External HDD mounting

Hardware
1

I use a 2018 Mac Mini and I have three external HDD via a dock attached to it. One is Time Machine, one Carbon Copy Cloner and finally a third which contains important files (copies of documents, photos etc). My problem is that when I boot the computer it tries to load them and doesn’t boot until they are unattached. It boots fine when they are unplugged. All the “Googling” I have done tells me how to mount a drive, not how to get my computer to ignore them on booting. Any suggestions please? Thanks

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I keep two drives attached to my Mac Mini (1 data, 1 TM) and haven’t seen this problem. Sounds like something (program, etc) may be keeping a file, etc. open on one of your drives.

Does it reboot normally when you type the following into terminal: sudo shutdown -r now

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If you are comfortable with terminal you
can do something like this.

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I tried that a little while ago, but it no longer seems to work in the latest version(s?) of macOS.

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…hmm, it worked last time I used it (Sierra?)

However, I have since password protected the
drives, and upon boot get prompted for password.

If I don’t enter a password, they don’t mount

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However I think @WayneG might be on to something.

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https://discussions.apple.com/docs/DOC-7942

Alternatively, you might find Disk Arbiter can do this for you.

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And here is the last line in the KB article from @bowline

“ Note: If all of your disks are encrypted, there is an easier method. For any disk that you don’t want to automatically mount, simply don’t save the password to the keychain.”

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Thanks all. I’ll have a go at your suggestions.

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My problem is that when I boot the computer it tries to load them and doesn’t boot until they are unattached. It boots fine when they are unplugged.

That’s weird… is the carbon copy a fully bootable drive? It may be that the Mac isn’t sure which one it should boot from. Try with that one unplugged maybe, and if it’s resolved

Either way, I’d reset PRAM and SMC, then make sure in System Preferences, the correct startup disk is selected.

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Thanks all for your comments. I still don’t know why the mac tried to boot to an external HDD. I managed to trace it to a back up disc using Chrono Sync. I’ve now attached it to my Synology NAS and backed up that way, so I’ve got round it. Thanks.

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