To add a new driver to OpenNebula some lines should be added to /etc/one/oned.conf to describe it:

IM_MAD = [
    name       = "<im name>",
    executable = "one_im_ssh",
    arguments  = "-r 0 -t 15 <driver name>" ]

Usually the im name and driver name are the same. The im name is the name we will use to refer in the cli to that driver, for example, to set this driver for a host. The driver name will be used to refer to the directory in /var/lib/one/remotes/im. For example, to refer the remotes directory kvm.d the driver name should be kvm.

The executable one_im_ssh is the driver server that executes the probes in the remote host, in case we want to execute the probes in the frontend we can substitute it by one_im_sh.

These im server takes some parameters, these are the most common:

An IM diver is composed of one or several scripts that write to stdout information in this form:

KEY1="value1"
KEY2="value2"

These scripts should be stored in a directory called <name of the driver>.d located in /var/lib/one/remotes/im. The scripts should be executable and can be written in any language but make sure that the hosts or the frontend have everything it needs to run them. For example, if the script is written in python you need the interpreter and all the libraries needed installed in the hosts.

The drivers receive three parameters in case they need them:

Take into account that in shell script the parameters start at 1 ($1) and in ruby start at 0 (ARGV[0]). For shell script you can use this snippet to get the parameters:

hypervisor  = $1
host_id     = $2
host_name   = $3

You can add any key and value you want to use later in RANK and REQUIREMENTS for scheduling but there are some basic values you should output:

For example, a probe that gets memory information about a host could be something like:

#!/bin/bash
 
total=$(free | awk ' /^Mem/ { print $2 }')
used=$(free | awk '/buffers\/cache/ { print $3 }')
free=$(free | awk '/buffers\/cache/ { print $4 }')
 
echo "TOTALMEMORY=$total"
echo "USEDMEMORY=$used"
echo "FREEMEMORY=$free"

Executing it should give use memory values:

<xterm> $ ./memory_probe TOTALMEMORY=1020696 USEDMEMORY=209932 FREEMEMORY=810724 </xterm>

For real examples check the directories at /var/lib/one/remotes/im.

The scripts should also provide information about the VMs running in the host. This is useful as it will only need one call to gather all that information about the VMs in each host. The output should be in this form:

VM_POLL=YES
VM=[
  ID=86,
  DEPLOY_ID=one-86,
  POLL="USEDMEMORY=918723 USEDCPU=23 NETTX=19283 NETRX=914 STATE=a" ]
VM=[
  ID=645,
  DEPLOY_ID=one-645,
  POLL="USEDMEMORY=563865 USEDCPU=74 NETTX=2039847 NETRX=2349923 STATE=a" ]

The first line (VM_POLL=YES) is used to indicate OpenNebula that VM information will follow. Then the information about the VMs is output in that form.

For example here is a simple script to get qemu/kvm VMs status from libvirt. As before, check the scripts from OpenNebula for a complete example:

#!/bin/bash
 
echo "VM_POLL=YES"
 
virsh -c qemu:///system list | grep one- | while read vm; do
    deploy_id=$(echo $vm | cut -d' ' -f 2)
    id=$(echo $deploy_id | cut -d- -f 2)
    status_str=$(echo $vm | cut -d' ' -f 3)
 
    if [ $status_str == "running" ]; then
        state="a"
    else
        state="e"
    fi
 
    echo "VM=["
    echo "  ID=$id,"
    echo "  DEPLOY_ID=$deploy_id,"
    echo "  POLL=\"STATE=$state\" ]"
done

<xterm> $ ./vm_poll VM_POLL=YES VM=[

ID=0,
DEPLOY_ID=one-0,
POLL="STATE=a" ]

VM=[

ID=1,
DEPLOY_ID=one-1,
POLL="STATE=a" ]

</xterm>