Revision as of 22:05, 22 June 2018

Manage Virtual Hosts with docker-machine

Introduction

https://docs.docker.com/machine/overview/ Docker Machine is a tool that lets you install Docker Engine on virtual hosts, and manage the hosts with docker-machine commands. You can use Machine to create Docker hosts on your local Mac or Windows box, on your company network, in your data center, or on cloud providers like Azure, AWS, or Digital Ocean.

Using docker-machine commands, you can start, inspect, stop, and restart a managed host, upgrade the Docker client and daemon, and configure a Docker client to talk to your host.

When people say “Docker” they typically mean Docker Engine, the client-server application made up of the Docker daemon, a REST API that specifies interfaces for interacting with the daemon, and a command line interface (CLI) client that talks to the daemon (through the REST API wrapper). Docker Engine accepts docker commands from the CLI, such as docker run <image>, docker ps to list running containers, docker image ls to list images, and so on.

Docker Machine is a tool for provisioning and managing your Dockerized hosts (hosts with Docker Engine on them). Typically, you install Docker Machine on your local system. Docker Machine has its own command line client docker-machine and the Docker Engine client, docker. You can use Machine to install Docker Engine on one or more virtual systems. These virtual systems can be local (as when you use Machine to install and run Docker Engine in VirtualBox on Mac or Windows) or remote (as when you use Machine to provision Dockerized hosts on cloud providers). The Dockerized hosts themselves can be thought of, and are sometimes referred to as, managed “machines”.

Hypervisor drivers

What is a driver

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

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

The default value of the driver parameter is "virtualbox".

docker-machine can create and manage virtual hosts on the local machine and on remote clouds. Always the chosen driver determines where and how the virtual machine will be created. The guest operating system that is being installed on the new machine is also determined by the hypervisor driver. E.g. with the "virtualbox" driver you can create machines locally using the boot2docker as the guest OS.

The driver also determines the virtual network types and interfaces types that are created inside the virtual machine. E.g. the KVM driver creates two virtual networks (bridges), one host-global and one host-private network.

In the docker-machine create command, the available driver options are also determined by the driver. You always has to check the available options at the vandor of driver. For cloud drivers typical options are the remote url, the login name and the password. Some driver allows to change the guest OS, the CPU number or the default memory.

Here is a complete list of the currently available drivers: https://github.com/docker/docker.github.io/blob/master/machine/AVAILABLE_DRIVER_PLUGINS.md

KVM driver

KVM driver home page: https://github.com/dhiltgen/docker-machine-kvm

Minimum Parameters:

--driver 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.

Images:
By default docker-machine-kvm uses a boot2docker.iso as guest os for the kvm hypervisior. It's also possible to use every guest os image that is derived from boot2docker.iso as well. For using another image use the --kvm-boot2docker-url parameter.

Dual Network:

eth1 - A host private network called docker-machines is automatically created to ensure we always have connectivity to the VMs. The docker-machine ip command will always return this IP address which is only accessible from your local system.
eth0 - You can specify any libvirt named network. If you don't specify one, the "default" named network will be used.

If you have exotic networking topolgies (openvswitch, etc.), you can use virsh edit mymachinename after creation, modify the first network definition by hand, then reboot the VM for the changes to take effect. Typically this would be your "public" network accessible from external systems To retrieve the IP address of this network, you can run a command like the following: docker-machine ssh mymachinename "ip -one -4 addr show dev eth0|cut -f7 -d' '"

Driver Parameters:

--kvm-cpu-count Sets the used CPU Cores for the KVM Machine. Defaults to 1 .
--kvm-disk-size Sets the kvm machine Disk size in MB. Defaults to 20000 .
--kvm-memory Sets the Memory of the kvm machine in MB. Defaults to 1024.
--kvm-network Sets the Network of the kvm machinee which it should connect to. Defaults to default.
--kvm-boot2docker-url Sets the url from which host the image is loaded. By default it's not set.
--kvm-cache-mode Sets the caching mode of the kvm machine. Defaults to default.
--kvm-io-mode-url Sets the disk io mode of the kvm machine. Defaults to threads.

Install softwares

First we have to install the docker-machine app itself:

base=https://github.com/docker/machine/releases/download/v0.14.0 &&
  curl -L $base/docker-machine-$(uname -s)-$(uname -m) >/tmp/docker-machine &&
  sudo install /tmp/docker-machine /usr/local/bin/docker-machine

Secondly we have to install the hypervisor driver for the docker-machine to be able to create, manage Virtual Machines running on the hypervisor. As we are going to use the KVM hypervisor, we have to install the "docker-machine-driver-kvm" driver:

# curl -Lo docker-machine-driver-kvm \
  https://github.com/dhiltgen/docker-machine-kvm/releases/download/v0.7.0/docker-machine-driver-kvm \
  && chmod +x docker-machine-driver-kvm \
  && sudo mv docker-machine-driver-kvm /usr/local/bin

We suppose that KVM and the libvirt is already installed on the system.

Tip
If you want to use VirtualBox as your hypervisor, no extra steps are needed, as its docker-machine driver is included in the docker-machine app

Available 3rd party drivers:
https://github.com/docker/docker.github.io/blob/master/machine/AVAILABLE_DRIVER_PLUGINS.md

Create machines with KVM

Create the machine

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.

# 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 management 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

IPtables modifications

-A POSTROUTING -s 192.168.123.0/24 -d 224.0.0.0/24 -j RETURN
-A POSTROUTING -s 192.168.123.0/24 -d 255.255.255.255/32 -j RETURN
-A POSTROUTING -s 192.168.123.0/24 ! -d 192.168.123.0/24 -p tcp -j MASQUERADE --to-ports 1024-65535
-A POSTROUTING -s 192.168.123.0/24 ! -d 192.168.123.0/24 -p udp -j MASQUERADE --to-ports 1024-65535
-A POSTROUTING -s 192.168.123.0/24 ! -d 192.168.123.0/24 -j MASQUERADE
<pre>

<pre>
-A INPUT -i virbr1 -p udp -m udp --dport 53 -j ACCEPT
-A INPUT -i virbr1 -p tcp -m tcp --dport 53 -j ACCEPT
-A INPUT -i virbr1 -p udp -m udp --dport 67 -j ACCEPT
-A INPUT -i virbr1 -p tcp -m tcp --dport 67 -j ACCEPT
-A INPUT -i virbrDocker -p udp -m udp --dport 53 -j ACCEPT
-A INPUT -i virbrDocker -p tcp -m tcp --dport 53 -j ACCEPT
-A INPUT -i virbrDocker -p udp -m udp --dport 67 -j ACCEPT
-A INPUT -i virbrDocker -p tcp -m tcp --dport 67 -j ACCEPT

-A OUTPUT -o virbr1 -p udp -m udp --dport 68 -j ACCEPT
-A OUTPUT -o virbrDocker -p udp -m udp --dport 68 -j ACCEPT

-A FORWARD -i virbr1 -o virbr1 -j ACCEPT
-A FORWARD -o virbr1 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -i virbr1 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -d 192.168.123.0/24 -o virbrDocker -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -s 192.168.123.0/24 -i virbrDocker -j ACCEPT
-A FORWARD -i virbrDocker -o virbrDocker -j ACCEPT
-A FORWARD -o virbrDocker -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -i virbrDocker -j REJECT --reject-with icmp-port-unreachable

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Revision as of 22:05, 22 June 2018

Contents

Manage Virtual Hosts with docker-machine

Introduction

Hypervisor drivers

What is a driver

KVM driver

Install softwares

Create machines with KVM

Create the machine

Check what was created

Interfaces on the host

Interface the new VM

Routing table

IPtables modifications

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