There are several ways to create a virtual machine (VM) in Azure:
If you already have a virtual hard disk (VHD) to use or you want to copy the VHD from an existing VM to use, you can create a new VM by attaching the VHD to the new VM as an OS disk.
You can create a new VM from the VHD of a VM that has been deleted. For example, if you have an Azure VM that isn't working correctly, you can delete the VM and use its VHD to create a new VM. You can either reuse the same VHD or create a copy of the VHD by creating a snapshot and then creating a new managed disk from the snapshot. Although creating a snapshot takes a few more steps, it preserves the original VHD and provides you with a fallback.
Take a classic VM and use the VHD to create a new VM that uses the Resource Manager deployment model and managed disks. For the best results, Stop the classic VM in the Azure portal before creating the snapshot.
You can create an Azure VM from an on-premises VHD by uploading the on-premises VHD and attaching it to a new VM. You use PowerShell or another tool to upload the VHD to a storage account, and then you create a managed disk from the VHD.
When you use a specialized disk to create a new VM, the new VM retains the computer name of the original VM. Other computer-specific information (e.g. CMID) is also kept and, in some cases, this duplicate information could cause issues. When copying a VM, be aware of what types of computer-specific information your applications rely on.
Thus, don't use a specialized disk if you want to create multiple VMs. Instead, for larger deployments, create an image and then use that image to create multiple VMs.
Creating a VM from a disk:
We assume you have the managed disk VHD that you want to use, now you can create the VM in the portal following below steps:
Go to the Azure portal and on the left menu select All services.
In the All services search box, enter disks and then select Disks to display the list of available disks.
Choose the disk which you would like to use.
In the Overview page, ensure that DISK STATE is listed as Unattached. If it is not, you might need to either detach the disk from the VM or delete the VM to free up the disk.
In the menu at the top of the page, select Create VM.
On the Basics page for the new VM, enter a Virtual machine name and either select an existing Resource group or create a new one.
For Size, select Change size to access the Size page.
Select a VM size row and then choose Select.
On the Disks page, you may notice that the "OS Disk Type" cannot be changed. This preselected value is configured at the point of Snapshot or VHD creation and will carry over to the new VM. If you need to modify disk type take a new snapshot from an existing VM or disk.
On the Networking page, you can either let the portal create all new resources or you can select an existing Virtual network and Network security group. The portal always creates a new network interface and public IP address for the new VM.
On the Management page, make any changes to the monitoring options.
On the Guest config page, add any extensions as needed.
When you're done, select Review + create.
If the VM configuration passes validation, select Create to start the deployment.
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