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Use cloud-init to set hostname for a Linux VM in Azure

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Applies to: ✔️ Linux VMs ✔️ Flexible scale sets

This article shows you how to use cloud-init to configure a specific hostname on a virtual machine (VM) or virtual machine scale sets (VMSS) at provisioning time in Azure. These cloud-init scripts run on first boot once the resources have been provisioned by Azure. For more information about how cloud-init works natively in Azure and the supported Linux distros, see cloud-init overview

Set the hostname with cloud-init

By default, the hostname is the same as the VM name when you create a new virtual machine in Azure. To run a cloud-init script to change this default hostname when you create a VM in Azure with az vm create, specify the cloud-init file with the --custom-data switch.

To see upgrade process in action, create a file in your current shell named cloud_init_hostname.txt and paste the following configuration. For this example, create the file in the Cloud Shell not on your local machine. You can use any editor you wish. Make sure that the whole cloud-init file is copied correctly, especially the first line.

#cloud-config
fqdn: myhostname

Before deploying this image, you need to create a resource group with the az group create command. An Azure resource group is a logical container into which Azure resources are deployed and managed. The following example creates a resource group named myResourceGroup in the eastus location.

az group create --name myResourceGroup --location eastus

Now, create a VM with az vm create and specify the cloud-init file with --custom-data cloud_init_hostname.txt as follows:

az vm create \
  --resource-group myResourceGroup \
  --name vmName \
  --image imageCIURN \
  --custom-data cloud_init_hostname.txt \
  --generate-ssh-keys

Note

Replace myResourceGroup, vmName, and imageCIURN values accordingly. Make sure an image with Cloud-init is chosen.

Once created, the Azure CLI shows information about the VM. Use the publicIpAddress to SSH to your VM. Enter your own address as follows:

ssh <user>@<publicIpAddress>

To see the VM name, use the hostname command as follows:

sudo hostname

The VM should report the hostname as that value set in the cloud-init file, as shown in the following example output:

myhostname

Next steps

For additional cloud-init examples of configuration changes, see the following: