lxc-containers.nix: refactor with imperative build-container script

nix/nixos-module/server/lxc-containers.nix

@@ -2,14 +2,11 @@
 
 let
   containers =
-    # TODO: remove 1 line
-    lib.filterAttrs (ctName: _: ctName == "upstream1") (
     lib.filterAttrs (_: { role, model, location, ... }:
       role == "container" &&
       model == "lxc" &&
       location == hostName
-    ) config.site.hosts
-    );
+    ) config.site.hosts;
 
   enabled = containers != {};
 
@@ -58,6 +55,44 @@ let
         else throw "Invalid data in lxc net config: ${lib.generators.toPretty {} x}";
     in
       serialize "lxc.net" config;
+
+  build-script = pkgs.writeScriptBin "build-container" ''
+    #! ${pkgs.runtimeShell} -e
+
+    if [ -z "$1" ]; then
+      echo "Usage: $0 [containers ...]"
+      exit 1
+    fi
+
+    mkdir -p /nix/var/nix/gcroots/lxc
+
+    for c in $@; do
+      echo Building $c
+      nix build -o /nix/var/nix/gcroots/lxc/$c zentralwerk-network#$c-rootfs
+      SYSTEM=$(readlink /nix/var/nix/gcroots/lxc/$c)
+
+      echo Installing $c
+      for d in \
+        bin dev etc home mnt \
+        nix/store nix/var \
+        proc root run sys tmp var usr ; \
+      do
+        mkdir -p /var/lib/lxc/$c/rootfs/$d
+      done
+      ln -fs $SYSTEM/init /var/lib/lxc/$c/rootfs/init
+
+      set +e
+      active=$(systemctl is-active lxc@$c)
+      if [[ "$active" = active ]] ; then
+        echo Activating $c
+        systemctl reload lxc@$c
+      else
+        echo Starting $c
+        systemctl start lxc@$c
+      fi
+      set -e
+    done
+  '';
 in
 {
   virtualisation.lxc = lib.mkIf enabled {
@@ -70,7 +105,7 @@ in
     '';
   };
 
-  environment.systemPackages = [ pkgs.lxc ];
+  environment.systemPackages = [ pkgs.lxc build-script ];
 
   environment.etc =
     builtins.foldl' (etc: ctName: etc // {
@@ -113,30 +148,8 @@ in
       "lxc/common.conf".source = "${pkgs.lxc}/share/lxc/config/common.conf";
     } (builtins.attrNames containers);
 
-  systemd.services."lxc-rootfs@" = {
-    description = "rootfs for '%i'";
-    requires = [ "nix-daemon.service" ];
-    after = [ "network.target" ];
-    path = [ config.nix.package pkgs.util-linux pkgs.git ];
-    scriptArgs = "%i";
-    script = ''
-      mkdir -p /nix/var/nix/gcroots/lxc
-
-      [ ! -e /nix/var/nix/gcroots/lxc/$1 ] &&
-        flock /tmp/lxc-rootfs-build.lock -c \
-        "nix build -o /nix/var/nix/gcroots/lxc/$1 zentralwerk-network#$1-rootfs"
-
-      SYSTEM=$(readlink /nix/var/nix/gcroots/lxc/$1)
-      mkdir -p /var/lib/lxc/$1/rootfs/{bin,dev,etc,home,mnt,nix/store,nix/var,proc,root,run,sys,tmp,var,usr}
-      ln -fs $SYSTEM/init /var/lib/lxc/$1/rootfs/init
-      exit 0
-    '';
-    serviceConfig.Type = "oneshot";
-  };
-
   systemd.services."lxc@" = {
     description = "LXC container '%i'";
-    requires = [ "lxc-rootfs@%i.service" ];
     after = [ "network.target" ];
     serviceConfig = {
       Type = "simple";
@@ -145,7 +158,11 @@ in
           script = pkgs.writeScript "start-lxc-container.sh" ''
             #! ${pkgs.runtimeShell} -e
 
-            [ -e /var/lib/lxc/$1/rootfs ]
+            if [ ! -e /var/lib/lxc/$1/rootfs ]; then
+              echo "Container $1 does not exist. Run: build-container $1"
+              exit 1
+            fi
+
             exec ${pkgs.lxc}/bin/lxc-start -F -C -n $1
           '';
         in
@@ -170,19 +187,7 @@ in
 
   systemd.targets.lxc-containers = {
     wantedBy = [ "multi-user.target" ];
-    wants = builtins.concatMap (ctName: [ "lxc@${ctName}.service" "lxc-reload@${ctName}.path" ])
+    wants = map (ctName: "lxc@${ctName}.service")
       (builtins.attrNames containers);
   };
-
-  systemd.paths."lxc-reload@" = {
-    pathConfig = {
-      PathChanged = "/var/lib/lxc/%i/rootfs/init";
-    };
-  };
-  systemd.services."lxc-reload@" = {
-    requires = [ "lxc@%i.service" ];
-    serviceConfig.Type = "oneshot";
-    scriptArgs = "%i";
-    script = "/run/current-system/systemd/bin/systemctl reload lxc@$1.service || true";
-  };
 }