A Virtual Machine within the OpenNebula system consists of:

• A capacity in terms memory and CPU
• A set of NICs attached to one or more virtual networks
• A set of disk images. In general it could be necessary to transfer some of these image files to/from the execution host.
• A state file (optional) or recovery file, that contains the memory image of a running VM plus some hypervisor specific information.

The above items, plus some additional VM attributes like the OS kernel, are specified in a VM template file.

Each VM in OpenNebula is identified by an unique number, the <VID>. Also, the user can assign it a name in the VM template, the default name for each VM is one-<VID>.

The life-cycle of a virtual machine within the system includes the following stages (note that this is a simplified version):

• Pending (pend): By default a VM starts in the pending state, waiting for a resource to run on.

• Hold (hold): The owner has held the VM and it will not be scheduled until it is released.

• Prolog (prol): The system is transferring the VM files (disk images and the recovery file).

• Running (runn): The VM is running (note that this stage includes booting and shutting down phases). In this state, the virtualization driver will periodically monitor it.

• Migrate (migr): The VM is migrating from one resource to another. This can be a life migration or cold migration (the VM is saved and VM files are transferred to the new resource).

• Epilog (epil): In this phase the system clean ups the cluster node used to host the VM, and additionally disk images to be saved are copied back to the cluster front-end.

• Stopped (stop): The VM is stopped. VM state has been saved and it has been transferred back along with the disk images.

• Suspended (susp): Same as stopped, but the files are left in the remote resource to later restart the VM there (i.e. there is no need to re-schedule the VM).

• Failed (fail): The VM failed.

• Done (done): The VM is done. VMs in this state wont be shown with “onevm list” but are kept in the database for accounting purposes.

In order to use OpenNebula, you need to set the following variables in your environment. You may want to place them, in the .bashrc of the <oneadmin> account for commodity:

A template file consists of a set of attributes that defines a Virtual Machine. The syntax of the template file is as follows:

• Anything behind the pound sign (#) is a comment.
• Strings can be delimited with double quotes (“), if the a double quote is part of the string you can use single quotes (').
• Single Attributes are in the form:

NAME=VALUE

• Vector Attributes that contain several values can be defined as follows:

NAME=[NAME1=VALUE1,NAME2=VALUE2...]

OpenNebula templates were designed to be hypervisor-agnostic, but still there are some peculiarities to be taken into account, and mandatory attributes change depending on the target hypervisor. Hypervisor specific information for this attributes can be found in the drivers configuration guides, here listed in.

OpenNebula has been designed to be easily extended, so any attribute name can be defined for later use in any OpenNebula module. There are some pre-defined attributes, though.

The following attributes can be defined to specified the capacity of a VM.

Example:

  NAME   = test-vm

  CPU    = 1
  MEMORY = 128 

The OS system is defined with the OS vector attribute. The following sub-attributes are supported:

Note the hypervisor column states that the attribute is Optional, Mandatory, or - not supported for that hypervisor

(*) Xen needs a kernel or a bootloader to be specified. If both are set in the template, the kernel boot method will be used.

Example, a VM booting from sda1 with kernel /vmlinuz :

OS = [ kernel     = /vmlinuz,
       initrd     = /initrd.img,
       root       = sda1,
       kernel_cmd = "ro xencons=tty console=tty1"]

The disks of a VM are defined with the DISK vector attribute. You can define as many DISK attributes as you need. The following sub-attributes for DISK are supported:

Note the hypervisor column states that the attribute is Optional, Mandatory, or - not supported for that hypervisor

Example, a VM with two disks the base system attached to sda1, and the other a swap partition generated on-the-fly attached to sda2:

DISK = [ source   = /images/vm.img,
         clone    = no,
         target   = sda1,
         readonly = no]

DISK = [ type   = swap,
         size   = 2048,
         target = sda2]

For more information on image management and moving please check the Storage guide.

Each network interface of a VM is defined with the NIC vector attribute. You can define as many NIC attributes as you need. The following sub-attributes for NIC are supported:

Note the hypervisor column states that the attribute is Optional, Mandatory, or - not supported for that hypervisor

Example, a VM with two NIC attached to two different networks, one make use of the Virtual Network Manager lease feature:

NIC = [ network = "Public" ]

NIC = [ MAC    = "00:11:22:33:44:55"
        bridge = eth0 ]

For more information on setting up virtual networks please check the Networking guide. Also you may be interested in how to set up your VMs to make use of this feature.

The following I/O interfaces can be defined for a VM:

Note the hypervisor column states that the attribute is Optional, Mandatory, or - not supported for that hypervisor

Example:

GRAPHICS = [ 
  type    = "vnc",              
  listen  = "127.0.0.1",
  port    = "5"]

Note For KVM hypervisor the port number is a real one, not the VNC port. So for VNC port 0 you should specify 5900, for port 1 is 5901 and so on.

The following attributes placement constraints and preferences for the VM:

Note the hypervisor column states that the attribute is Optional, Mandatory, or - not supported for that hypervisor

Example:

REQUIREMENTS = "CPUSPEED > 1000"
RANK         = FREECPU

The syntax of the requirement expressions is defined as:

  stmt::= expr';'
  expr::= VARIABLE '=' NUMBER
        | VARIABLE '!''=' NUMBER
        | VARIABLE '>' NUMBER
        | VARIABLE '<' NUMBER
        | VARIABLE '=' STRING
        | VARIABLE '!''=' STRING
        | expr '&' expr
        | expr '|' expr
        | '!' expr
        | '(' expr ')'

Each expression is evaluated to 1 (TRUE) or 0 (FALSE). Only those hosts for which the requirement expression is evaluated to TRUE will be considered to run the VM.

Logical operators are as expected ( less '<', greater '>', '&' AND, '|' OR, '!' NOT), '=' means equals with numbers (floats and integers). When you use '=' operator with strings, it performs a shell wildcard pattern matching.

Any variable defined by the Information Manager driver can be used in the requirements. Check the configuration guide to find out how to extend the information model

There are some predefined variables that can be used: HOSTNAME, TOTALCPU, TOTALMEMORY, FREEMEMORY, FREECPU, USEDMEMORY, USEDCPU, HYPERVISOR

Examples:

  REQUIREMENTS = "HOSTNAME = \"aquila*\"" #Only aquila nodes, note the quotes
  REQUIREMENTS = FREECPU > 0.6            #Only those resources with more than 60% of free CPU

The syntax of the rank expressions is defined as:

stmt::= expr';'
expr::= VARIABLE
      | INTEGER
      | expr '+' expr
      | expr '-' expr
      | expr '*' expr
      | expr '/' expr
      | '-' expr
      | '(' expr ')'

Rank expressions are evaluated using each host information. '+', '-', '*', '/' and '-' are arithmetic operators, so only integer values should be used in rank expressions.

The rank expression is evaluated for each host, those hosts with a higher rank are used first to start the VM. The rank policy must be implemented by the scheduler. Check the configuration guide to configure the scheduler.

Similar to the requirements attribute, any integer attribute defined for the host can be used in the rank attribute

Examples:

RANK = FREECPU                     # First those resources with a higher Free CPU
RANK = FREECPU * 100 - TEMPERATURE # Consider also the CPU temperature

This optional section of the VM template is used whenever the need to pass special attributes to the underlying hypervisor arises. Anything placed in the data attribute gets passed straight to the hypervisor, unmodified.

For example, the following template defines a VM with 512MB of memory and one CPU. The VM has two disks: sda supported by an image file; and sdb (a swap partition). Only one NIC is defined with a predefined MAC address. In this case, between all the suitable hosts (those that meets CPU and MEMORY requirements, and also CPUSPEED > 1000 requirement), OpenNebula will pick the host with more free CPU.

#---------------------------------------
# VM definition example
#---------------------------------------

NAME = vm-example 

CPU    = 1
MEMORY = 512

# --- kernel & boot device ---

OS = [
  kernel   = "/vmlinuz",
  initrd   = "/initrd.img",
  root     = "sda" ]

# --- 2 disks ---

DISK = [
  source   = "/local/xen/domains/etch/disk.img",
  target   = "sda",
  readonly = "no" ]

DISK = [
  type     = swap,
  size     = 1024
  target   = "sdb",
  readonly = "no" ]

# --- 1 NIC ---

NIC = [ mac="00:ff:72:17:20:27"]

# --- VNC server ---

GRAPHICS = [ 
  type    = "vnc",              
  listen  = "127.0.0.1",
  port    = "5"]

# Scheduling Attributes for the rank policy

REQUIREMENTS = "CPUSPEED > 1000"
RANK         = FREECPU

Note that you can add as many DISK and NIC attributes as you need

OpenNebula comes with a rich command line interface intended for users and sysadmins fond of consoles. There are commands to manage the three basic aspects of OpenNebula: virtual machines, hosts and virtual networks.

A complete reference for these three commands can be found here. The following subsections show the basics of the available commands with simple usage exmaples.

This command enables virtual machine management. Actions offered are:

• create ( a VM in OpenNebula's VM pool )
• deploy (on a particular cluster node)
• shutdown
• livemigrate (the virtual machine is transferred between cluster nodes with no noticeable downtime)
• migration (machine gets stopped and resume elsewhere)
• hold
• release (from hold state)
• stop (virtual machine state is transferred back to OpenNebula for a possible reschedule)
• cancel
• suspend (virtual machine state is left in the cluster node for resuming)
• resume
• delete
• list (outputs all the available VMs)
• show (outputs information for a specific VM)
• top (lists VMs continously)
• history (gets VMs history of execution on the cluster nodes)

Assuming we have a VM template called myVM.one describing a virtual machine. Then, we can allocate the VM in OpenNebula issuing a:

$ onevm create myVM.one

afterwards, the VM can be listed with the list option:

$ onevm list
  ID     NAME STAT CPU     MEM        HOSTNAME        TIME
   0   myVM   runn   0 2097152            ursa 00 00:00:07

and details about it can be obtained with show:

$ onevm show myVM
VID            : 0                   
UID            : 0                   
STATE          : ACTIVE              
LCM STATE      : RUNNING             
DEPLOY ID      : one-0               
MEMORY         : 2097152             
CPU            : 0                   
LAST POLL      : 1228318438          
START TIME     : 03/25 18:17:09      
STOP TIME      : 01/01 01:00:00       
NET TX         : 0                   
NET RX         : 0                   

....: Template :....
    CPU             : 1                   
    DISK            : CLONE=no,READONLY=no,SOURCE=/images/myVM/myVM.img,TARGET=hda
    DISK            : SIZE=1024,TARGET=hdb,TYPE=swap
    MEMORY          : 2048                
    NAME            : myVM              
    NIC             : BRIDGE=eth1,IP=147.96.81.252,MAC=00:02:93:60:51:fc,NETWORK=myNetwork,VNID=0
    OS              : BOOT=hd,INITRD=/initrd.img,KERNEL=/vmlinuz,KERNEL_CMD=ro,ROOT=sda

This command enables cluster nodes management. Actions offered are:

• create ( a node in OpenNebula's host pool )
• show (details of a particular cluster node)
• delete
• list (lists nodes in the host pool)
• enable
• disable
• top (lists host continuously)

Assuming a cluster node called hosts01 running the XEN hypervisor and without shared folders, we can let OpenNebula know about it using:

$ onehost create host01 im_xen vmm_xen tm_ssh

then we can list the recently added node:

$ onehost list
 HID NAME                      RVM   TCPU   FCPU   ACPU    TMEM    FMEM STAT
   5 ursa05                      3    800    766    500 8387584 6157312   on

and retrieve more detailed information for this node using show:

$ onehost show host01
HID      = 0
HOSTNAME = host01
IM MAD   = im_xen
VMM MAD  = vmm_xen
TM MAD   = tm_ssh
MANAGED  = 1
ATTRIBUTES

        ARCH=x86_64
        CPUSPEED=1995
        FREECPU=766
        FREEMEMORY=6157312
        HOSTNAME=host01
        MODELNAME=Intel(R) Xeon(R) CPU           L5335  @ 2.00GHz
        NETRX=26008308
        NETTX=7961198
        TOTALCPU=800
        TOTALMEMORY=8387584
        USEDCPU=34
        USEDMEMORY=2230272
HOST SHARES
        HID          = 5
        ENDPOINT     = 
        MAX_CPU      = 800
        MAX_MEMORY   = 8387584
        MAX_DISK     = 0
        CPU_USAGE    = 300
        MEMORY_USAGE = 1572864
        DISK_USAGE   = 0
        RUNNING_VMS  = 0

This command enables the management of virtual networks. Actions offered are:

• create ( a virtual network in OpenNebula's VN pool )
• show (details of a particular virtual network)
• delete
• list (lists all the VNs in the VN pool)

Assuming a virtual network template called myVN.net, we can create the virtual network within OpenNebula issuing:

$ onevnet create myVN.net

and then list it using:

$ onevnet list
 NID NAME            TYPE   BRIDGE
   0 myVN               1   eth1  

and obtain details about it with:

$ onevnet show 0
NID               : 0
UID               : 0
Network Name      : myVN
Type              : Fixed
Size              : 10
Bridge            : eth1

....: Template :....
        BRIDGE=eth1
        LEASES=IP=147.96.80.143
        NAME=myVN
        TYPE=FIXED

....: Leases :....
IP = 147.96.80.143  MAC = 00:02:93:60:50:8f  USED = 0 VID = -1

OpenNebula can be used to deploy different solutions for on-demand execution of services. We have prepared the following use cases to illustrate its functionality in typical computing scenarios:

• On-demand Scaling of Computing Clusters
• On-demand Infrastructure for Training
• Scaling out Computing Clusters to Amazon EC2
• Scaling out Web Servers to Amazon EC2