What is approach for upgrade boot image for e.g I am using default boot images let say BOOTX86 which consists of all network drivers now new requirement few network drivers needs to add.  So need create same replica (copy BOOTX86) package add new drivers distribute into DP. Mention same in task sequence test new boot image? Or add new network drivers into boot image (production) update boot image? My question is if edit existing boot image after that I need to update meaning it will copy or redistribute to all DPs? in case if any issue complete PXE setup will not work due to boot image issue

So how to update boot image safely without production down time?  

If you want to be absolutely sure that it will still work, I personally think, that you should copy the current boot image and create a new one based on that. That will give you the possibility to first deploy the boot image and properly test it before using it for production purposes. It does require good version control to keep track of all the changes and the differences between the boot images.

Thanks please let me know if any option to inject network or drivers to boot image and update to specific DPs  so that based in result it will move to production? As per my understanding refresh, copy boot image package not help full so need to update boot image package once click on update source package or version it will update to all DPs? Please clarify it is possible to inject network or drivers to boot image and update to specific DPs?

No updating it on only specific distribution points is not an option. It would also cause your task sequence to fail in those locations, as it will be looking for the latest version of the boot image.

Thanks so before editing boot image take master copy (boot.wim file) as backup and create new one boot image (replica of master or original) then edit and copy to few DP's and test (make sure that task sequence also selected same) if all works then remove original boot image from all DP's edit same thing redistribute i am right? this method is flexible or safe method?

Peter has the safest option to ensure no down time.

You will to:

• copy your boot.wim
• make your updates 
• import your new boot disk into SCCM (i.e. BOOTX86_v2 )
• make a copy of your production task sequence (i.e. TS_copy)
• assign BOOTX86_v2 as the boot image to TS_copy
• distribute to a distribution point and test using TS_copy
• once you are happy distribute the new boot disk to all distribution points 
• Pilot builds using TS_copy 

Once you do this you can switch to using the new task sequence and boot disk and if something does go wrong you can switch back to the original. Or you can modify the original task sequence to use the new boot disk. Both are quick and easy updates. Once you confirm everything is ok, you can clean up the original boot disk by removing it from the distribution points and deleting it. The same goes for the task sequence that you are not using.