Ansible variables =============== Inventory ------------- The inventory is composed of 3 groups: * **kube-node** : list of kubernetes nodes where the pods will run. * **kube-master** : list of servers where kubernetes master components (apiserver, scheduler, controller) will run. * **etcd**: list of servers to compose the etcd server. You should have at least 3 servers for failover purpose. Note: do not modify the children of _k8s-cluster_, like putting the _etcd_ group into the _k8s-cluster_, unless you are certain to do that and you have it fully contained in the latter: ``` k8s-cluster ⊂ etcd => kube-node ∩ etcd = etcd ``` When _kube-node_ contains _etcd_, you define your etcd cluster to be as well schedulable for Kubernetes workloads. If you want it a standalone, make sure those groups do not intersect. If you want the server to act both as master and node, the server must be defined on both groups _kube-master_ and _kube-node_. If you want a standalone and unschedulable master, the server must be defined only in the _kube-master_ and not _kube-node_. There are also two special groups: * **calico-rr** : explained for [advanced Calico networking cases](calico.md) * **bastion** : configure a bastion host if your nodes are not directly reachable Below is a complete inventory example: ``` ## Configure 'ip' variable to bind kubernetes services on a ## different ip than the default iface node1 ansible_ssh_host=95.54.0.12 ip=10.3.0.1 node2 ansible_ssh_host=95.54.0.13 ip=10.3.0.2 node3 ansible_ssh_host=95.54.0.14 ip=10.3.0.3 node4 ansible_ssh_host=95.54.0.15 ip=10.3.0.4 node5 ansible_ssh_host=95.54.0.16 ip=10.3.0.5 node6 ansible_ssh_host=95.54.0.17 ip=10.3.0.6 [kube-master] node1 node2 [etcd] node1 node2 node3 [kube-node] node2 node3 node4 node5 node6 [k8s-cluster:children] kube-node kube-master ``` Group vars and overriding variables precedence ---------------------------------------------- The group variables to control main deployment options are located in the directory ``inventory/group_vars``. Optional variables are located in the `inventory/group_vars/all.yml`. Mandatory variables that are common for at least one role (or a node group) can be found in the `inventory/group_vars/k8s-cluster.yml`. There are also role vars for docker, rkt, kubernetes preinstall and master roles. According to the [ansible docs](http://docs.ansible.com/ansible/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable), those cannot be overriden from the group vars. In order to override, one should use the `-e ` runtime flags (most simple way) or other layers described in the docs. Kubespray uses only a few layers to override things (or expect them to be overriden for roles): Layer | Comment ------|-------- **role defaults** | provides best UX to override things for Kubespray deployments inventory vars | Unused **inventory group_vars** | Expects users to use ``all.yml``,``k8s-cluster.yml`` etc. to override things inventory host_vars | Unused playbook group_vars | Unused playbook host_vars | Unused **host facts** | Kubespray overrides for internal roles' logic, like state flags play vars | Unused play vars_prompt | Unused play vars_files | Unused registered vars | Unused set_facts | Kubespray overrides those, for some places **role and include vars** | Provides bad UX to override things! Use extra vars to enforce block vars (only for tasks in block) | Kubespray overrides for internal roles' logic task vars (only for the task) | Unused for roles, but only for helper scripts **extra vars** (always win precedence) | override with ``ansible-playbook -e @foo.yml`` Ansible tags ------------ The following tags are defined in playbooks: | Tag name | Used for |--------------------------|--------- | apps | K8s apps definitions | azure | Cloud-provider Azure | bastion | Setup ssh config for bastion | bootstrap-os | Anything related to host OS configuration | calico | Network plugin Calico | canal | Network plugin Canal | cloud-provider | Cloud-provider related tasks | dnsmasq | Configuring DNS stack for hosts and K8s apps | docker | Configuring docker for hosts | download | Fetching container images to a delegate host | etcd | Configuring etcd cluster | etcd-pre-upgrade | Upgrading etcd cluster | etcd-secrets | Configuring etcd certs/keys | etchosts | Configuring /etc/hosts entries for hosts | facts | Gathering facts and misc check results | flannel | Network plugin flannel | gce | Cloud-provider GCP | hyperkube | Manipulations with K8s hyperkube image | k8s-pre-upgrade | Upgrading K8s cluster | k8s-secrets | Configuring K8s certs/keys | kpm | Installing K8s apps definitions with KPM | kube-apiserver | Configuring self-hosted kube-apiserver | kube-controller-manager | Configuring self-hosted kube-controller-manager | kubectl | Installing kubectl and bash completion | kubelet | Configuring kubelet service | kube-proxy | Configuring self-hosted kube-proxy | kube-scheduler | Configuring self-hosted kube-scheduler | localhost | Special steps for the localhost (ansible runner) | master | Configuring K8s master node role | netchecker | Installing netchecker K8s app | network | Configuring networking plugins for K8s | nginx | Configuring LB for kube-apiserver instances | node | Configuring K8s minion (compute) node role | openstack | Cloud-provider OpenStack | preinstall | Preliminary configuration steps | resolvconf | Configuring /etc/resolv.conf for hosts/apps | upgrade | Upgrading, f.e. container images/binaries | upload | Distributing images/binaries across hosts | weave | Network plugin Weave Note: Use the ``bash scripts/gen_tags.sh`` command to generate a list of all tags found in the codebase. New tags will be listed with the empty "Used for" field. Example commands ---------------- Example command to filter and apply only DNS configuration tasks and skip everything else related to host OS configuration and downloading images of containers: ``` ansible-playbook -i inventory/inventory.ini cluster.yml --tags preinstall,dnsmasq,facts --skip-tags=download,bootstrap-os ``` And this play only removes the K8s cluster DNS resolver IP from hosts' /etc/resolv.conf files: ``` ansible-playbook -i inventory/inventory.ini -e dns_server='' cluster.yml --tags resolvconf ``` And this prepares all container images localy (at the ansible runner node) without installing or upgrading related stuff or trying to upload container to K8s cluster nodes: ``` ansible-playbook -i inventory/inventory.ini cluster.yml \ -e download_run_once=true -e download_localhost=true \ --tags download --skip-tags upload,upgrade ``` Note: use `--tags` and `--skip-tags` wise and only if you're 100% sure what you're doing. Bastion host -------------- If you prefer to not make your nodes publicly accessible (nodes with private IPs only), you can use a so called *bastion* host to connect to your nodes. To specify and use a bastion, simply add a line to your inventory, where you have to replace x.x.x.x with the public IP of the bastion host. ``` bastion ansible_ssh_host=x.x.x.x ``` For more information about Ansible and bastion hosts, read [Running Ansible Through an SSH Bastion Host](http://blog.scottlowe.org/2015/12/24/running-ansible-through-ssh-bastion-host/)