix itself is started.  To enable this,
we split Postfix into two units: a oneshot unit that sets up the
configuration, and a longrun unit that supervises the Postfix
daemons.  The postmap services can then be inserted in between these
two units.
---
 nixos/modules/services/mail/mailman.nix |  3 +-
 nixos/modules/services/mail/postfix.nix | 39 ++++++++++++++-----------
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/nixos/modules/services/mail/mailman.nix b/nixos/modules/services/mail/mailman.nix
index 0c9b38b44b24..f36abadf9d77 100644
--- a/nixos/modules/services/mail/mailman.nix
+++ b/nixos/modules/services/mail/mailman.nix
@@ -313,7 +313,8 @@ in {
     systemd.services = {
       mailman = {
         description = "GNU Mailman Master Process";
-        after = [ "network.target" ];
+        after = [ "network.target" ]
+          ++ lib.optional cfg.enablePostfix "postfix-setup.service";
         restartTriggers = [ config.environment.etc."mailman.cfg".source ];
         wantedBy = [ "multi-user.target" ];
         serviceConfig = {
diff --git a/nixos/modules/services/mail/postfix.nix b/nixos/modules/services/mail/postfix.nix
index 23d3574ae27c..da14b6eef7ed 100644
--- a/nixos/modules/services/mail/postfix.nix
+++ b/nixos/modules/services/mail/postfix.nix
@@ -723,23 +723,10 @@ in
         { ${setgidGroup}.gid = config.ids.gids.postdrop;
         };
 
-      systemd.services.postfix =
-        { description = "Postfix mail server";
-
-          wantedBy = [ "multi-user.target" ];
-          after = [ "network.target" ];
-          path = [ pkgs.postfix ];
-
-          serviceConfig = {
-            Type = "forking";
-            Restart = "always";
-            PIDFile = "/var/lib/postfix/queue/pid/master.pid";
-            ExecStart = "${pkgs.postfix}/bin/postfix start";
-            ExecStop = "${pkgs.postfix}/bin/postfix stop";
-            ExecReload = "${pkgs.postfix}/bin/postfix reload";
-          };
-
-          preStart = ''
+      systemd.services.postfix-setup =
+        { description = "Setup for Postfix mail server";
+          serviceConfig.Type = "oneshot";
+          script = ''
             # Backwards compatibility
             if [ ! -d /var/lib/postfix ] && [ -d /var/postfix ]; then
               mkdir -p /var/lib
@@ -777,6 +764,24 @@ in
           '';
         };
 
+      systemd.services.postfix =
+        { description = "Postfix mail server";
+
+          wantedBy = [ "multi-user.target" ];
+          after = [ "network.target" "postfix-setup.service" ];
+          requires = [ "postfix-setup.service" ];
+          path = [ pkgs.postfix ];
+
+          serviceConfig = {
+            Type = "forking";
+            Restart = "always";
+            PIDFile = "/var/lib/postfix/queue/pid/master.pid";
+            ExecStart = "${pkgs.postfix}/bin/postfix start";
+            ExecStop = "${pkgs.postfix}/bin/postfix stop";
+            ExecReload = "${pkgs.postfix}/bin/postfix reload";
+          };
+        };
+
       services.postfix.config = (mapAttrs (_: v: mkDefault v) {
         compatibility_level  = pkgs.postfix.version;
         mail_owner           = cfg.user;

From 572131c6a945069dba5a12a0354df8254224a458 Mon Sep 17 00:00:00 2001
From: Alyssa Ross <hi@alyssa.is>
Date: Tue, 5 Apr 2022 10:10:51 +0000
Subject: [PATCH 2/2] nixos/mailman: ensure Postfix is started after Mailman

On first run, Postfix will refuse to start if it's started before
Mailman is up, because it'll try to read the map files generated
Mailman the first time it's started, and they won't exist yet.  To fix
this, make sure Postfix isn't started until after Mailman is up if
they're both activated at the same time.
---
 nixos/modules/services/mail/mailman.nix | 1 +
 1 file changed, 1 insertion(+)

diff --git a/nixos/modules/services/mail/mailman.nix b/nixos/modules/services/mail/mailman.nix
index f36abadf9d77..eee413df56da 100644
--- a/nixos/modules/services/mail/mailman.nix
+++ b/nixos/modules/services/mail/mailman.nix
@@ -313,6 +313,7 @@ in {
     systemd.services = {
       mailman = {
         description = "GNU Mailman Master Process";
+        before = lib.optional cfg.enablePostfix "postfix.service";
         after = [ "network.target" ]
           ++ lib.optional cfg.enablePostfix "postfix-setup.service";
         restartTriggers = [ config.environment.etc."mailman.cfg".source ];