HELP! Unintended OS installer at startup

[wannabeafrog]

Hello,

Today I woke up to this annoying "macOS couldn't be installed on your computer" issue on startup. Following some instructions that I found online, I managed to use my computer regularly using the startup manager and picking my regular startup disk. However, by doing this, I also found the first choice of my computer boot disk is a "MacOS installer" that I have no idea where it comes from, and this seems to be causing the whole problem. Anyhow, in order to work, now I must ALWAYS turn on my computer and run startup manager, otherwise I keep getting the error message; this is rather annoying and worrisome.

For the record, I did check out if I had any pending or wrongly installed updates in the app store, but only a couple third party apps have pending updates and they shouldn't be related to the system startup at all.

It may also worth mentioning that when I first turned my computer ON today, I had plugged an external HD that actually has another OS in it (Its an old HD with some files I need and didn't get to back up properly), but I never had this issue before.

I would like to get rid of this "MacOS installer" disk and get my computer back to normal. Any help is greatly appreciated!

 

[treekram]

Does the "MacOS Installer" appear on the left side of the Finder? If so, right-click on it, select "Get Info". If you have a disk image that's auto-mounting, look for the "Disk image" attribute. That should say where the disk image file is. If it is a disk image, you can try to delete the file after you eject it.

If "MacOS Installer" is not showing up as a disk image and you don't have external disks connected to your computer, post the information that "Get Info" is showing.

You can change the startup disk by following the instructions in the following:
https://support.apple.com/en-us/HT202796

After you select your correct startup disk, make sure the text "You have select macOS, ???? on the disk macOS" appears below the selection of disks. After that, see if you can restart correctly. Even if you can delete the disk image file, you should go through this process to make sure your "macOS" disk is the one that will boot. (Otherwise, the system may be confused at the next start and take a little time to figure out the old "macOS Installer" no longer exists.)