Custom Open Virtual Format (OVF)

Question

As everyone knows OVF is Open Virtual Format for exporting virtual appliances it is helps in many aspects and reliable. I got to know about OVF from wiki Open Virtualization Format. Hypervisors like VMware bare-metal hypervisor, Virtualbox, Hyprer-V, has provided their tools for converting VM to OVF/OVA formats. Got to know from below helpful links VMware, Hyper-v,VirtualBox.

But how can i do the custom OVF if i have only VHD,VHDX,VDI,VMDK files of some Virtual Machine? Does there any difference between VMDK and VMDK from exported OVF? Is there any programmatic approach by using which i can do this easily?

Thanks

Answer 1

VMware OVF package consist of sparse disk. I did it simple way with the help of VirtualBox, VirtualBox provides you command line option for disk conversion so you can get your disk in target format and then create package, Package consist of .OVF file and .MF file along with disks in one folder.

.MF File consist of SHA1 check-sum of all files in package

.OVF consist of deployment configuration i.e Controller, Disks, RAM, CPU etc.

No need to study everything just export some VM in OVF format and then refer that .OVF and do changes as you want and update check-sum in .MF file

Answer 2

how can i do the custom OVF?

VMWare OVF file is just an .xml file. It contains the information about resources like disk file .vmdk, cd/disk file .iso, memory, vCPU, Network Adapter, virtual disk size and host configuration parameters.

For reference you can export ovf file from any VM which is already created/running on host.

Does there any difference between VMDK and VMDK from exported OVF?

We can export VMDK from host not from OVF(.ovf is just file). I think exported VMDK and VMDK are same. Because from exported VMDK can also be used to bring-up VM on host.

Is there any programmatic approach by using which i can do this easily?

You can update the ovf file using any programming language. But I prefer to choose python and library.

I prefer to use .OVA instead of .OVF file. Basically .OVA is tar of .VMDK, .OVF, .MF(cryptography file of all files in .OVA tar (optional)), .iso(optional), etc.

IF you use .OVF file to bring-up instances, you need to keep all the information provided files in same directory like .VMDK, .iso, etc. There may be chances of missing files or placed in different directory.