need a clone a Linux VM and change hostname, IP,SM,GW looking for automation. Please suggest.
Have you looked at New-OSCustomizationSPec and New-OSCustomizationNicMapping?
Dimitar did a series of post on how to use them.
See Working with Customization Specifications in PowerCLI Part 1, Part 2 and Part 3
If some settings can't be done this way, you can always fall back on the Invoke-VMScript cmdlet (but note that it requires the VMware Tools).
Blog: lucd.info Twitter: @LucD22 Co-author PowerCLI Reference