How do I revert to a previous OS version without losing data after updating to OS27.2?

Reverting to an older major version of macOS is not simple. You need to boot into Recovery OS, erase your internal drive, then install the older macOS, then restore from a backup made prior to the recently applied upgrade. Even then, the firmware on the Mac may have been updated, meaning potential conflicts and a possible need for DFU mode and a Configurator revive/restore, which would need to be done via another Mac connected to yours. If that sounds complicated and risky, then you're assessing the situation correctly. Also note that in no case can you install a version of macOS that is earlier than the version installed on your Mac when it came out of the box. 

Sounds like that is unnecessary. If Intel apps were running on macOS 26 Tahoe, they should run on macOS 27 Golden Gate (but they will not run on macOS 28, in the fall of 2027).

Rosetta 2 (the macOS engine for running Intel apps on Apple Silicon) is needed for Intel apps. Even if it was installed on your Mac previously, the upgrade to macOS 27 Golden Gate removed it for some users (me, included). Upgrades to macOS 27.2 (from Tahoe or before) reportedly no longer remove Rosetta 2 if it was previously installed. If Rosetta 2 is not installed and you launch an Intel app, you’ll be prompted to install it. That is what happened here, when I launched an app that I had used frequently on Tahoe then launched for the first time after upgrading to Golden Gate.

If that prompt does not appear, it may help to install Rosetta 2 using Terminal. Apple provides instructions for that HERE. The short version is launch the Terminal app (find in Spotlight or in Applications > Utilities) and paste the following, then press return.

softwareupdate --install-rosetta

A warning is triggered when you launch an Intel-only app, and you will see it every time you launch such an app. Launching a recently used Intel app again won't trigger it, but if enough time has passed then you'll see the warning again for that app. For example, I last used the SynologyAssistant app to check on my NAS over a month ago, and launching it generated the banner message.

To avoid this issue you need to run only Universal or Apple Silicon apps. For apps that are Intel only, contact the developers and push them to release updated versions of their apps (but keep in mind that they have over a year before their apps stop working on macOS). 

To see which of your apps are Intel and thus need to be updated or they won't run on macOS 28 (Fall 2027), hold the Option key and click the Apple menu, then select System Information (the top item). Select Applications in the Software section of the sidebar, then click on the Kind column header to sort them. 

Some apps aren't readily identifiable by the name, but when you select that app you will get more info. For example, 'commandFilter' is a component of the Epson printer drivers. If you no longer use them, then apps like that can be safely deleted. The location to the application/extension can be seen in the report, to navigate to the app in Finder simply select and copy the above path up to and including the last / (but not the app name itself) then in Finder select Go menu > Go to Folder, paste the path and press return. As an example, the path to be pasted from the example above is: 

/Library/Printers/EPSON/Fax/Filter/

Here's what Apple has to say about updating your apps:

Learn how to update Intel-based apps for Apple silicon - Apple Support

Without Rosetta 2 installed, the first Intel application that you launch should throw a dialog offering to install Rosetta 2 for you.

Otherwise, see https://osxdaily.com/2020/12/04/how-install-rosetta-2-apple-silicon-mac/

You lose Rosetta 2 support in macOS 28 (Fall 2027), so pre-planning for that loss of Intel app support should not resort to procrastination about that functionality replacement.

You may just need to re-install rosetta. I recall reading the it was inadvertently disabled by the update.

I'd take that route before going through the nightmare of attempting to downgrade.

I am a little confused by the question because the heading and the explanation in the body seem to be addressing two slightly different issues.

If your immediate concern is that several applications have stopped working after updating to OS 27.2, the first step should be to establish why they have stopped working, rather than immediately looking at reverting to an earlier OS version.

Apple's announcement regarding Intel application support in OS 28 is about future compatibility. It doesn't necessarily mean that every Intel application is guaranteed to work under OS 27.2, or that any problems you're experiencing are necessarily related to the same issue.

There is also an important distinction between an Intel-based Mac and an Apple silicon Mac running Intel applications through Rosetta. The distinction matters because the implications of Apple's announcement are different for each.

If your intention is simply to get your existing applications working again, reverting the OS may be one option, but it isn't necessarily the first or best solution. Downgrading can also involve erasing the startup disk, so a full backup is essential before attempting it.

Perhaps you could clarify whether you're asking how to downgrade safely, or whether you're primarily trying to understand why your applications have stopped working after installing OS 27.2?

Those are two different questions, and the answer depends on which problem you're actually trying to resolve.

michaelfromdub wrote:

I just updated to OS27.2 and now several of my intel based apps are no longer working. ... Some of the programs are old and no updates are available or I would have to spend a lot of money to upgrade.

As a general statement, Intel apps should continue to run in macOS 27 (Golden Gate) under Rosetta 2.

However, you DID say "Some of the programs are old and no updates are available " which may be an indication that they are too old & out of date to work with Golden Gate.

• What version of macOS were they previously running in / what version did you upgrade from?
• How about if you identify the apps; perhaps users here can suggest fixes or workarounds.

michaelfromdub wrote:

They all worked perfectly on version 26.8. I have reinstalled Rosetta2 again but still no luck.

Then maybe you should clarify what you mean when you say they don't work...

Exactly what is happening?

michaelfromdub wrote:

Did that still not working

FotoStation Not Working After Updating to macOS 27.2 – Troubleshooting

First of all, the error report provides a useful clue as to why FotoStation has stopped working following the update from macOS 26.8 to 27.2.

1. What appears to be the problem?

The key error in the crash report is:

Library not loaded: /usr/lib/libiodbc.2.dylib

FotoStation is an older Intel-based application that relies on this supporting system library to run.

When it tries to launch, macOS cannot find the library in the location where FotoStation expects it, so the application closes immediately.

This does not necessarily mean FotoStation itself is damaged.

2. Is this a Rosetta 2 problem?

Not necessarily.

Rosetta 2 allows older Intel applications to run on Apple Silicon Macs by translating their instructions. However, it cannot replace missing system components that an application depends on.

An application can therefore still be compatible with Rosetta 2 but fail to launch because a supporting library has been removed, relocated or changed in a newer macOS release.

This could explain why FotoStation worked perfectly under macOS 26.8 but stopped working after upgrading to 27.2.

Reinstalling Rosetta 2 and FotoStation has not helped because the missing component may be part of macOS rather than the application itself.

3. Recommended next steps

First: Contact FotoWare, the developers of FotoStation, and ask whether they have a compatibility fix for macOS 27.2.

Website:

https://www.fotoware.com/platform/products/fotostation/downloads

Specifically mention the missing libiodbc.2.dylib library and ask whether they can provide a solution for older versions of FotoStation.

Second: Check which version of FotoStation you are running. This will help establish whether a known compatibility issue or workaround exists.

Third: Establish exactly which Mac and processor you have (Intel or Apple Silicon, such as M1, M2, M3 or M4), as this may affect the available solutions.

4. Can the problem be fixed without replacing FotoStation?

Possibly. The missing iODBC library may be obtainable separately, but simply downloading it and placing it on the Mac is not necessarily sufficient. FotoStation must be able to locate and load it correctly.

Any workaround should be approached carefully, rather than changing protected macOS system files or security settings.

Conclusion

At this stage, the evidence points towards a compatibility issue between FotoStation and macOS 27.2, rather than a problem with Rosetta 2 or a damaged FotoStation installation.

The priority should be to establish whether FotoWare can provide a fix or whether a safe workaround is available.

Hopefully, this can be resolved without having to replace perfectly usable software or lose access to years of photographs and cataloguing work.

Re-install the app.

Sorry but refer to a later posting in this thread

FotoStation Not Working After Updating to macOS 27.2 – Troubleshooting