Using cloud-init with AHV command line

TL;DR

  • Using cloud-init with AHV is conceptually identical to using KVM/QEMU- we need to use a few different tools with AHV
  • You will need a Linux image that is configured to use cloud-init. A good source is cloud-images.ubuntu.com
  • We will create a cloud-init textual file and create a mountable version using the cloud-localds tool on a Linux host
  • We will attach the cloud-init enabled ubuntu image and our cloud-init customization file to the VM at boot time
  • At boottime ubuntu will access the cloud-init data mounted as a CDROM and do the customization for us
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AHV Tip: Shutdown multiple VMs in parallel

Often in my lab I want to shutdown a large number of VMs quickly. In the example below I submit the power-off command for a maximum of 50 VMs in parallel. Be aware that we’re using the command line, and in line with true Unix philosophy the OS will assume we know what we are doing and obey us completely and immediately. In other words pasting the below commands to your CVM will immediately shutdown all powered on VMs.

 for i in $(acli  vm.list power_state=on | awk '{ print $(NF) }' |tail -50); do acli vm.off $i &  done

How to deploy Ubuntu cloud images to Nutanix AHV

In this example we use the KVM cloud image from the Canonical Ubuntu image repository. More information on Ubuntu cloud images is on the canonical cloud image page. More detail on the cloud image boot process and cloud-init here: Ubuntu UEC/Imanges.

We can use the Ubuntu cloud image catalog, and specifically use one that has been built to run on KVM. Since AHV is based on KVM/QEMU Nutanix can use that image format directly without any further conversion.

Using a cloud image can be a quicker way to stand up a particular version of Linux without having to go through the Linux installation process (choosing usernames, keyboard types, timezones etc.). However, you will need to pass in a public key so that you can login to the instance once it has booted.

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Install a bitnami image to Nutanix AHV cluster.

One of the nice things about using public cloud is the ability to use pre-canned application virtual appliances created by companies like Bitnami.

We can use these same appliance images on Nutanix AHV to easily do a Postgres database benchmark

Step 1. Get the bitnami image

wget  https://bitnami.com/redirect/to/587231/bitnami-postgresql-11.3-0-r56-linux-debian-9-x86_64.zip

Step 2. Unzip the file and convert the bitnami vmdk images to a single qcow2[1] file.

qemu-img convert *vmdk bitnami.qcow2

Put the bitnami.qcow2 image somewhere accessible to a browser, connected to the Prism service, then upload using the “Image Configuration”

Once the image is uploaded, it’s time to create a new VM based on that image

Once booted, you’ll see the bitnami logo and you can configure the bitnami passwords, enable ssh etc. using the console.

Enable/disable ssh in bitnami images
Connecting to Postgres in bitnami images
Note – when you “sudo -c postgres <some-psql-tool> the password it is asking for is the Postgres DB password (stored in ./bitnami-credentials) not any unix user password.

Once connected to the appliance we can use postgres and pgbench to generate simplistic database workload.

[1] Do this on a Linux box somewhere. For some reason the conversion failed using my qemu utilities installed via brew. Importing OVAs direct into AHV should be available in the future.