Manage VMs with docker-machine

Introduction

Install software

Create machines

Create the KVM netwrok

Before a new machine can be created with the docker-machine command, the proper KVM virtual network must be created.

See How to create KVM networks for details.

Create machine

Machine can be created with the docker-machine create command. Most simple usage:

docker-machine create -d <hybervisor driver name> --<driver options> <machine name>

-d: hypervisor driver. Default value: "virtalbox". For KVM use: "kvm".
--kvm-network: The name of the kvm virtual (public) network that we would like to use. If this is not set, the new machine will be connected to the "default" KVM virtual network.

Note
Docker will always create a second, isolated virtual network (bridge), called "docker-machines", that all the VMs will be connected to regardless of the value of the --kvm-network paramter that controls only the name of the "public" network. It seems the the name of the isolated virtual network is hardcoded, and can't be changed.

# docker-machine create -d kvm --kvm-network "docker-network" manager

Running pre-create checks...
Creating machine...
(manager) Copying /root/.docker/machine/cache/boot2docker.iso to /root/.docker/machine/machines/manager/boot2docker.iso...
Waiting for machine to be running, this may take a few minutes...
Detecting operating system of created instance...
Waiting for SSH to be available...
Detecting the provisioner...
Provisioning with boot2docker...
Copying certs to the local machine directory...
Copying certs to the remote machine...
Setting Docker configuration on the remote daemon...
Checking connection to Docker...
Docker is up and running!
To see how to connect your Docker Client to the Docker Engine running on this virtual machine, run: docker-machine env manager

Tip
The machine is created under /USER_HOME/.docker/machine/machines/<machine_name> directory

If the new VM was created with virtualbox driver, the VirtualBox graphical interface must be started with the same user, that the VM was created with, and the VirtualBox will discover the new VM automatically

Check what was created

Interfaces on the host

# ifconfig
eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.105  netmask 255.255.255.0  broadcast 192.168.0.255
        ....
virbr1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.42.1  netmask 255.255.255.0  broadcast 192.168.42.255
        ...
virbrDocker: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.123.1  netmask 255.255.255.0  broadcast 192.168.123.255
        inet6 2001:db8:ca2:2::1  prefixlen 64  scopeid 0x0<global>
        ...

On the host, upon the regular interfaces, we can see the two bridges for the two virtual networks:

virbrDocker: That is the virtual network that we created in libvirt. This is connected to the host network with NAT. We assigned these IP addresses, when we defined the network.
virbr1: That is the host-only virtual network that was created out-of-the-box. This one has no internet access.

Interface the new VM

You can log in to the newly created VM with the docker-machine ssh <machine_name> command On the newly created docker ready VM, four interfaces were created.

# docker-machine ssh manager
                        ##         .
                  ## ## ##        ==
               ## ## ## ## ##    ===
           /"""""""""""""""""\___/ ===
      ~~~ {~~ ~~~~ ~~~ ~~~~ ~~~ ~ /  ===- ~~~
           \______ o           __/
             \    \         __/
              \____\_______/
 _                 _   ____     _            _
| |__   ___   ___ | |_|___ \ __| | ___   ___| | _____ _ __
| '_ \ / _ \ / _ \| __| __) / _` |/ _ \ / __| |/ / _ \ '__|
| |_) | (_) | (_) | |_ / __/ (_| | (_) | (__|   <  __/ |
|_.__/ \___/ \___/ \__|_____\__,_|\___/ \___|_|\_\___|_|
Boot2Docker version 18.05.0-ce, build HEAD : b5d6989 - Thu May 10 16:35:28 UTC 2018
Docker version 18.05.0-ce, build f150324

Check the interfaces of the new VM:

docker@manager:~$ ifconfig
docker0   inet addr:172.17.0.1  Bcast:172.17.255.255  Mask:255.255.0.0
          ...
eth0      inet addr:192.168.123.195  Bcast:192.168.123.255  Mask:255.255.255.0
          ...
eth1      inet addr:192.168.42.118  Bcast:192.168.42.255  Mask:255.255.255.0

eth0:192.168.123.195 - Interface to the new virtual network (docker-network) created by us. this network is connected to the host network,so it has public internet access as well.
eth1:192.168.42.118 - This connect to the dynamically created host-only virtual network. Just for VM-to-VM communication
docker0:172.17.0.1 - This VM is ment to host docker container, so the docker daemon was already installed and started on it. Form docker point of view, this VM is also a (docker) host, and therefore the docker daemon created the default virtual bridge, that the containers will be connected to unless it is specified implicitly otherwise during container creation.

Inspect the new VM with the docker-machine inspect command

# docker-machine inspect manager
{
    "ConfigVersion": 3,
    "Driver": {
        ....
        "CPU": 1,
        "Network": "docker-network",
        "PrivateNetwork": "docker-machines",
        "ISO": "/root/.docker/machine/machines/manager/boot2docker.iso",
        "...
    },
    "DriverName": "kvm",
    "HostOptions": {
       ....
        },
        "SwarmOptions": {
            "IsSwarm": false,
            ...
        },
        "AuthOptions": {
           ....
        }
    },
    "Name": "manager"
}

Routing table

All the packages that ment to go to the docker VMs are routed to the bridges
# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
...
192.168.42.0    0.0.0.0         255.255.255.0   U     0      0        0 virbr1  <<<<this
192.168.123.0   0.0.0.0         255.255.255.0   U     0      0        0 virbrDocker  <<<this

Docker

Contents