NixOS has some work-in-progress support for running OpenStack Compute (also known as Nova), an infrastructure-as-a-service cloud computing platform. It's currently limited to running all of Nova on a single machine, so it's mostly useful for experimentation.

Contents

edit Enabling Nova

Add the following to your configuration.nix: 

virtualisation.nova.enableSingleNode = true;

and run nixos-rebuild switch. This will enable several daemons:

  • nova-api is the API server that receives and executes requests from cloud users, e.g. to start, query or terminate virtual machines.
  • nova-objectstore is a simple disk image server. It serves images placed in /var/lib/nova/images/.
  • nova-scheduler schedules VM execution requests and hands them over to a nova-compute node.
  • nova-network manages networks and allocates IP addresses.
  • nova-compute starts and manages virtual machines. It downloads disk images from nova-objectstore.
  • libvirtd is the low-level daemon responsible for running and managing virtual machines.
  • rabbitmq is a messaging protocol used by the various Nova components to communicate with each other.

edit Configuring and testing Nova

You can now create a user with administrative privileges: 

$ nova-manage user admin eelco
2011-04-07 12:57:23,806 AUDIT nova.auth.manager [-] Created user eelco (admin: True)

You should also create a range of IP addresses that can be assigned to VMs: 

$ nova-manage network create 10.0.0.0/8 1 32

Nova will set up iptables rules to perform NAT on these addresses automatically.

You should also create a project. In Nova, VMs are always associated with a project, which can have multiple users. To create a project test with eelco as owner: 

$ nova-manage project create test eelco
2011-04-07 13:03:01,404 AUDIT nova.auth.manager [-] Created project test with manager eelco

Tools such as euca2ools, which allow you to perform operations on the cloud, require a number of environment variables containing stuff such as credentials and the URL of the API server. To obtain the necessary environment variables for a specific project and user: 

$ nova-manage project environment test eelco

This create a file ./novarc, which you can source from your shell (e.g. source ./novarc). The important variables are: 

export EC2_ACCESS_KEY="72389c9d-...:test"
export EC2_SECRET_KEY="6c145c32-..."
export EC2_URL="http://192.168.1.20:8773/services/Cloud"

Next we'll get a small VM images so that we can run a VM. 

$ cd /var/lib/nova/images
$ curl http://images.ansolabs.com/tty.tgz | tar xvfzo -
$ nova-manage image convert /var/lib/nova/images

Check that Nova can see the images: 

$ euca-describe-images 
IMAGE   ami-tty demo/tty        admin   available       public          x86_64  machine aki-tty ari-tty
IMAGE   aki-tty nova/tty-kernel admin   available       public          x86_64  kernel           
IMAGE   ari-tty nova/tty-ramdisk        admin   available       public          x86_64  ramdisk

To log in to VMs via SSH, you'll need to generate an SSH key pair. The VM will receive the public key on startup, while you get the private key to log in. 

$ euca-add-keypair my_key > my_key
$ chmod 600 my_key

Now we can start a VM: 

$ euca-run-instances -k my_key ami-tty
RESERVATION     r-ngnfe3x6      test    default
INSTANCE        i-00000007      ami-tty                 scheduling      my_key (test, None)     2011-04-07 12:50:19.155448      None    None

After a while, if everything works out, the VM will start. You can get its IP address using euca-describe-instances: 

$ euca-describe-instances i-00000007
RESERVATION     r-ngnfe3x6      test    default
INSTANCE        i-00000007      ami-tty 10.0.0.3        10.0.0.3        running         my_key (test, stan)     0       m1.small        2011-04-07 12:50:19.155448      nova

So we can now log in using the SSH key generated above: 

$ ssh -i ./my_key 10.0.0.3
...
# uname -a
Linux ttylinux_host 2.6.35-22-virtual #35-Ubuntu SMP Sat Oct 16 23:19:29 UTC 2010 x86_64 GNU/Linux

edit Running NixOS

Of course you'll want to run NixOS VMs in your private cloud. This requires building a NixOS disk image. 

$ NIXOS_CONFIG=/etc/nixos/nixos/modules/virtualisation/nova-config.nix \
    nix-build /etc/nixos/nixos/ -A config.system.build.novaImage

You can (sort of) test whether the VM works by running qemu-img create ./image -b ./result/image -f qcow2; qemu-kvm -nographic ./image.

Now make the image available: 

$ mkdir /var/lib/nova/images/ami-nixos
$ cp ./result/image /var/lib/nova/images/ami-nixos/

and create a file /var/lib/nova/images/ami-nixos/info.json with the following contents: 

{
    "imageId": "ami-nixos",
    "imageLocation": "nixos/nixos",
    "imageOwnerId": "eelco",
    "imageState": "available",
    "type": "machine",
    "isPublic": true,
    "architecture": "x86_64"
}

You can then start a NixOS VM as follows: 

$ euca-run-instances -k my_key ami-nixos

Once the VM is running, you should be able to log in via SSH. For information on using the VM, see NixOS on Amazon EC2.

edit To Do

  • Support running Nova components on multiple machines (especially nova-compute).
  • Use MySQL instead of SQLite.
  • Don't use RabbitMQ's guest user.
  • Don't run everything as root.
Retrieved from "http://nixos.org/wiki/NixOS_and_OpenStack_Compute"