Installing Ubuntu Precise Server On A Xen Server Hypervisor

Recently, I had to install a vm on a xenserver hypervisor which I had locally. I intended to use this vm as a platform for my devstack setup with xenserver.

Along the way, I had to tweak lot of parameters in the VM to get this working. So, I thought of scripting this entire process out. Here is the script I used.

#!/bin/bash
if [ $# -ne 2 ]; then
   echo "Usage: $0 <vm-name-label> <ram-size-in-bytes>"
   exit
fi

#Create ubuntu precise template if does not exist

TEMPLATE_EXISTS=`xe template-list name-label="Ubuntu Precise (64-bit)" params=uuid --minimal`

if [ "$TEMPLATE_EXISTS" == "" ]; then

    TEMPLATE_UUID=`xe template-list \
            name-label="Ubuntu Lucid Lynx 10.04 (64-bit)" params=uuid --minimal`
    NEW_TEMPLATE_UUID=`xe vm-clone uuid=$TEMPLATE_UUID \
            new-name-label="Ubuntu Precise (64-bit)"`
    xe template-param-set other-config:default_template=true \
            other-config:debian-release=precise uuid=$NEW_TEMPLATE_UUID

fi

#Create a VM with the new template

VM_UUID=`xe vm-install new-name-label="$1" template="Ubuntu Precise (64-bit)"`

#Create network interfaces for this VM

XEN_NET_UUID=`xe network-list params=uuid bridge=xenbr0 --minimal`
xe vif-create network-uuid=${XEN_NET_UUID} vm-uuid=${VM_UUID} device=0
xe vm-param-set other-config:install-repository="http://archive.ubuntu.com/ubuntu/ubuntu/" uuid=${VM_UUID}
xe vm-param-set other-config:disable_pv_vnc=true uuid=${VM_UUID}
xe vm-memory-limits-set dynamic-max=$2 dynamic-min=$2 static-max=$2 static-min=$2 uuid=${VM_UUID}

echo "Starting VM with uuid ${VM_UUID}"
xe vm-start uuid=${VM_UUID}

Creating a cell environment using devstack

Recently, I stumbled upon a task to create an openstack setup using devstack in a cell environment.

I am assuming that reader is familiar with openstack and devstack.

The idea I started, with was to have a VM, running nova-api, nova-cell, glance and keystone services.

I created two more VMs on two different XenServer hyervisors to be children cells.

Each child runs nova-cell, nova-compute, nova-network, nova-scheduler and nova-conductor services.

Below are the steps I followed in parent and children to get this working.

Parent

1. Download Devstack

git clone https://github.com/openstack-dev/devstack
 
2. I had to tweak localrc a bit before stack-up to enable nova-cells. My localrc contained,

enable_service n-cell n-api-meta
disable_service n-cpu, n-net, n-sch

3. Run ./stack.sh. Once stack.sh completed, I tweaked /etc/nova/nova.conf to include

[cells]
enable=True
name=api
cell_type=api

3. nova-api has to be restarted.

Children

1. Download devstack

git clone https://github.com/openstack-dev/devstack

2. Tweak localrc to contain below content,

enable_service n-cell
disable_service n-api, key, g-api

3. Run ./stack.sh

4. Tweak /etc/nova/nova.conf

[DEFAULT]

#Disable quota checking in child cells. Let API cell do it exclusively.
quota_driver=nova.quota.NoopQuotaDriver
glance_api_servers=<glance server of parent>

[cells]
enable=True
name=cell1
cell_type=compute

Notice, that I am telling child to use glance server running in parent.

On a side note, these are the essential settings in nova.conf for a compute node on XenServer,

compute_driver = xenapi.XenAPIDriver
firewall_driver = nova.virt.firewall.IptablesFirewallDriver 
xenapi_connection_password = ROOT PASSWORD FOR HYPERISOR
xenapi_connection_username = root
xenapi_connection_url = http://HYPERVISOR_IP 

Cell Creation 

After this set-up, I had to hook up parent cell and children cells together

On parent, run this,

1. nova-manage cell create --name=cell1 --cell_type=child --username=guest --password=password --hostname=<child ip> --port=5672 --virtual_host=/ --woffset=1.0 --wscale=1.0 

2. Restart n-cell

On Child, run this,

1. nova-manage cell create --name=parent --cell_type=parent --username=guest --password=password --hostname=<parent ip> --port=5672 --virtual_host=/ --woffset=1.0 --wscale=1.0

2. Restart n-cell.

After this, if you tail logs for n-cell in parents and cell, you should be able to see children trying to update the parent with their capabilities. This concludes your cell set-up.