title: Docker Swarm managers acting nodes?
body: <p>I've created setup with 3 swarm managers and 3 nodes.</p>
  
  <p>You e can see below that in the case with 3 masters and 3 workers actually I have <strong>3 managers and 6 nodes</strong>. Is it idea that managers are also capable to run containers, not just workers? Am I missing something in the setup or this is intended to work  as it is now?</p>
  
  <p>when I execute docker info command, I am getting this output:</p>
  
  <pre><code>ubuntu@manager3:~$ docker info
  Containers: 4
   Running: 3
   Paused: 0
   Stopped: 1
  Images: 3
  Server Version: 1.12.0
  Storage Driver: aufs
   Root Dir: /var/lib/docker/aufs
   Backing Filesystem: extfs
   Dirs: 23
   Dirperm1 Supported: false
  Logging Driver: json-file
  Cgroup Driver: cgroupfs
  Plugins:
   Volume: local
   Network: overlay bridge host null
  Swarm: active
   NodeID: 9uv3xhwzibx52xghpsa0sp3f7
   Is Manager: true
   ClusterID: 04r095rvj6b4i7ygbnr2quo9e
   **Managers: 3
   Nodes: 6**
   Orchestration:
    Task History Retention Limit: 5
   Raft:
    Snapshot interval: 10000
    Heartbeat tick: 1
    Election tick: 3
   Dispatcher:
    Heartbeat period: 5 seconds
   CA configuration:
    Expiry duration: 3 months
   Node Address: 172.100.0.23
  Runtimes: runc
  Default Runtime: runc
  Security Options: apparmor
  Kernel Version: 3.13.0-92-generic
  Operating System: Ubuntu 14.04.4 LTS
  OSType: linux
  Architecture: x86_64
  CPUs: 1
  Total Memory: 992.5 MiB
  Name: manager3
  ID: MUXB:GUNV:HIDO:APRJ:S2JU:763E:QSOL:2554:EZJL:L4OI:6TS5:RD7O
  Docker Root Dir: /var/lib/docker
  Debug Mode (client): false
  Debug Mode (server): false
  Registry: https://index.docker.io/v1/
  WARNING: No swap limit support
  Insecure Registries:
   127.0.0.0/8
  </code></pre>
  
  <p>when I create some services to run on swarm cluster:</p>
  
  <p><code>docker service create --replicas=3 --name redis redis:latest</code></p>
  
  <p>Some of them will run on managers, some on workers. That's confusing me.</p>
  
  <p>if I create more services</p>
  
  <p><code>docker service create --replicas=6 --name redis redis:latest</code></p>
  
  <p>they will run on all machines in cluster. increasing even more will start failing due to port collision. </p>