diff --git a/juju/home-maas/00-variables.tf b/juju/home-maas/00-variables.tf
index dd31ceb..455903a 100644
--- a/juju/home-maas/00-variables.tf
+++ b/juju/home-maas/00-variables.tf
@@ -1,3 +1,32 @@
+######## vars to change as per env
+variable "cloud" {
+    type = string
+    default = "home-maas"
+}
+
+variable "num_units" {
+    type = number
+    default = 3
+}
+
+variable "controller_ids" {
+  type    = list(string)
+  default = ["100", "101", "102", 
+             "103", "104", "105"]
+}
+
+variable "compute_ids" {
+  type    = list(string)
+  default = ["1000", "1001", "1002", "1003", 
+             "1004", "1005", "1006", "1007"]
+}
+
+variable "apt_mirror" {
+    type = string
+    default = "192.168.1.12"
+}
+
+######## vars unlikely to be changed
 variable "machines" {
   type = list(object({
     machine_id = number
@@ -35,6 +64,71 @@ variable mysql-channel {
     default = "8.0/stable"
 }
 
+variable mysql-router-channel {
+    type = string
+    default = "8.0/stable"
+}
+
+variable "hacluster-channel" {
+    type = string
+    default = "2.0.3/stable"
+}
+
+variable "rabbitmq-server-channel" {
+    type = string
+    default = "3.8/stable"
+}
+
+variable "ceph-channel" {
+    type = string
+    default = "octopus/stable"
+}
+
+variable "lxd_snap_channel" {
+    type = string
+    default = "5.0/stable"
+}
+
+variable "sysconfig_compute_channel" {
+    type = string
+    default = "latest/stable"
+}
+
+variable "sysconfig_compute_revision" {
+    type = string
+    default = "19"
+}
+
+variable "ubuntu_channel" {
+    type = string
+    default = "latest/stable"
+}
+
+variable "ubuntu_revision" {
+    type = string
+    default = "24"
+}
+
+variable "vault_channel" {
+    type = string
+    default = "1.7/stable"
+}
+
+variable "etcd_channel" {
+    type = string
+    default = "latest/stable"
+}
+
+variable "etcd_revision" {
+    type = string
+    default = "583"
+}
+
+variable "easyrsa_channel" {
+    type = string
+    default = "latest/stable"
+}
+
 variable osd-devices {
     type = string
     default = ""
diff --git a/juju/home-maas/01-cloud.tf b/juju/home-maas/01-cloud.tf
index 4c393e7..01e057e 100644
--- a/juju/home-maas/01-cloud.tf
+++ b/juju/home-maas/01-cloud.tf
@@ -2,19 +2,19 @@ resource "juju_model" "openstack" {
   name = var.model-name
 
   cloud {
-    name = "home-maas"
+    name = var.cloud
   }
 
   config = {
     cloudinit-userdata = file("user-data.yaml")
 
-    apt-mirror = "http://192.168.1.12/archive.ubuntu.com/ubuntu"
-    lxd-snap-channel = "5.0/stable"
+    apt-mirror = "http://${var.apt_mirror}/archive.ubuntu.com/ubuntu"
+    lxd-snap-channel = var.lxd_snap_channel
 
-    container-image-metadata-url = "http://192.168.1.12/lxd/"
+    container-image-metadata-url = "http://${var.apt_mirror}/lxd/"
     container-image-stream = "released"
 
-    agent-metadata-url = "http://192.168.1.12/juju/tools/"
+    agent-metadata-url = "http://${var.apt_mirror}/juju/tools/"
     agent-stream = "released"
   }
 }
diff --git a/juju/home-maas/04-keystone.tf b/juju/home-maas/04-keystone.tf
index 42a0321..449586b 100644
--- a/juju/home-maas/04-keystone.tf
+++ b/juju/home-maas/04-keystone.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "keystone-1" {
+resource "juju_machine" "keystone" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["103"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "keystone-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["104"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "keystone-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["105"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index+var.num_units]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -24,12 +15,11 @@ resource "juju_application" "keystone" {
     channel  = var.openstack-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.keystone-1.machine_id,
-    juju_machine.keystone-2.machine_id,
-    juju_machine.keystone-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, var.num_units, length(var.controller_ids)) : 
+        juju_machine.keystone[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -66,7 +56,7 @@ resource "juju_application" "keystone-mysql-router" {
 
   charm {
     name = "mysql-router"
-    channel = "8.0/stable"
+    channel = var.mysql-router-channel
   }
 
   units = 0
@@ -93,7 +83,7 @@ resource "juju_application" "hacluster-keystone" {
 
   charm {
     name    = "hacluster"
-    channel = "2.0.3/stable"
+    channel = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/04-mysql.tf b/juju/home-maas/04-mysql.tf
index 2e0f3e1..0b41852 100644
--- a/juju/home-maas/04-mysql.tf
+++ b/juju/home-maas/04-mysql.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "mysql-1" {
+resource "juju_machine" "mysql" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["100"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "mysql-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["101"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "mysql-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["102"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -25,12 +16,11 @@ resource "juju_application" "mysql-innodb-cluster" {
     base     = var.default-base
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.mysql-1.machine_id,
-    juju_machine.mysql-2.machine_id,
-    juju_machine.mysql-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.mysql[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
diff --git a/juju/home-maas/04-rmq.tf b/juju/home-maas/04-rmq.tf
index 3b485b2..a577516 100644
--- a/juju/home-maas/04-rmq.tf
+++ b/juju/home-maas/04-rmq.tf
@@ -1,19 +1,9 @@
-resource "juju_machine" "rmq-1" {
+resource "juju_machine" "rmq" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["103"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids_high[count.index+var.num_units]].machine_id])
   constraints = "spaces=oam"
 }
-resource "juju_machine" "rmq-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["104"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "rmq-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["105"].machine_id])
-  constraints = "spaces=oam"
-}
-
 
 resource "juju_application" "rabbitmq-server" {
   name = "rabbitmq-server"
@@ -22,15 +12,14 @@ resource "juju_application" "rabbitmq-server" {
 
   charm {
     name     = "rabbitmq-server"
-    channel  = "3.8/stable"
+    channel  = var.rabbitmq-server-channel
   }
 
   units = 3
 
-  placement = "${join(",",sort([
-    juju_machine.rmq-1.machine_id,
-    juju_machine.rmq-2.machine_id,
-    juju_machine.rmq-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, var.num_units, length(var.controller_ids)) : 
+        juju_machine.rmq[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
diff --git a/juju/home-maas/05-ceilometer.tf b/juju/home-maas/05-ceilometer.tf
index 15f0cf6..18d0751 100644
--- a/juju/home-maas/05-ceilometer.tf
+++ b/juju/home-maas/05-ceilometer.tf
@@ -1,19 +1,9 @@
-resource "juju_machine" "ceilometer-1" {
+resource "juju_machine" "ceilometer" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["103"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids_high[count.index+var.num_units]].machine_id])
   constraints = "spaces=oam"
 }
-resource "juju_machine" "ceilometer-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["104"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "ceilometer-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["105"].machine_id])
-  constraints = "spaces=oam"
-}
-
 
 resource "juju_application" "ceilometer" {
   name = "ceilometer"
@@ -27,10 +17,9 @@ resource "juju_application" "ceilometer" {
 
   units = 3
 
-  placement = "${join(",",sort([
-    juju_machine.ceilometer-1.machine_id,
-    juju_machine.ceilometer-2.machine_id,
-    juju_machine.ceilometer-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, var.num_units, length(var.controller_ids)) : 
+        juju_machine.ceilometer[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
diff --git a/juju/home-maas/05-ceph.tf b/juju/home-maas/05-ceph.tf
index 45cf302..3451a42 100644
--- a/juju/home-maas/05-ceph.tf
+++ b/juju/home-maas/05-ceph.tf
@@ -5,20 +5,15 @@ resource "juju_application" "ceph-osd" {
 
   charm {
     name    = "ceph-osd"
-    channel = "octopus/stable"
+    channel = var.ceph-osd-channel
   }
 
-  units = 8
-  placement = "${join(",",sort([
-    juju_machine.all_machines["1000"].machine_id,
-    juju_machine.all_machines["1001"].machine_id,
-    juju_machine.all_machines["1002"].machine_id,
-    juju_machine.all_machines["1003"].machine_id,
-    juju_machine.all_machines["1004"].machine_id,
-    juju_machine.all_machines["1005"].machine_id,
-    juju_machine.all_machines["1006"].machine_id,
-    juju_machine.all_machines["1007"].machine_id,
-   ]))}"
+  units = length(var.compute_ids)
+
+  placement = "${join(",", sort([
+    for index, _ in var.compute_ids : 
+      juju_machine.all_machines[index].machine_id
+  ]))}"
 
   config = {
     osd-devices     = var.osd-devices
@@ -32,19 +27,10 @@ resource "juju_application" "ceph-osd" {
   }
 }
 
-resource "juju_machine" "ceph-mon-1" {
+resource "juju_machine" "ceph-mon" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["100"].machine_id])
-  constraints = "spaces=oam,ceph-access,ceph-replica"
-}
-resource "juju_machine" "ceph-mon-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["101"].machine_id])
-  constraints = "spaces=oam,ceph-access,ceph-replica"
-}
-resource "juju_machine" "ceph-mon-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["102"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index]].machine_id])
   constraints = "spaces=oam,ceph-access,ceph-replica"
 }
 
@@ -55,15 +41,14 @@ resource "juju_application" "ceph-mon" {
 
   charm {
     name     = "ceph-mon"
-    channel  = "octopus/stable"
+    channel  = var.ceph-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.ceph-mon-1.machine_id,
-    juju_machine.ceph-mon-2.machine_id,
-    juju_machine.ceph-mon-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.ceph-mon[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -93,19 +78,10 @@ resource "juju_application" "ceph-mon" {
   }
 }
 
-resource "juju_machine" "ceph-rgw-1" {
+resource "juju_machine" "ceph-rgw" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["100"].machine_id])
-  constraints = "spaces=oam,ceph-access"
-}
-resource "juju_machine" "ceph-rgw-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["101"].machine_id])
-  constraints = "spaces=oam,ceph-access"
-}
-resource "juju_machine" "ceph-rgw-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["102"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index]].machine_id])
   constraints = "spaces=oam,ceph-access"
 }
 
@@ -116,15 +92,14 @@ resource "juju_application" "ceph-radosgw" {
 
   charm {
     name     = "ceph-radosgw"
-    channel  = "octopus/stable"
+    channel  = var.ceph-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.ceph-rgw-1.machine_id,
-    juju_machine.ceph-rgw-2.machine_id,
-    juju_machine.ceph-rgw-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.ceph-rgw[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -161,7 +136,7 @@ resource "juju_application" "hacluster-radosgw" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/05-cinder.tf b/juju/home-maas/05-cinder.tf
index 8848173..bc0fd3e 100644
--- a/juju/home-maas/05-cinder.tf
+++ b/juju/home-maas/05-cinder.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "cinder-1" {
+resource "juju_machine" "cinder" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["100"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "cinder-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["101"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "cinder-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["102"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -24,12 +15,11 @@ resource "juju_application" "cinder" {
     channel  = var.openstack-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.cinder-1.machine_id,
-    juju_machine.cinder-2.machine_id,
-    juju_machine.cinder-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.cinder[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -85,7 +75,7 @@ resource "juju_application" "cinder-mysql-router" {
 
   charm {
     name    = "mysql-router"
-    channel = "8.0/stable"
+    channel = var.mysql-router-channel
   }
 
   units = 0
@@ -112,7 +102,7 @@ resource "juju_application" "hacluster-cinder" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/05-glance.tf b/juju/home-maas/05-glance.tf
index 9dd8396..9b382ec 100644
--- a/juju/home-maas/05-glance.tf
+++ b/juju/home-maas/05-glance.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "glance-1" {
+resource "juju_machine" "glance" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["100"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "glance-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["101"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "glance-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["102"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -24,12 +15,11 @@ resource "juju_application" "glance" {
     channel  = var.openstack-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.glance-1.machine_id,
-    juju_machine.glance-2.machine_id,
-    juju_machine.glance-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.glance[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -65,7 +55,7 @@ resource "juju_application" "glance-mysql-router" {
 
   charm {
     name    = "mysql-router"
-    channel = "8.0/stable"
+    channel = var.mysql-router-channel
   }
 
   units = 0
@@ -92,7 +82,7 @@ resource "juju_application" "hacluster-glance" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/05-gnocchi.tf b/juju/home-maas/05-gnocchi.tf
index 412d36a..bba71cd 100644
--- a/juju/home-maas/05-gnocchi.tf
+++ b/juju/home-maas/05-gnocchi.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "gnocchi-1" {
+resource "juju_machine" "gnocchi" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["103"].machine_id])
-  constraints = "spaces=oam,ceph-access"
-}
-resource "juju_machine" "gnocchi-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["104"].machine_id])
-  constraints = "spaces=oam,ceph-access"
-}
-resource "juju_machine" "gnocchi-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["105"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index+var.num_units]].machine_id])
   constraints = "spaces=oam,ceph-access"
 }
 
@@ -24,12 +15,11 @@ resource "juju_application" "gnocchi" {
     channel  = var.openstack-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.gnocchi-1.machine_id,
-    juju_machine.gnocchi-2.machine_id,
-    juju_machine.gnocchi-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, var.num_units, length(var.controller_ids)) : 
+        juju_machine.gnocchi[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -70,7 +60,7 @@ resource "juju_application" "gnocchi-mysql-router" {
 
   charm {
     name    = "mysql-router"
-    channel = "8.0/stable"
+    channel = var.mysql-router-channel
   }
 
   units = 0
@@ -97,7 +87,7 @@ resource "juju_application" "hacluster-gnocchi" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/05-heat.tf b/juju/home-maas/05-heat.tf
index 7e08620..95b7464 100644
--- a/juju/home-maas/05-heat.tf
+++ b/juju/home-maas/05-heat.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "heat-1" {
+resource "juju_machine" "heat" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["100"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "heat-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["101"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "heat-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["102"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -24,12 +15,11 @@ resource "juju_application" "heat" {
     channel  = var.openstack-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.heat-1.machine_id,
-    juju_machine.heat-2.machine_id,
-    juju_machine.heat-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.heat[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -65,7 +55,7 @@ resource "juju_application" "heat-mysql-router" {
 
   charm {
     name    = "mysql-router"
-    channel = "8.0/stable"
+    channel = var.mysql-router-channel
   }
 
   units = 0
@@ -92,7 +82,7 @@ resource "juju_application" "hacluster-heat" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/05-memcache.tf b/juju/home-maas/05-memcache.tf
index 3a70f88..b6f82de 100644
--- a/juju/home-maas/05-memcache.tf
+++ b/juju/home-maas/05-memcache.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "memcache-1" {
+resource "juju_machine" "memcache" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["100"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "memcache-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["101"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "memcache-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["102"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -25,14 +16,14 @@ resource "juju_application" "memcached" {
     base    = var.default-base
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.memcache-1.machine_id,
-    juju_machine.memcache-2.machine_id,
-    juju_machine.memcache-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.memcached[index].machine_id
   ]))}"
 
+
   endpoint_bindings = [{
     space    = var.internal-space
   },{
diff --git a/juju/home-maas/05-nova.tf b/juju/home-maas/05-nova.tf
index 5ea3c57..0e99924 100644
--- a/juju/home-maas/05-nova.tf
+++ b/juju/home-maas/05-nova.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "ncc-1" {
+resource "juju_machine" "ncc" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["103"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "ncc-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["104"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "ncc-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["105"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index+var.num_units]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -24,12 +15,11 @@ resource "juju_application" "nova-cloud-controller" {
     channel  = var.openstack-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.ncc-1.machine_id,
-    juju_machine.ncc-2.machine_id,
-    juju_machine.ncc-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, var.num_units, length(var.controller_ids)) : 
+        juju_machine.ncc[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -73,7 +63,7 @@ resource "juju_application" "nova-cloud-controller-mysql-router" {
 
   charm {
     name    = "mysql-router"
-    channel = "8.0/stable"
+    channel = var.mysql-router-channel
   }
 
   units = 0
@@ -100,7 +90,7 @@ resource "juju_application" "hacluster-nova" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/05-placement.tf b/juju/home-maas/05-placement.tf
index e6a0de8..d15278c 100644
--- a/juju/home-maas/05-placement.tf
+++ b/juju/home-maas/05-placement.tf
@@ -1,16 +1,7 @@
-resource "juju_machine" "placement-1" {
+resource "juju_machine" "placement" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["103"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "placement-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["104"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "placement-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["105"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index+var.num_units]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -24,12 +15,11 @@ resource "juju_application" "placement" {
     channel  = var.openstack-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.placement-1.machine_id,
-    juju_machine.placement-2.machine_id,
-    juju_machine.placement-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, var.num_units, length(var.controller_ids)) : 
+        juju_machine.placement[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -62,7 +52,7 @@ resource "juju_application" "placement-mysql-router" {
 
   charm {
     name    = "mysql-router"
-    channel = "8.0/stable"
+    channel = var.mysql-router-channel
   }
 
   units = 0
@@ -89,7 +79,7 @@ resource "juju_application" "hacluster-placement" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/06-nova-compute.tf b/juju/home-maas/06-nova-compute.tf
index 4a48a28..6b2c383 100644
--- a/juju/home-maas/06-nova-compute.tf
+++ b/juju/home-maas/06-nova-compute.tf
@@ -8,17 +8,12 @@ resource "juju_application" "nova-compute-kvm" {
     channel  = var.openstack-channel
   }
 
-  units = 8
-  placement = "${join(",",sort([
-    juju_machine.all_machines["1000"].machine_id,
-    juju_machine.all_machines["1001"].machine_id,
-    juju_machine.all_machines["1002"].machine_id,
-    juju_machine.all_machines["1003"].machine_id,
-    juju_machine.all_machines["1004"].machine_id,
-    juju_machine.all_machines["1005"].machine_id,
-    juju_machine.all_machines["1006"].machine_id,
-    juju_machine.all_machines["1007"].machine_id,
-   ]))}"
+  units = length(var.compute_ids)
+
+  placement = "${join(",", sort([
+    for index, _ in var.compute_ids : 
+      juju_machine.all_machines[index].machine_id
+  ]))}"
 
    endpoint_bindings = [{
      space    = var.oam-space
@@ -109,8 +104,8 @@ resource "juju_application" "sysconfig-compute" {
 
   charm {
     name     = "sysconfig"
-    channel  = "latest/stable"
-    revision = "19"
+    channel  = var.sysconfig_compute_channel
+    revision = var.sysconfig_compute_revision
   }
 
   units = 0
diff --git a/juju/home-maas/07-controllers.tf b/juju/home-maas/07-controllers.tf
index 9ce1cfc..b4ae5d1 100644
--- a/juju/home-maas/07-controllers.tf
+++ b/juju/home-maas/07-controllers.tf
@@ -5,20 +5,17 @@ resource "juju_application" "controller-server" {
 
   charm {
     name     = "ubuntu"
-    channel  = "latest/stable"
-    revision = "24"
+    channel  = var.ubuntu_channel
+    revision = var.ubuntu_revision
     base     = var.default-base
   }
 
-  units = 6
-  placement = "${join(",",sort([
-    juju_machine.all_machines["100"].machine_id,
-    juju_machine.all_machines["101"].machine_id,
-    juju_machine.all_machines["102"].machine_id,
-    juju_machine.all_machines["103"].machine_id,
-    juju_machine.all_machines["104"].machine_id,
-    juju_machine.all_machines["105"].machine_id,
-   ]))}"
+  units = length(var.controller_ids)
+
+  placement = "${join(",", sort([
+    for index, _ in var.controller_ids : 
+      juju_machine.all_machines[index].machine_id
+  ]))}"
 }
 
 resource "juju_application" "sysconfig-control" {
@@ -28,8 +25,8 @@ resource "juju_application" "sysconfig-control" {
 
   charm {
     name     = "sysconfig"
-    channel  = "latest/stable"
-    revision = "22"
+    channel  = var.sysconfig_compute_channel
+    revision = var.sysconfig_compute_revision
   }
 
   units = 0
diff --git a/juju/home-maas/08-neutron.tf b/juju/home-maas/08-neutron.tf
index 6e1df0e..c5b9b3f 100644
--- a/juju/home-maas/08-neutron.tf
+++ b/juju/home-maas/08-neutron.tf
@@ -8,12 +8,12 @@ resource "juju_application" "neutron-gateway" {
     channel  = var.openstack-channel
   }
 
-  units = 3
-  placement = "${join(",",sort([
-    juju_machine.all_machines["100"].machine_id,
-    juju_machine.all_machines["101"].machine_id,
-    juju_machine.all_machines["102"].machine_id,
-   ]))}"
+  units = var.num_units
+
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.neutron-api[index].machine_id
+  ]))}"
 
 
   config = {
@@ -27,19 +27,10 @@ resource "juju_application" "neutron-gateway" {
   }
 }
 
-resource "juju_machine" "neutron-api-1" {
+resource "juju_machine" "neutron-api" {
+  count       = var.num_units
   model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["100"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "neutron-api-2" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["101"].machine_id])
-  constraints = "spaces=oam"
-}
-resource "juju_machine" "neutron-api-3" {
-  model       = var.model-name
-  placement   = join(":",["lxd",juju_machine.all_machines["102"].machine_id])
+  placement   = join(":", ["lxd", juju_machine.all_machines[var.controller_ids[count.index]].machine_id])
   constraints = "spaces=oam"
 }
 
@@ -53,12 +44,11 @@ resource "juju_application" "neutron-api" {
     channel  = var.openstack-channel
   }
 
-  units = 3
+  units = var.num_units
 
-  placement = "${join(",",sort([
-    juju_machine.neutron-api-1.machine_id,
-    juju_machine.neutron-api-2.machine_id,
-    juju_machine.neutron-api-3.machine_id,
+  placement = "${join(",", sort([
+    for index, _ in slice(var.controller_ids, 0, var.num_units+1) : 
+        juju_machine.neutron-api[index].machine_id
   ]))}"
 
   endpoint_bindings = [{
@@ -106,7 +96,7 @@ resource "juju_application" "neutron-mysql-router" {
 
   charm {
     name     = "mysql-router"
-    channel  = "8.0/stable"
+    channel  = var.mysql-router-channel
   }
 
   units = 0
@@ -133,7 +123,7 @@ resource "juju_application" "hacluster-neutron" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
diff --git a/juju/home-maas/10-vault.tf b/juju/home-maas/10-vault.tf
index f95d9e7..8e245aa 100644
--- a/juju/home-maas/10-vault.tf
+++ b/juju/home-maas/10-vault.tf
@@ -21,7 +21,7 @@ resource "juju_application" "vault" {
 
   charm {
     name    = "vault"
-    channel = "1.7/stable"
+    channel = var.vault_channel
     base    = var.default-base
   }
 
@@ -47,7 +47,7 @@ resource "juju_application" "vault-mysql-router" {
 
   charm {
     name    = "mysql-router"
-    channel = "8.0/stable"
+    channel = var.mysql-router-channel
   }
 
   units = 0
@@ -76,7 +76,7 @@ resource "juju_application" "hacluster-vault" {
 
   charm {
     name     = "hacluster"
-    channel  = "2.0.3/stable"
+    channel  = var.hacluster-channel
   }
 
   units = 0
@@ -106,9 +106,9 @@ resource "juju_application" "etcd" {
 
   charm {
     name     = "etcd"
-    channel  = "latest/stable"
+    channel  = var.etcd_channel
     base     = var.default-base
-    revision = 583
+    revision = var.etcd_revision
   }
 
   placement = "${join(",",sort([
@@ -127,7 +127,7 @@ resource "juju_application" "etcd" {
     endpoint = "db"
   }]
 
-  units = 3
+  units = var.num_units
 
   config = {
     channel = "3.2/stable"
@@ -147,7 +147,7 @@ resource "juju_application" "easyrsa" {
 
   charm {
     name    = "easyrsa"
-    channel = "latest/stable"
+    channel = var.easyrsa_channel
     base    = var.default-base
   }