=======================
Zun - Container service
=======================

"Zun is an OpenStack Container service. It aims to provide an
OpenStack API for provisioning and managing containerized
workload on OpenStack."
For more details about Zun, see `OpenStack Zun Documentation
<https://docs.openstack.org/zun/latest/>`__.

Preparation and Deployment
--------------------------

Zun requires kuryr and etcd services, for more information about how to
configure kuryr refer to :doc:`../containers/kuryr-guide`.

To allow Zun Compute connect to the Docker Daemon, add the following in the
``docker.service`` file on each zun-compute node.

.. code-block:: ini

   ExecStart= -H tcp://<DOCKER_SERVICE_IP>:2375 -H unix:///var/run/docker.sock --cluster-store=etcd://<DOCKER_SERVICE_IP>:2379 --cluster-advertise=<DOCKER_SERVICE_IP>:2375

.. note::

   ``DOCKER_SERVICE_IP`` is zun-compute host IP address. ``2375`` is port that
   allows Docker daemon to be accessed remotely.

By default zun is disabled in the ``group_vars/all.yml``.
In order to enable it, you need to edit the file globals.yml and set the
following variables:

.. code-block:: yaml

   enable_zun: "yes"
   enable_kuryr: "yes"
   enable_etcd: "yes"

Deploy the OpenStack cloud and zun.

.. code-block:: console

   $ kolla-ansible deploy

Verification
------------

#. Generate the credentials file:

   .. code-block:: console

      $ kolla-ansible post-deploy

#. Source credentials file:

   .. code-block:: console

      $ . /etc/kolla/admin-openrc.sh

#. Download and create a glance container image:

   .. code-block:: console

      $ docker pull cirros
      $ docker save cirros | openstack image create cirros --public \
        --container-format docker --disk-format raw

#. Create zun container:

   .. code-block:: console

      $ zun create --name test --net network=demo-net cirros ping -c4 8.8.8.8

   .. note::

      Kuryr does not support networks with DHCP enabled, disable DHCP in the
      subnet used for zun containers.

      .. code-block:: console

         $ openstack subnet set --no-dhcp <subnet>

#. Verify container is created:

   .. code-block:: console

      $ zun list

      +--------------------------------------+------+---------------+---------+------------+------------+-------+
      | uuid                                 | name | image         | status  | task_state | addresses  | ports |
      +--------------------------------------+------+---------------+---------+------------+------------+-------+
      | 3719a73e-5f86-47e1-bc5f-f4074fc749f2 | test | cirros        | Created | None       | 172.17.0.3 | []    |
      +--------------------------------------+------+---------------+---------+------------+------------+-------+

#. Start container:

   .. code-block:: console

      $ zun start test
      Request to start container test has been accepted.

#. Verify container:

   .. code-block:: console

      $ zun logs test
      PING 8.8.8.8 (8.8.8.8): 56 data bytes
      64 bytes from 8.8.8.8: seq=0 ttl=45 time=96.396 ms
      64 bytes from 8.8.8.8: seq=1 ttl=45 time=96.504 ms
      64 bytes from 8.8.8.8: seq=2 ttl=45 time=96.721 ms
      64 bytes from 8.8.8.8: seq=3 ttl=45 time=95.884 ms

      --- 8.8.8.8 ping statistics ---
      4 packets transmitted, 4 packets received, 0% packet loss
      round-trip min/avg/max = 95.884/96.376/96.721 ms

For more information about how zun works, see
`zun, OpenStack Container service <https://docs.openstack.org/zun/latest/>`__.