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

Example: <xterm>

NAME   = test-vm
MEMORY = 128 

CPU    = 1

</xterm>

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 : <xterm> OS = [ kernel = /vmlinuz,

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

</xterm>

The disks of a VM are defined with the DISK vector attribute. You can define as many DISK attributes as you need. There are two special disk types that are created on-the-fly in the target resource: swap and fs. 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 three disks: the base system attached to sda1, a clean filesystem attached to sda2, and a swap partition attached to sda3. Note that fs and swap are generated on-the-fly: <xterm> DISK = [ source = /images/vm.img,

       clone    = no,
       target   = sda1,
       readonly = no]

DISK = [ type = fs,

       size   = 4096,
       format = ext3,
       save   = yes,
       target = sda2]

DISK = [ type = swap,

       size   = 2048,
       target = sda3]

</xterm>

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: <xterm> NIC = [ network = “Public” ]

NIC = [ MAC = “00:11:22:33:44:55”

      bridge = eth0 ]

</xterm>

For more information on setting up virtual networks please check the Managing Virtual Networks guide.

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: <xterm> GRAPHICS = [

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

</xterm>

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: <xterm> REQUIREMENTS = “CPUSPEED > 1000” RANK = FREECPU </xterm>

Context information is passed to the Virtual Machine via an ISO mounted as a partition. This information can be defined in the VM template in the optional section called Context, with the following attributes:

The values referred to by VARIABLE can be:

• $<template_variable>: any single value variable of the VM template, like for example $NAME
• $<template_variable>[<attribute>]: Any single value contained in a multiple value variable in the VM template, like for example $NIC[IP].
• $<template_variable>[<attribute>, <attribute2>=<value2>]: Any single value contained in a multiple value variable in the VM template, setting one atribute to discern between multiple variables called the same way, like for example $NIC[IP, NETWORK=“Private LAN”].
• $<vm_id>.<context_var>: Any $<template_variable> (expressed in any of the previous ways) pertaining to VM with id=<vm_id>, like for example $4.$NAME, referring to the NAME of the VM with ID=4.

Example: <xterm> CONTEXT = [

hostname   = "$NAME",
ip_private = "$NIC[IP, NETWORK=\"Private LAN\"]",
ip_gen     = "10.0.0.$VMID"]

</xterm>

The syntax of the requirement expressions is defined as:

<xterm>

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

</xterm>

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 work 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

If using OpenNebula's default match-making scheduler in a hypervisor heterogeneous environment, it is a good idea to add an extra line like the following to the VM template to ensure its placement in a VMWare hypervisor enabled machine.

<xterm> REQUIREMENTS=“HYPERVISOR=\”vmware\“” </xterm>

Examples:

<xterm>

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

</xterm>

The syntax of the rank expressions is defined as:

<xterm>

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

</xterm>

Rank expressions are evaluated using each host information. '+', '-', '*', '/' and '-' are arithmetic operators. The rank expression is calculated using floating point arithmetics, and then round to an integer value.

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 number (integer or float) attribute defined for the host can be used in the rank attribute

Examples:

<xterm>

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

</xterm>

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.

Example <xterm>

RAW = [

    type  = "xen",
    data  = "builder=\"linux\"
             bootloader=\"/usr/lib/xen/boot/domUloader.py\"
             bootargs=\"--entry=xvda2:/boot/vmlinuz-xenpae,/boot/vmlinuz-xenpae\""]

</xterm>