.. _restarting-a-machine-in-a-kubernetes-cluster:

Restarting a machine in a Kubernetes cluster
============================================

.. note::

    1. Know which kind of machine is going to be restarted

        a) control plane (api-server, controllers, etc.)
        b) node (runs actual workload, e.g. *Brig* or *Webapp*)
        c) *a* and *b* combined

    2. The kind of machine in question must be deployed redundantly
    3. Take out machines in a rolling fashion (sequentially, one at a time)


Control plane
~~~~~~~~~~~~~

Depending on whether *etcd* is hosted on the same machine alongside the control plane (common practise), you need
to take its implications into account (see :ref:`How to rolling-restart an etcd cluster <how-to-rolling-restart-an-etcd-cluster>`)
when restarting a machine.

Regardless of where *etcd* is located, before turning off any machine that is part of the control plane, one should
:ref:`back up the cluster state <etcd_backup-and-restore>`.

If a part of the control plane does not run sufficiently redundant, it is advised to prevent any mutating interaction
during the procedure, until the cluster is healthy again.

.. code:: bash

    kubectl get nodes


Node
~~~~

.. rubric:: High-level steps:

1. Drain the node so that all workload is rescheduled on other nodes
2. Restart / Update / Decommission
3. Mark the node as being schedulable again (if not decommissioned)

*For more details please refer to the official documentation:* `Safely Drain a Node <https://kubernetes.io/docs/tasks/administer-cluster/safely-drain-node/>`__