---
title: Requirements for Calico with Mesos
canonical_url: 'https://docs.projectcalico.org/v2.6/getting-started/mesos/installation/dc-os/'
---

#### 1. etcd

Calico uses etcd as its datastore. Ensure you have an instance of etcd running,
and that it is accessible from all Agents in your cluster.

In order to maximize availability, use [etcd's clustering guide](https://coreos.com/os/docs/latest/cluster-architectures.html)
and run etcd across the masters or other dedicated hosts.

For simplicity, you can quickly get started by running a single instance of etcd
using Docker. Run the following command on a Master, ensure you've correctly set
or replaced `$ETCD_IP` and `$ETCD_PORT`:

```shell
docker run --detach \
	--net=host \
	--name etcd quay.io/coreos/etcd:v3.1.10 \
	etcd --advertise-client-urls "http://$ETCD_IP:$ETCD_PORT" \
	--listen-client-urls "http://$ETCD_IP:$ETCD_PORT,http://127.0.0.1:$ETCD_PORT"
```

Check that etcd is up and running:

```shell
$ curl http://$ETCD_IP:$ETCD_PORT/version
{"etcdserver":"2.2.5","etcdcluster":"2.2.0"}
```

#### 2. Docker Configured with Cluster Store

Under the covers, Calico networks Docker tasks for Mesos with its Docker CNM
plugin. Multihost Networking in Docker requires that each Agent's Docker daemon
be configured with a cluster store.

Though Docker's configured cluster-store does not have to be the same as
Calico's, for simplicity, users can configure Docker to use the same datastore
as Calico by setting the following flag when starting the docker daemon:

```shell
--cluster-store=etcd://$ETCD_IP:$ETCD_PORT
```

> **Note**: Set or replace `$ETCD_IP` and `$ETCD_PORT` with the appropriate 
> address of your etcd cluster.
{: .alert .alert-info}


Restart Docker, then ensure it has picked up the changes:

```
$ docker info | grep -i "cluster store"
Cluster Store: etcd://10.0.0.1:2379
```

#### 3. Docker Containerizer Enabled for Mesos Agents

By default, Mesos only enables the "Mesos" Containerizer. Ensure
the Docker Containerizer is also enabled on each Agent.

> **Note**: You may skip this step if you do not plan on using the Docker 
> Containerizer.
{: .alert .alert-info}


If you are using the default `mesos-init-wrapper` from the official Mesos package,
you can enable the Docker Containerizer with the following command:

```shell
$ sh -c 'echo docker > /etc/mesos-slave/containerizers'
$ systemctl restart mesos-slave.service
```

#### 4. CNI Isolator Enabled for Mesos Agents

If you are planning to use Calico with the Unified containerizer,
[enable the CNI Isolator on each agent](http://mesos.apache.org/documentation/latest/cni/#usage)

> **Note**: You may skip this step if you do not plan on using the 
> Unified Containerizer.
{: .alert .alert-info}

When enabling CNI, you will have specified a `network_cni_config_dir`
and `network_cni_plugins_dir`. We'll refer to these going forward as
`$NETWORK_CNI_CONFIG_DIR` and `$NETWORK_CNI_PLUGINS_DIR`, respectively.

## Next Steps

Once you have met the prerequisites, view the [Integration Guide](integration)

[slack]: https://slack.projectcalico.org
