Vagrant Libvirt Provider

This is a Vagrant 1.4.3+ plugin that adds an Libvirt provider to Vagrant, allowing Vagrant to control and provision machines via Libvirt toolkit.

Note: Actual version (0.0.15) is still a development one. Feedback is welcome and can help a lot :-)

Features (Version 0.0.13)

• Controll local Libvirt hypervisors.
• Vagrant up, destroy, suspend, resume, halt, ssh, reload and provision commands.
• Upload box image (qcow2 format) to Libvirt storage pool.
• Create volume as COW diff image for domains.
• Create private networks.
• Create and boot Libvirt domains.
• SSH into domains.
• Setup hostname and network interfaces.
• Provision domains with any built-in Vagrant provisioner.
• Synced folder support via rsync or nfs.
• Snapshots via sahara
• Use boxes from other Vagrant providers via vagrant-mutate

Future work

• More boxes should be available.
• Take a look at open issues.

Installation

Install using standard Vagrant 1.4.3+ plugin installation methods. After installing, vagrant up and specify the libvirt provider. An example is shown below.

$ vagrant plugin install vagrant-libvirt

Possible problems with plugin installation on Linux

In case of problems with building nokogiri and ruby-libvirt gem, install missing development libraries for libxslt, libxml2 and libvirt.

In Ubuntu, Debian, ...

$ sudo apt-get install libxslt-dev libxml2-dev libvirt-dev

In RedHat, Centos, Fedora, ...

# yum install libxslt-devel libxml2-devel libvirt-devel

Vagrant Project Preparation

After installing the plugin (instructions above), the quickest way to get started is to add Libvirt box and specify all the details manually within a config.vm.provider block. So first, add Libvirt box using any name you want. This is just an example of Libvirt CentOS 6.4 box available:

$ vagrant box add centos64 http://kwok.cz/centos64.box

And then make a Vagrantfile that looks like the following, filling in your information where necessary. In example below, VM named test_vm is created from centos64 box and setup with 10.20.30.40 IP address.

Vagrant.configure("2") do |config|

  # If you are still using old centos box, you have to setup root username for
  # ssh access. Read more in section 'SSH Access To VM'.
  config.ssh.username = "root"

  config.vm.define :test_vm do |test_vm|
    test_vm.vm.box = "centos64"
    test_vm.vm.network :private_network, :ip => '10.20.30.40'
  end

  config.vm.provider :libvirt do |libvirt|
    libvirt.driver = "qemu"
    libvirt.host = "localhost"
    libvirt.connect_via_ssh = true
    libvirt.username = "root"
    libvirt.storage_pool_name = "default"
  end
end

Libvirt Configuration Options

This provider exposes quite a few provider-specific configuration options:

• driver - A hypervisor name to access. For now only qemu is supported.
• host - The name of the server, where libvirtd is running.
• connect_via_ssh - If use ssh tunnel to connect to Libvirt.
• username - Username and password to access Libvirt.
• password - Password to access Libvirt.
• id_ssh_key_file - The id ssh key file name to access Libvirt (eg: id_dsa or id_rsa or ... in the user .ssh directory)
• storage_pool_name - Libvirt storage pool name, where box image and instance snapshots will be stored.

Domain Specific Options

• disk_bus - The type of disk device to emulate. Defaults to virtio if not set. Possible values are documented in libvirt's description for target.
• memory - Amount of memory in MBytes. Defaults to 512 if not set.
• cpus - Number of virtual cpus. Defaults to 1 if not set.
• nested - Enable nested virtualization. Default is false.
• cpu_mode - What cpu mode to use for nested virtualization. Defaults to 'host-model' if not set.
• volume_cache - Controls the cache mechanism. Possible values are "default", "none", "writethrough", "writeback", "directsync" and "unsafe". See driver->cache in libvirt documentation.
• kernel - To launch the guest with a kernel residing on host filesystems (Equivalent to qemu -kernel)
• initrd - To specify the initramfs/initrd to use for the guest (Equivalent to qemu -initrd)
• cmd_line - Arguments passed on to the guest kernel initramfs or initrd to use (Equivalent to qemu -append)

Specific domain settings can be set for each domain separately in multi-VM environment. Example below shows a part of Vagrantfile, where specific options are set for dbserver domain.

Vagrant.configure("2") do |config|
  config.vm.define :dbserver do |dbserver|
    dbserver.vm.box = "centos64"
    dbserver.vm.provider :libvirt do |domain|
      domain.memory = 2048
      domain.cpus = 2
      domain.nested = true
      domain.volume_cache = 'none'
    end
  end

  # ...

Create Project - Vagrant up

In prepared project directory, run following command:

$ vagrant up --provider=libvirt

Vagrant needs to know that we want to use Libvirt and not default VirtualBox. That's why there is --provider=libvirt option specified. Other way to tell Vagrant to use Libvirt provider is to setup environment variable export VAGRANT_DEFAULT_PROVIDER=libvirt.

How Project Is Created

Vagrant goes through steps below when creating new project:

1. Connect to Libvirt localy or remotely via SSH.
2. Check if box image is available in Libvirt storage pool. If not, upload it to remote Libvirt storage pool as new volume.
3. Create COW diff image of base box image for new Libvirt domain.
4. Create and start new domain on Libvirt host.
5. Check for DHCP lease from dnsmasq server.
6. Wait till SSH is available.
7. Sync folders via rsync and run Vagrant provisioner on new domain if setup in Vagrantfile.

Networks

Networking features in the form of config.vm.network support private networks concept.

Public Network interfaces are currently implemented using the macvtap driver. The macvtap driver is only available with the Linux Kernel version >= 2.6.24. See the following libvirt documentation for the details of the macvtap usage.

http://www.libvirt.org/formatdomain.html#elementsNICSDirect

An examples of network interface definitions:

  # Private network
  config.vm.define :test_vm1 do |test_vm1|
    test_vm1.vm.network :private_network, :ip => "10.20.30.40"
  end

  # Public Network
  config.vm.define :test_vm1 do |test_vm1|
    test_vm1.vm.network :public_network, :dev => "eth0", :mode => 'bridge'
  end

In example below, one network interface is configured for VM test_vm1. After you run vagrant up, VM will be accessible on IP address 10.20.30.40. So if you install a web server via provisioner, you will be able to access your testing server on http://10.20.30.40 URL. But beware that this address is private to libvirt host only. It's not visible outside of the hypervisor box.

If network 10.20.30.0/24 doesn't exist, provider will create it. By default created networks are NATed to outside world, so your VM will be able to connect to the internet (if hypervisor can). And by default, DHCP is offering addresses on newly created networks.

The second interface is created and bridged into the physical device 'eth0'. This mechanism uses the macvtap Kernel driver and therefore does not require an existing bridge device. This configuration assumes that DHCP and DNS services are being provided by the public network. This public interface should be reachable by anyone with access to the public network.

Private Network Options

Note: These options are not applicable to public network interfaces.

There is a way to pass specific options for libvirt provider when using config.vm.network to configure new network interface. Each parameter name starts with 'libvirt__' string. Here is a list of those options:

• :libvirt__network_name - Name of libvirt network to connect to. By default, network 'default' is used.
• :libvirt__netmask - Used only together with :ip option. Default is '255.255.255.0'.
• :libvirt__dhcp_enabled - If DHCP will offer addresses, or not. Used only when creating new network. Default is true.
• :libvirt__adapter - Number specifiyng sequence number of interface.
• :libvirt__forward_mode - Specify one of none, nat or route options. This option is used only when creating new network. Mode none will create isolated network without NATing or routing outside. You will want to use NATed forwarding typically to reach networks outside of hypervisor. Routed forwarding is typically useful to reach other networks within hypervisor. By default, option nat is used.
• :libvirt__forward_device - Name of interface/device, where network should be forwarded (NATed or routed). Used only when creating new network. By default, all physical interfaces are used.
• :mac - MAC address for the interface.

Public Network Options

• :dev - Physical device that the public interface should use. Default is 'eth0'
• :mode - The mode in which the public interface should operate in. Supported modes are available from the libvirt documentation. Default mode is 'bridge'.
• :mac - MAC address for the interface.

Management Network

Vagrant-libvirt uses a private network to perform some management operations on VMs. All VMs will have an interface connected to this network and an IP address dynamically assigned by libvirt. This is in addition to any networks you configure. The name and address used by this network are configurable at the provider level.

• management_network_name - Name of libvirt network to which all VMs will be connected. If not specified the default is 'vagrant-libvirt'.
• management_network_address - Address of network to which all VMs will be connected. Must include the address and subnet mask. If not specified the default is '192.168.121.0/24'.

You may wonder how vagrant-libvirt knows the IP address a VM received. Libvirt doesn't provide a standard way to find out the IP address of a running domain. But we do know the MAC address of the virtual machine's interface on the management network. Libvirt is closely connected with dnsmasq, which acts as a DHCP server. dnsmasq writes lease information in the /var/lib/libvirt/dnsmasq directory. Vagrant-libvirt looks for the MAC address in this file and extracts the corresponding IP address.

SSH Access To VM

There are some configuration options for ssh access to VM via config.ssh.* in Vagrantfile. Untill provider version 0.0.5, root user was hardcoded and used to access VMs ssh. Now, vagrant user is used by default, but it's configurable via config.ssh.username option in Vagrantfile now.

If you are still using CentOS 6.4 box from example in this README, please set ssh username back to root, because user vagrant is not usable (I forgot to add necessary ssh key to his authorized_keys).

Configurable ssh parameters in Vagrantfile after provider version 0.0.5 are:

• config.ssh.username - Default is username vagrant.
• config.ssh.guest_port - Default port is set to 22.
• config.ssh.forward_agent - Default is false.
• config.ssh.forward_x11 - Default is false.

Forwarded Ports

vagrant-libvirt supports Forwarded Ports via ssh port forwarding. For each forwarded_port directive you specify in your Vagrantfile, vagrant-libvirt will maintain an active ssh process for the lifetime of the VM.

Synced Folders

There is minimal support for synced folders. Upon vagrant up, the Libvirt provider will use rsync (if available) to uni-directionally sync the folder to the remote machine over SSH.

This is good enough for all built-in Vagrant provisioners (shell, chef, and puppet) to work!

If used options :nfs => true, folder will exported by nfs.

Box Format

You can view an example box in the example_box/directory. That directory also contains instructions on how to build a box.

The box is a tarball containing:

• qcow2 image file named box.img.
• metadata.json file describing box image (provider, virtual_size, format).
• Vagrantfile that does default settings for the provider-specific configuration for this provider.

Development

To work on the vagrant-libvirt plugin, clone this repository out, and use Bundler to get the dependencies:

$ git clone https://github.com/pradels/vagrant-libvirt.git
$ cd vagrant-libvirt
$ bundle install

Once you have the dependencies, verify the unit tests pass with rake:

$ bundle exec rake

If those pass, you're ready to start developing the plugin. You can test the plugin without installing it into your Vagrant environment by just creating a Vagrantfile in the top level of this directory (it is gitignored) that uses it. Don't forget to add following line at the beginning of your Vagrantfile while in development mode:

Vagrant.require_plugin "vagrant-libvirt"

Now you can use bundler to execute Vagrant:

$ bundle exec vagrant up --provider=libvirt

IMPORTANT NOTE: bundle is crucial. You need to use bundled vagrant.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request