Create a highly available VM

Article
02/27/2017

This script sample creates everything needed to run several Ubuntu virtual machines configured in a highly available and load balanced configuration. After running the script, you will have three virtual machines, joined to an Azure Availability Set, and accessible through an Azure Load Balancer.

To run this sample, install the latest version of the Azure CLI. To start, run az login to create a connection with Azure.

Samples for the Azure CLI are written for the bash shell. To run this sample in Windows PowerShell or Command Prompt, you may need to change elements of the script.

If you don't have an Azure subscription, create a free account before you begin.

Sample script

#!/bin/bash
# Passed validation in Cloud Shell on 3/3/2022

# <FullScript>
# Load balance traffic to VMs for high availability

# Variable block
let "randomIdentifier=$RANDOM*$RANDOM"
location="East US"
resourceGroup="msdocs-load-balancer-rg-$randomIdentifier"
tag="create-vm-nlb"
vNet="msdocs-vnet-lb-$randomIdentifier"
subnet="msdocs-subnet-lb-$randomIdentifier"
loadBalancerPublicIp="msdocs-public-ip-lb-$randomIdentifier"
loadBalancer="msdocs-load-balancer-$randomIdentifier"
frontEndIp="msdocs-front-end-ip-lb-$randomIdentifier"
backEndPool="msdocs-back-end-pool-lb-$randomIdentifier"
probe80="msdocs-port80-health-probe-lb-$randomIdentifier"
loadBalancerRuleWeb="msdocs-load-balancer-rule-port80-$randomIdentifier"
loadBalancerRuleSSH="msdocs-load-balancer-rule-port22-$randomIdentifier"
networkSecurityGroup="msdocs-network-security-group-lb-$randomIdentifier"
networkSecurityGroupRuleSSH="msdocs-network-security-rule-port22-lb-$randomIdentifier"
networkSecurityGroupRuleWeb="msdocs-network-security-rule-port80-lb-$randomIdentifier"
nic="msdocs-nic-lb-$randomIdentifier"
availabilitySet="msdocs-availablity-set-lb-$randomIdentifier"
vm="msdocs-vm-lb-$randomIdentifier"
image="Ubuntu2204"
ipSku="Standard"
login="azureuser"

# Create a resource group
echo "Creating $resourceGroup in "$location"..."
az group create --name $resourceGroup --location "$location" --tags $tag

# Create a virtual network and a subnet.
echo "Creating "
az network vnet create --resource-group $resourceGroup --location "$location" --name $vNet --subnet-name $subnet

# Create a public IP address for load balancer.
echo "Creating $loadBalancerPublicIp"
az network public-ip create --resource-group $resourceGroup --name $loadBalancerPublicIp

# Create an Azure Load Balancer.
echo "Creating $loadBalancer with $frontEndIP and $backEndPool"
az network lb create --resource-group $resourceGroup --name $loadBalancer --public-ip-address $loadBalancerPublicIp --frontend-ip-name $frontEndIp --backend-pool-name $backEndPool

# Create an LB probe on port 80.
echo "Creating $probe80 in $loadBalancer"
az network lb probe create --resource-group $resourceGroup --lb-name $loadBalancer --name $probe80 --protocol tcp --port 80

# Create an LB rule for port 80.
echo "Creating $loadBalancerRuleWeb for $loadBalancer"
az network lb rule create --resource-group $resourceGroup --lb-name $loadBalancer --name $loadBalancerRuleWeb --protocol tcp --frontend-port 80 --backend-port 80 --frontend-ip-name $frontEndIp --backend-pool-name $backEndPool --probe-name $probe80

# Create three NAT rules for port 22.
echo "Creating three NAT rules named $loadBalancerRuleSSH"
for i in `seq 1 3`; do
  az network lb inbound-nat-rule create --resource-group $resourceGroup --lb-name $loadBalancer --name $loadBalancerRuleSSH$i --protocol tcp --frontend-port 422$i --backend-port 22 --frontend-ip-name $frontEndIp
done

# Create a network security group
echo "Creating $networkSecurityGroup"
az network nsg create --resource-group $resourceGroup --name $networkSecurityGroup

# Create a network security group rule for port 22.
echo "Creating $networkSecurityGroupRuleSSH in $networkSecurityGroup for port 22"
az network nsg rule create --resource-group $resourceGroup --nsg-name $networkSecurityGroup --name $networkSecurityGroupRuleSSH --protocol tcp --direction inbound --source-address-prefix '*' --source-port-range '*'  --destination-address-prefix '*' --destination-port-range 22 --access allow --priority 1000

# Create a network security group rule for port 80.
echo "Creating $networkSecurityGroupRuleWeb in $networkSecurityGroup for port 22"
az network nsg rule create --resource-group $resourceGroup --nsg-name $networkSecurityGroup --name $networkSecurityGroupRuleWeb --protocol tcp --direction inbound --priority 1001 --source-address-prefix '*' --source-port-range '*' --destination-address-prefix '*' --destination-port-range 80 --access allow --priority 2000

# Create three virtual network cards and associate with public IP address and NSG.
echo "Creating three NICs named $nic for $vNet and $subnet"
for i in `seq 1 3`; do
  az network nic create --resource-group $resourceGroup --name $nic$i --vnet-name $vNet --subnet $subnet --network-security-group $networkSecurityGroup --lb-name $loadBalancer --lb-address-pools $backEndPool --lb-inbound-nat-rules $loadBalancerRuleSSH$i
done
   
# Create an availability set.
echo "Creating $availabilitySet"
az vm availability-set create --resource-group $resourceGroup --name $availabilitySet --platform-fault-domain-count 3 --platform-update-domain-count 3

# Create three virtual machines, this creates SSH keys if not present.
echo "Creating three VMs named $vm with $nic using $image"
for i in `seq 1 3`; do
  az vm create --resource-group $resourceGroup --name $vm$i --availability-set $availabilitySet --nics $nic$i --image $image --public-ip-sku $ipSku  --admin-username $login --generate-ssh-keys --no-wait
done

# List the virtual machines
az vm list --resource-group $resourceGroup
# </FullScript>

# echo "Deleting all resources"
# az group delete --name $resourceGroup -y

Clean up deployment

Run the following command to remove the resource group, VM, and all related resources.

az group delete --name myResourceGroup

Script explanation

This script uses the following commands to create a resource group, virtual machine, availability set, load balancer, and all related resources. Each command in the table links to command specific documentation.

Command	Notes
az group create	Creates a resource group in which all resources are stored.
az network vnet create	Creates an Azure virtual network and subnet.
az network public-ip create	Creates a public IP address with a static IP address and an associated DNS name.
az network lb create	Creates an Azure Network Load Balancer (NLB).
az network lb probe create	Creates an NLB probe. An NLB probe is used to monitor each VM in the NLB set. If any VM becomes inaccessible, traffic is not routed to the VM.
az network lb rule create	Creates an NLB rule. In this sample, a rule is created for port 80. As HTTP traffic arrives at the NLB, it is routed to port 80 of one of the VMs in the NLB set.
az network lb inbound-nat-rule create	Creates an NLB Network Address Translation (NAT) rule. NAT rules map a port of the NLB to a port on a VM. In this sample, a NAT rule is created for SSH traffic to each VM in the NLB set.
az network nsg create	Creates a network security group (NSG), which is a security boundary between the internet and the virtual machine.
az network nsg rule create	Creates an NSG rule to allow inbound traffic. In this sample, port 22 is opened for SSH traffic.
az network nic create	Creates a virtual network card and attaches it to the virtual network, subnet, and NSG.
az vm availability-set create	Creates an availability set. Availability sets ensure application uptime by spreading the virtual machines across physical resources such that if failure occurs, the entire set is not effected.
az vm create	Creates the virtual machine and connects it to the network card, virtual network, subnet, and NSG. This command also specifies the virtual machine image to be used and administrative credentials.
az group delete	Deletes a resource group including all nested resources.

Next steps

For more information on the Azure CLI, see Azure CLI documentation.

Additional virtual machine CLI script samples can be found in the Azure Linux VM documentation.

Create a highly available VM

Sample script

Clean up deployment

Script explanation

Next steps

Additional resources