Clone operations and snapshot operations are distinct, each with its own purpose and function calls when using automation tools like PowerCLI or vSphere API.
Clone Operations
Function Call in PowerCLI: To clone a VM in PowerCLI, you would use the New-VM cmdlet with the -Template parameter, specifying the source VM to clone from.
New-VM -Name 'ClonedVM' -VM 'SourceVM' -Datastore 'TargetDatastore' -Location 'TargetResourcePool'
Function Call in vSphere API: In the vSphere API, you would call the CloneVM_Task method on the source VM managed object.
task = source_vm.CloneVM_Task(folder=dest_folder, name='ClonedVM', spec=clone_spec)
Difference Between Cloning and Snapshotting:
- Cloning creates a separate, independent copy of a virtual machine. The new VM has its own set of files on the datastore and a unique identity within the vCenter environment.
- Cloning is often used for deploying new VMs from a template or existing VM without affecting the original.
Snapshot Operations
Function Call in PowerCLI: To create a snapshot of a VM in PowerCLI, you would use the New-Snapshot cmdlet.
New-Snapshot -VM 'SourceVM' -Name 'SnapshotName' -Description 'SnapshotDescription'
Function Call in vSphere API: In the vSphere API, you would call the CreateSnapshot_Task method on the VM managed object.
task = vm.CreateSnapshot_Task(name='SnapshotName', description='SnapshotDescription', memory=False, quiesce=False)
Difference Between Cloning and Snapshotting:
- A snapshot captures the state and data of a VM at a specific point in time. This includes the VM’s power state (on or off), the contents of the VM’s memory (if the snapshot includes the VM’s memory), and the current state of all the VM’s virtual disks.
- Snapshots are used for point-in-time recovery, allowing you to revert to the exact state captured by the snapshot. They are not full copies and rely on the original disk files.
Examples
Cloning a VM:
- You have a VM called “WebServerTemplate” configured with your standard web server settings.
- You clone “WebServerTemplate” to create a new VM called “WebServer01”.
- “WebServer01” is now a separate VM with its settings identical to “WebServerTemplate” at the clone time but operates independently going forward.
Creating a Snapshot of a VM:
- You have a VM called “DatabaseServer” that is running a critical database.
- Before applying updates to the database software, you take a snapshot called “PreUpdateSnapshot”.
- After the snapshot, you proceed with the updates.
- If the updates cause issues, you can revert to the “PreUpdateSnapshot” to return the VM to the exact state it was in before the updates.
When performing snapshot and clone operations in a VMware environment, different files are created and used for each process. Here’s a breakdown of the file types associated with each operation:
Snapshot Operation Files:
When you take a snapshot of a VMware virtual machine, the following files are associated with the snapshot operation:
- Snapshot Descriptor Files (
.vmsd and .vmsn):
.vmsd – This file contains the metadata about the snapshot and child snapshot information.
.vmsn – This file stores the state of the VM at the time the snapshot was taken. If the snapshot includes the memory, this file will also contain the VM’s memory contents.
- Snapshot Data Files (Delta disks,
.vmdk):
- Delta
.vmdk – These are the differential files that store changes made to the VM disk after the snapshot was taken. They are often referred to as “delta disks” or “child disks.”
Example:
VM_Name-000001.vmdk – A delta disk created after the first snapshot.
VM_Name-000001-delta.vmdk – The differential file that stores the disk changes since the snapshot.
- Snapshot Configuration Files (
.vmx and .vmxf):
- These files are not created new for the snapshot; instead, they are updated to reference the current snapshot.
Clone Operation Files:
When you clone a VMware virtual machine, a new set of files is created for the clone, similar to the original VM’s files:
- Virtual Disk Files (
.vmdk and -flat.vmdk):
.vmdk – The descriptor file for the virtual disk, which points to the actual data file.
-flat.vmdk – The data file that contains the cloned VM’s virtual disk data.
- VM Configuration File (
.vmx):
.vmx – This is the primary configuration file that stores settings for the cloned VM.
- VM Team File (
.vmxf):
.vmxf – An additional configuration file used if the VM is part of a team in VMware Workstation.
- BIOS Boot File (
.nvram):
.nvram or .nvram– This file contains the BIOS state of the VM.
- Log Files (
.log):
.log – These files contain log information about the VM’s operation and are created for the clone.
Example:
- If you clone a VM named “ProdServer” to a VM named “TestServer”, you will get a new set of files like
TestServer.vmdk, TestServer.vmx, TestServer.vmxf, and TestServer.nvram, among others.
In both operations, the directory structure on the datastore would also include a VM folder named after the VM (for clones) or the snapshot (as a subfolder for snapshots). The exact naming conventions for the files may vary depending on the version of the VMware product and the specific operations performed.
Keep in mind that during a cloning operation, if you opt to customize the clone (e.g., changing the network settings, hostname, etc.), you may also have a customization specification file (.vmtx) associated with the clone. This file stores the customization settings applied during the cloning process.
Moreover, during a clone operation, if you choose to clone from a snapshot point rather than the current state, the clone will be an exact copy of the VM at the point when the snapshot was taken, including the VM’s disk state as captured in the snapshot’s delta disk files.
Below you will find PowerShell examples using VMware PowerCLI to clone a virtual machine and to create a snapshot of a virtual machine. Before you can use these cmdlets, you need to install VMware PowerCLI and connect to your vCenter Server or ESXi host.
Cloning a Virtual Machine
To clone an existing VM to a new VM, you would use the New-VM cmdlet in PowerCLI. Here’s an example:
# Connect to vCenter
Connect-VIServer -Server 'vcenter_server_name' -User 'username' -Password 'password'
# Clone VM
$sourceVM = Get-VM -Name 'SourceVMName'
$targetDatastore = Get-Datastore -Name 'TargetDatastoreName'
$targetVMHost = Get-VMHost -Name 'ESXiHostName'
$location = Get-Folder -Name 'TargetLocationFolder' # The folder where the new VM will be located
New-VM -Name 'NewClonedVMName' -VM $sourceVM -Datastore $targetDatastore -VMHost $targetVMHost -Location $location
# Disconnect from vCenter
Disconnect-VIServer -Server 'vcenter_server_name' -Confirm:$false
Make sure to replace 'vcenter_server_name', 'username', 'password', 'SourceVMName', 'TargetDatastoreName', 'ESXiHostName', 'TargetLocationFolder', and 'NewClonedVMName' with your actual environment details.
Creating a Snapshot of a Virtual Machine
To create a snapshot of a VM, you would use the New-Snapshot cmdlet. Here’s an example:
# Connect to vCenter
Connect-VIServer -Server 'vcenter_server_name' -User 'username' -Password 'password'
# Create a snapshot
$vm = Get-VM -Name 'VMName'
$snapshotName = 'MySnapshotName'
$snapshotDescription = 'Snapshot before update'
New-Snapshot -VM $vm -Name $snapshotName -Description $snapshotDescription
# Disconnect from vCenter
Disconnect-VIServer -Server 'vcenter_server_name' -Confirm:$false
Replace 'vcenter_server_name', 'username', 'password', 'VMName', 'MySnapshotName', and 'Snapshot before update' with your details.
These examples assume you have the necessary permissions to perform these operations. Always test scripts in a non-production environment before running them in production.