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Virtual Machine Files and Definitions

Virtual Machine Files and Definitions

As you are likely aware, a virtual machine is made up of a set of files on the storage system. There are a number of different file types that make up a virtual machine, some of which will only be present under certain conditions. Below lists the file types and their functions:

  • VMX – Primary configuration file that stores the virtual machine settings (ie vCPU, Memory, Disks, etc)
  • VMX~ – Change file for original VMX file. Changes are made to the VMX~ first to avoid VMX file corruption (Credit: William Lam)
  • VMX.LCK – Locked VMX file to prevent changes from multiple hosts.
  • VMDK – Virtual machine disk file that stores the contents of the hard drive. Additional drives are appended with a _1, _2, and so on.
  • VMXF – Configuration file for VMs that are in a team (XML file).
  • VMSD – Contains information and metadata regarding snapshots.
  • VMSN – Snapshot state file – stores the running state of the virtual machine when snapshot is taken.
  • <#>.VMDK – Redo-log file created when a VM has at least one snapsho. Stores changes made to a virtual disk while the VM is running.
  • VSWP – Virtual machine swap file created to allow memory over-commitment on a host. Size = Configured Memory Size – Reservation
  • NVRAM – Contains information regarding the BIOS settings for the VM
  • LOG – File to log key VMware activity for troubleshooting purposes
  • HLOG – Log file pertaining to vMotion
  • -AUX.XML – File used to track changes occurring during snapshot activites


 Newly created virtual machine on vSphere 5.5:


Files from a newly created VM


Single snapshot of server shown above:


Files after new Snapshot


Below shows two attached drives, one of which is 40GB thick provisioned and the other is thin provisioned:


Below shows additional files that are created when the VM is powered on, most notably the files surrounding memory functions for the VM:



About The Author

Bryan Krausen

Bryan Krausen is currently working as a Technical Architect with experience in a vast number of platforms.

Bryan has been active within the VMware vExpert community for several years and is the leader of the Louisville VMware User Group (VMUG) and Louisville AWS User Group.

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