How to clone a running virtual machine in vSphere

• First you have to login to service console using a ssh client like putty. You can also do the same on a ESXi server if you have enabled the Remote Tech Support Mode.
• Then you have to take a snapshot of the running virtual machine using vi client.
• After that you have to create a new virtual machine using the vi client.
• From the service console delete the virtual hard disk of the newly created virtual machine:

# cd /vmfs/volumes/datastore1/newvm
# rm *.vmdk

• Then copy the virtual hard disk from the original virtual machine to the new virtual machine:

# vmkfstools -i /vmfs/volumes/datastore1/oldvm/oldvm.vmdk /vmfs/volumes/datastore1/newvm/newvm.vmdk

• If you want to create a thin virtual hard disk use this syntax:

# vmkfstools -i /vmfs/volumes/datastore1/oldvm/oldvm.vmdk -d thin /vmfs/volumes/datastore1/newvm/newvm.vmdk

• Delete the snapshot from the running original virtual machine using vi client.

For more info read this post.

Accessing the virtual machine's console directly from the command line

Please read the following article from VMware.

Determining if a virtual machine is Fault Tolerant capable outside of vCenter Server

Please read this article from VMware

Renaming a virtual machine and its files

Please read this article from VMware