Keep compute nodes off when power comes back

When the power comes back, we don't know if the AC unit will be
operating properly or if the room will be at a safe temperature. So,
instead of powering all the machines back, only configure the login to
power on, so we can check the state of the room and power the rest of
the machines.

m/apex/configuration.nix

@@ -5,9 +5,12 @@
     ../common/xeon.nix
     ../common/ssf/hosts.nix
     ../module/ceph.nix
+    ../module/power-policy.nix
     ./nfs.nix
   ];
 
+  power.policy = "always-on";
+
   # Don't install grub MBR for now
   boot.loader.grub.device = "nodev";
 

m/common/base/always-power-on.nix

@@ -1,8 +0,0 @@
-{
-  imports = [
-    ../../module/power-policy.nix
-  ];
-
-  # Turn on as soon as we have power
-  power.policy = "always-on";
-}

m/common/base/power-policy.nix

@@ -0,0 +1,9 @@
+{
+  imports = [
+    ../../module/power-policy.nix
+  ];
+
+  # By default, keep the machines off as we don't know if the AC will be working
+  # once the electricity comes back.
+  power.policy = "always-off";
+}

m/fox/configuration.nix

@@ -6,8 +6,11 @@
     ../common/xeon/console.nix
     ../module/emulation.nix
     ../module/nvidia.nix
+    ../module/power-policy.nix
   ];
 
+  power.policy = "always-on";
+
   # Don't turn off on August as UPC has different dates.
   # Fox works fine on power cuts.
   systemd.timers.august-shutdown.enable = false;

m/raccoon/configuration.nix

@@ -7,9 +7,12 @@
     ../module/debuginfod.nix
     ../module/ssh-hut-extern.nix
     ../module/nvidia.nix
+    ../module/power-policy.nix
     ../eudy/kernel/perf.nix
   ];
 
+  power.policy = "always-on";
+
   # Don't install Grub on the disk yet
   boot.loader.grub.device = "nodev";