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 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 chinaeast location.

az group create --name myResourceGroup --location chinaeast

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: