“Delta” WIM creation

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JVolkar
Posts: 3
Joined: Mon Apr 10, 2023 11:56 am

“Delta” WIM creation

Post by JVolkar »

I am looking to create a “delta” WIM from two starting WIM files. I see
that —update-of and —delta-from exist and could create a “delta” WIM
*during the capture process*, however my use case is as follows:

1) there is a full disk image for a product; version 1.0 this is used as a
“master1” image for production.

2) version 2.0 of the product is created, and is “master2” for production.

We don’t want to change our normal build and release process.

Starting with master1.WIM and master2.WIM we would like to create a
“delta-1-2.WIM” file where with the master1 and the delta-1-2 files we
could recreate master2. We would like to do this for “patch” distribution
to the field.

Is there a way to accomplish this using the command line today? The two
things we would need are “create-delta”. And “apply-delta” type operations.


Thanks in advance, John

(Sorry admins! I went brain dead and clicked the email icon… Eesh.)
synchronicity
Site Admin
Posts: 472
Joined: Sun Aug 02, 2015 10:31 pm

Re: “Delta” WIM creation

Post by synchronicity »

I'm afraid that's not quite how delta WIMs work. An image in a delta WIM is still logically a full image -- it just refers to file data from other WIM(s). There is no way to capture or apply "just the delta"; you can only capture or apply a full image.
JVolkar
Posts: 3
Joined: Mon Apr 10, 2023 11:56 am

Re: “Delta” WIM creation

Post by JVolkar »

I think I get it now. Hmm. I suppose then that we could modify our capture process to always capture both a full image as well as one (or more) delta(s).

I’d end up with
- master1 (base, no delta)
- master2, and delta1-2
- master3, and delta1-3, delta2-3
- and so on.

And we can change our production process to leave a copy of the originally applied masterN on the unit (actually I think we do this to support a “factory default” feature already).

The number of deltas that we maintain is up to us and is just a time and labor and management problem.

If I understand your reply, there is no way to create a delta other than by doing a capture. And applying the delta requires the master to be present (which we have).

Is there really no method to “combine” two physically separate WIM files into one new file? If there is we could avoid the need to create a million deltas (1-2, 1-3, 2-3, 1-4, 2-4, 3-4, etc).

Thanks for the reply (and I’ll continue to poke around a bit).
synchronicity
Site Admin
Posts: 472
Joined: Sun Aug 02, 2015 10:31 pm

Re: “Delta” WIM creation

Post by synchronicity »

I'm not sure what to recommend exactly, but keep in mind the following:
  • While it's possible to apply image 1 and then image 2 on top of it, the end result is not necessarily the same as applying image 2 alone, since e.g. files that exist only in image 1 are not deleted.
  • A delta WIM can have multiple base WIMs. So, it's possible to have wim1, wim2, and wim3, where wim1 is a "standalone WIM", wim2 is a "delta WIM" that is based on wim1, and wim3 is a "delta WIM" that is based on both wim1 and wim2.
  • wimexport can be used create a standalone WIM from a delta WIM and its base WIMs. So e.g. in the previous example, 'wimexport wim3 1 standalone.wim --ref=wim1 --ref=wim2' would create a standalone WIM containing just the last image.
JVolkar
Posts: 3
Joined: Mon Apr 10, 2023 11:56 am

Re: “Delta” WIM creation

Post by JVolkar »

> A delta WIM can have multiple base WIMs.

I didn’t realize this. So. I could apply delta2-3, and ref delta1-2, and master1. And end up with what essentially was a “master3” being applied… did I get that right?

If so, I think this enough that I can start to test this out without my brain dead fumbling around.

Thanks for the help.
John
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