Book of AOS
Nutanix Guest Tools (NGT)
Nutanix Guest Tools (NGT) is a software based in-guest agent framework which enables advanced VM management functionality through the Nutanix Platform.
The solution is composed of the NGT installer which is installed on the VMs and the Guest Tools Framework which is used for coordination between the agent and Nutanix platform.
The NGT installer contains the following components:
- Guest Agent Service
- Self-service Restore (SSR) aka File-level Restore (FLR) CLI
- VM Mobility Drivers (VirtIO drivers for AHV)
- VSS Agent and Hardware Provider for Windows VMs
- App Consistent snapshot support for Linux VMs (via scripts to quiesce)
This framework is composed of a few high-level components:
- Guest Tools Service
- Gateway between the AOS and Nutanix services and the Guest Agent. Distributed across CVMs within the cluster with an elected NGT Leader which runs on the current Prism Leader (hosting cluster vIP)
- Guest Agent
- Agent and associated services deployed in the VM’s OS as part of the NGT installation process. Handles any local functions (e.g. VSS, Self-service Restore (SSR), etc.) and interacts with the Guest Tools Service.
The figure shows the high-level mapping of the components:
Guest Tools Mapping
Guest Tools Service
The Guest Tools Service is composed of two main roles:
- NGT Leader
- Handles requests coming from NGT Proxy and interfaces with AOS components. A single NGT Leader is dynamically elected per cluster; in the event the current leader fails a new one will be elected. The service listens internally on port 2073.
- NGT Proxy
- Runs on every CVM and will forward requests to the NGT Leader to perform the desired activity. The current VM acting as the Prism Leader (hosting the VIP) will be the active CVM handling communication from the Guest Agent. Listens externally on port 2074.
Current NGT Leader
You can find the IP of the CVM hosting the NGT Leader role with the following command (run on any CVM):
The figure shows the high-level mapping of the roles:
Guest Tools Service
The Guest Agent is composed of the following high-level components as mentioned prior:
Communication and Security
The Guest Agent Service communicates with Guest Tools Service via the Nutanix Cluster IP using SSL. For deployments where the Nutanix cluster components and UVMs are on a different network (hopefully all), ensure that the following are possible:
- Ensure routed communication from UVM network(s) to Cluster IP
- Create a firewall rule (and associated NAT) from UVM network(s) allowing communication with the Cluster IP on port 2074 (preferred)
The Guest Tools Service acts as a Certificate Authority (CA) and is responsible for generating certificate pairs for each NGT enabled UVM. This certificate is embedded into the ISO which is configured for the UVM and used as part of the NGT deployment process. These certificates are installed inside the UVM as part of the installation process.
NGT Agent Installation
NGT Agent installation can be performed via Prism or CLI/Scripts (ncli/REST/PowerShell).
To install NGT via Prism, navigate to the ‘VM’ page, select a VM to install NGT on and click ‘Enable NGT’:
Enable NGT for VM
Click ‘Yes’ at the prompt to continue with NGT installation:
Enable NGT Prompt
The VM must have a CD-ROM as the generated installer containing the software and unique certificate will be mounted there as shown:
Enable NGT - CD-ROM
The NGT installer CD-ROM will be visible in the OS:
Enable NGT - CD-ROM in OS
Double click on the CD to begin the installation process.
You can perform a silent installation of the Nutanix Guest Tools by running the following command (from CD-ROM location):
Follow the prompts and accept the licenses to complete the installation:
Enable NGT - Installer
As part of the installation process Python, PyWin and the Nutanix Mobility (cross-hypervisor compatibility) drivers will also be installed.
After the installation has been completed, a reboot will be required.
After successful installation and reboot, you will see the following items visible in ‘Programs and Features’:
Enable NGT - Installed Programs
Services for the NGT Agent and VSS Hardware Provider will also be running:
Enabled NGT - Services
NGT is now installed and can be leveraged.
Bulk NGT Deployment
Rather than installing NGT on each individual VM, it is possible to embed and deploy NGT in your base image.
Follow the following process to leverage NGT inside a base image:
- Install NGT on leader VM and ensure communication
- Clone VMs from leader VM
Mount NGT ISO on each clone (required to get new certificate pair)
- Example: ncli ngt mount vm-id=<CLONE_ID> OR via Prism
- Automated way coming soon :)
- Power on clones
When the cloned VM is booted it will detect the new NGT ISO and copy relevant configuration files and new certificates and will start communicating with the Guest Tools Service.
Nutanix provides native OS customization capabilities leveraging CloudInit and Sysprep. CloudInit is a package which handles bootstrapping of Linux cloud servers. This allows for the early initialization and customization of a Linux instance. Sysprep is a OS customization for Windows.
Some typical uses include:
- Setting Hostname
- Installing packages
- Adding users / key management
- Custom scripts
The solution is applicable to Linux guests running on AHV, including versions below (list may be incomplete, refer to documentation for a fully supported list):
- Operating Systems:
- Linux - most modern distributions
- Windows - most modern distributions
In order for CloudInit to be used the following are necessary:
- CloudInit package must be installed in Linux image
Sysprep is available by default in Windows installations.
CloudInit can be installed (if not already) using the following commands:
Red Hat Based Systems (CentOS, RHEL)
Debian Based Systems (Ubuntu)
Sysprep is part of the base Windows installation.
To leverage a custom script for OS customization, a check box and inputs is available in Prism or the REST API. This option is specified during the VM creation or cloning process:
Custom Script - Input Options
Nutanix has a few options for specifying the custom script path:
- ADSF Path
- Use a file which has been previously upload to ADSF
- Upload a file
- Upload a file which will be used
- Type or paste script
- CloudInit script or Unattend.xml text
Nutanix passes the user data script to CloudInit or Sysprep process during first boot by creating a CD-ROM which contains the script. Once the process is complete we will remove the CD-ROM.
The platform supports a good amount of user data input formats, I’ve identified a few of the key ones below:
User-Data Script (CloudInit - Linux)
A user-data script is a simple shell script that will be executed very late in the boot process (e.g. “rc.local-like”).
The scripts will begin similar to any bash script: “#!”.
Below we show an example user-data script:
Include File (CloudInit - Linux)
The include file contains a list of urls (one per line). Each of the URLs will be read and they will be processed similar to any other script.
The scripts will begin with: “#include”.
Below we show an example include script:
Cloud Config Data (CloudInit - Linux)
The cloud-config input type is the most common and specific to CloudInit.
The scripts will begin with: “#cloud-config”
Below we show an example cloud config data script:
Validating CloudInit Execution
CloudInit log files can be found in /var/log/cloud-init.log and cloud-init-output.log.
Unattend.xml (Sysprep - Windows)
The unattend.xml file is the input file Sysprep uses for image customization on boot, you can read more here: LINK
The scripts will begin with: “<?xml version=”1.0” ?>”.
Below we show an example unattend.xml file:
Karbon (Container Services)
Nutanix provides the ability to leverage persistent containers on the Nutanix platform using Kubernetes (currently). It was previously possible to run Docker on Nutanix platform; however, data persistence was an issue given the ephemeral nature of containers.
Container technologies like Docker are a different approach to hardware virtualization. With traditional virtualization each VM has its own Operating System (OS) but they share the underlying hardware. Containers, which include the application and all its dependencies, run as isolated processes that share the underlying Operating System (OS) kernel.
The following table shows a simple comparison between VMs and Containers:
|Metric||Virtual Machines (VM)||Containers|
|Virtualization Type||Hardware-level virtualization||OS kernel virtualization|
|Provisioning Speed||Slower (seconds to minutes)||Real-time / fast (us to ms)|
|Performance Overhead||Limited performance||Native performance|
|Security||Fully isolated (more secure)||Process-level isolation (less secure)|
The solution is applicable to the configurations below (list may be incomplete, refer to documentation for a fully supported list):
- Docker 1.13
*As of 4.7, the solution only supports storage integration with Docker based containers. However, any other container system can run as a VM on the Nutanix platform.
Container Services Constructs
The following entities compose Karbon Container Services:
- Nutanix Docker Machine Driver: Handles Docker container host provisioning via Docker Machine and the AOS Image Service
- Nutanix Docker Volume Plugin: Responsible for interfacing with AOS Volumes to create, mount, format and attach volumes to the desired container
The following entities compose Docker (note: not all are required):
- Docker Image: The basis and image for a container
- Docker Registry: Holding space for Docker Images
- Docker Hub: Online container marketplace (public Docker Registry)
- Docker File: Text file describing how to construct the Docker image
- Docker Container: Running instantiation of a Docker Image
- Docker Engine: Creates, ships and runs Docker containers
- Docker Swarm: Docker host clustering / scheduling platform
- Docker Daemon: Handles requests from Docker Client and does heavy lifting of building, running and distributing containers
- Docker Store: Marketplace for trusted and enterprise ready containers
The Nutanix solution currently leverages Docker Engine running in VMs which are created using Docker Machine. These machines can run in conjunction with normal VMs on the platform.
Docker - High-level Architecture
Nutanix has developed a Docker Volume Plugin which will create, format and attach a volume to container(s) using the AOS Volumes feature. This allows the data to persist as a container is power cycled / moved.
Data persistence is achieved by using the Nutanix Volume Plugin which will leverage AOS Volumes to attach a volume to the host / container:
Docker - Volumes
In order for Container Services to be used the following are necessary:
- Nutanix cluster must be AOS 4.7 or later
- A CentOS 7.0+ or a Rhel 7.2+ OS image with the iscsi-initiator-utils package installed must be downloaded and exist as an image in the AOS Image Service
- The Nutanix Data Services IP must be configured
- Docker Toolbox must be installed on the client machine used for configuration
- Nutanix Docker Machine Driver must be in client’s PATH
Docker Host Creation
Assuming all pre-requisites have been met the first step is to provision the Nutanix Docker Hosts using Docker Machine:
The following figure shows a high-level overview of the backend workflow:
Docker - Host Creation Workflow
The next step is to SSH into the newly provisioned Docker Host(s) via docker-machine ssh:
To install the Nutanix Docker Volume Plugin run:
After that runs you should now see the plugin enabled:
Docker Container Creation
Once the Nutanix Docker Host(s) have been deployed and the volume plugin has been enabled, you can provision containers with persistent storage.
A volume using the AOS Volumes can be created using the typical Docker volume command structure and specifying the Nutanix volume driver. Example usage below:
The following command structure can be used to create a container using the created volume. Example usage below:
The following figure shows a high-level overview of the backend workflow:
Docker - Container Creation Workflow
You now have a container running with persistent storage!