Install error -69854

Ran into the same error today, no chance to recover, am restoring from time machine backup now 😬 Frustrating to see such errors in such a late beta. My config: iMac 5K late 2014, 1TB Fusion Drive

I have the same situation

how to build it ?

Did anyone ever respond to this with guidance? I tried updating Mojave this morning and received the same - com.apple.DiskManagement error -69854 - Error message. Trying to figure out if this is salvagable?

>tried updating Mojave this morning

As macOS 10.14 Mojave is now public, user-centric (non-beta*) queries/comments such as this are perhaps best put to AppleCare's public community support forums, Apple's twitter support account and/or Apple’s YouTube Support Channel vs. risking off-topic here in the DevForums, thanks and good luck.

https://support.apple.com/

Same here. What van I do? Big pannic.

Same here. After this error, the Mac was stuck in an endless "There was a problem, need to restart" loop without ever really booting up.

The following helped me:

1. Force shut the Mac down.
2. Upon startup, keep Cmd + Alt + R pressed, before the Apple logo comes. If it comes, you were too late.
3. You will enter the Internet recovery mode. Here, you can reinstall the MacOS your device initially shiped with. I did not lose any data this way.
4. Now you can upgrade back to High Sierra: https://support.apple.com/en-us/macos/high-sierra

I do not know yet how to upgrade to Mojave, these are the instructions I can give to help you recover what's possible in case you are stuck in the same place I was.

Same problem here. iMac 27”. About 40 minutes in went to the “can’t install” I did do as instructed and restarted doing diagnostics but passed with flying colors, so there’s something new in beta 2 that iMac doesn’t like. The problem is now I’m stuck on beta 1. Ugh? How do we force install beta 2?

Same issue in here (no Beta), but no chance to reinstall MacOS, only choice to reinstal with Mojave which landed to the same results, same error. Any other advice, suggestion without a time machine backup?

Fixed with Shift+Alt+Command+R shortcut during restart and then with "internet recovery" - original OS reinstalation (Sierra). No data lost. iMac connected to the internet with cable. With Cmd+Alt+R only Mojave was an option with same failure again.