Nimbus/Alamo Updates

qcow2 images on Nimbus/Alamo 

Support for the qcow2 virtual machine image format has been added to Nimbus on Alamo. One feature of qcow2 is that the size of an image on disk grows only as data is added to it. This is in contrast to a raw image file that is of a fixed size (the size of the virtual disk) which we typically gzip to reduce storage space.

One of the benefits of using qcow2 images is that Nimbus does not have to perform a gzip or gunzip step when running and saving virtual machines. This reduces the time to start and save virtual machines significantly. We will be adding qcow2 images for Linux distributions over time. If you wish to use specific distributions/versions, please let us know. An important note is that the qcow2 images provided by some distributions (e.g. Ubuntu, Fedora), don't work well out of the box with Nimbus. The reason for this is that while Nimbus adds your ssh key to the root account of the virtual machine, these images do not allow direct login to the root account (they expect you to log in to a normal user account such as ubuntu or ec2-user and then use sudo).

Nimbus/Alamo networking improvements

The network device used by Nimbus virtual machines on Alamo has been changed from Realtek RTL-8139 to Virtio. After this change, our measurements show that network bandwidth to and from Nimbus virtual machines has improved by a factor of 3 or more. The Virtio device is supported by all of the existing virtual machine images that we tested. Your virtual machines should automatically detect this new device and benefit from the higher networking bandwidth. If you have any problems with networking on your virtual machines, please submit a ticket.

Nimbus/Alamo authentication changes

Due to the expiration of a CA certificate, the Nimbus services on Alamo are now using a new host certificate from a different certificate authority. We apologize for the inconvenience, but this will require that you make some changes to your Nimbus client to continue to use Alamo. The first change is to use a Nimbus cloud client that includes the CA certificates associated with our new Nimbus certificate. One way to accomplish this is to download the Nimbus cloud client version 022. An alternative is to modify your existing cloud client by manually adding the CA certificates to it. This can be accomplished by:

1. Download the InCommon Server CA certificate and save it as nimbus-cloud-client-021/lib/certs/84df5188.0 
2. Go to the Comodo AddTrust page and download the AddTrust External CA Root certificate. Save it as nimbus-cloud-client-021/lib/certs/3c58f906.0 

The second change is to modify your nimbus-cloud-client-022/conf/alamo.conf file to have the DN of the new certificate, like so:

•  vws.factory.identity=/C=US/2.5.4.17=78711/ST=TX/L=Austin/2.5.4.9=1 University Station/O=The University of Texas at Austin/OU=TACC - Texas Advanced Computing Center/CN=nimbus.futuregrid.tacc.utexas.edu 

 If you encounter any problems using Nimbus on Alamo, please submit a ticket for assistance.