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