Drop linux capabilities and rework users/groups

* Drop linux capabilities for unprivileged containerized
  worlkoads Kargo configures for deployments.
* Configure required securityContext/user/group/groups for kube
  components' static manifests, etcd, calico-rr and k8s apps,
  like dnsmasq daemonset.
* Rework cloud-init (etcd) users creation for CoreOS.
* Fix nologin paths, adjust defaults for addusers role and ensure
  supplementary groups membership added for users.
* Add netplug user for network plugins (yet unused by privileged
  networking containers though).
* Grant the kube and netplug users read access for etcd certs via
  the etcd certs group.
* Grant group read access to kube certs via the kube cert group.
* Remove priveleged mode for calico-rr and run it under its uid/gid
  and supplementary etcd_cert group.
* Adjust docs.
* Align cpu/memory limits and dropped caps with added rkt support
  for control plane.

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>

roles/kubernetes/preinstall/meta/main.yml

@@ -2,4 +2,7 @@
 dependencies:
   - role: adduser
     user: "{{ addusers.kube }}"
-    tags: kubelet
+    tags: [bootstrap-os, kubelet]
+  - role: adduser
+    user: "{{ addusers.netplug }}"
+    tags: [bootstrap-os, network]

roles/kubernetes/preinstall/tasks/main.yml

@@ -23,6 +23,12 @@
 - include: set_facts.yml
   tags: facts
 
+- include: set_resolv_facts.yml
+  tags: [bootstrap-os, resolvconf, facts]
+
+- include: set_uid_facts.yml
+  tags: [bootstrap-os, facts]
+
 - name: gather os specific variables
   include_vars: "{{ item }}"
   with_first_found:
@@ -42,7 +48,7 @@
   file:
     path: "{{ kube_config_dir }}"
     state: directory
-    owner: kube
+    owner: "{{ kubelet_user }}"
   when: "{{ inventory_hostname in groups['k8s-cluster'] }}"
   tags: [kubelet, k8s-secrets, kube-controller-manager, kube-apiserver, bootstrap-os, apps, network, master, node]
 
@@ -50,7 +56,7 @@
   file:
     path: "{{ kube_script_dir }}"
     state: directory
-    owner: kube
+    owner: "{{ kubelet_user }}"
   when: "{{ inventory_hostname in groups['k8s-cluster'] }}"
   tags: [k8s-secrets, bootstrap-os]
 
@@ -58,7 +64,7 @@
   file:
     path: "{{ kube_manifest_dir }}"
     state: directory
-    owner: kube
+    owner: "{{ kubelet_user }}"
   when: "{{ inventory_hostname in groups['k8s-cluster'] }}"
   tags: [kubelet, bootstrap-os, master, node]
 
@@ -80,7 +86,7 @@
   file:
     path: "{{ item }}"
     state: directory
-    owner: kube
+    owner: "{{ kubelet_user }}"
   with_items:
     - "/etc/cni/net.d"
     - "/opt/cni/bin"

roles/kubernetes/preinstall/tasks/set_facts.yml

@@ -51,6 +51,3 @@
     etcd_container_bin_dir: "{% if etcd_after_v3 %}/usr/local/bin/{% else %}/{% endif %}"
 - set_fact:
     peer_with_calico_rr: "{{ 'calico-rr' in groups and groups['calico-rr']|length > 0 }}"
-
-- include: set_resolv_facts.yml
-  tags: [bootstrap-os, resolvconf, facts]

roles/kubernetes/preinstall/tasks/set_uid_facts.yml

@@ -0,0 +1,32 @@
+---
+- name: Preinstall | get kube user ID
+  shell: /usr/bin/id -u {{ kubelet_user }} || echo 0
+  register: kube_uid
+
+- name: Preinstall | get kube group ID
+  shell: /usr/bin/id -g {{ kubelet_group }} || echo 0
+  register: kube_gid
+
+- name: Preinstall | get kube cert group ID
+  shell: /usr/bin/id -g {{ kube_cert_group }} || echo 0
+  register: kube_cert_gid
+
+- name: Preinstall | get etcd cert group ID
+  shell: /usr/bin/id -g {{ etcd_cert_group }} || echo 0
+  register: etcd_cert_gid
+
+- name: Preinstall | get netplug user ID
+  shell: /usr/bin/id -u {{ netplug_user }} || echo 0
+  register: netplug_uid
+
+- name: Preinstall | get netplug group ID
+  shell: /usr/bin/getent group {{ netplug_group }} | cut -d':' -f3 || echo 0
+  register: netplug_gid
+
+- set_fact:
+    kubelet_user_id: "{{ kube_uid.stdout }}"
+    kubelet_group_id: "{{ kube_gid.stdout }}"
+    kube_cert_group_id: "{{ kube_cert_gid.stdout }}"
+    etcd_cert_group_id: "{{ etcd_cert_gid.stdout }}"
+    netplug_user_id: "{{ netplug_uid.stdout }}"
+    netplug_group_id: "{{ netplug_gid.stdout }}"