Stop-sign appears when tryin to connect to external harddrive

aguenther

macrumors newbie
Original poster
Mar 6, 2019
8
0
Frankfurt, Germany
Hello,

my 1GB external hard drive can suddenly no longer boot from my MacBook Pro (2016). The prohibition sign appears, although the access rights of the hard disk are okay.
Strangely enough, it works fine from my old MacBook Pro (2009) El Capitan. Can someone help me? I would be very grateful for that.

Greetings
 

Longkeg

macrumors 6502
Jul 18, 2014
294
107
S. Florida
Troubleshooting job 1: Is it the computer or is it the drive? Or is it some weird combination of the two?

Does it only happen with that particular drive or is it happening with any external drive you try to connect? Could someone have been playing around with the MBP’s Security/Privacy preferences in System Preferences?
 

CoastalOR

macrumors 68020
Jan 19, 2015
2,455
899
Oregon, USA
Have you used Disk Utility to run First Aid to check the external drive?
Do you have a backup of the external boot drive?

You might also consider reinstalling El Capitan on the external using Recovery (CMD + r on startup) Reinstall OS selection.
 

Fishrrman

macrumors P6
Feb 20, 2009
17,179
5,536
Are you trying to BOOT FROM the external drive?
If so, does it have El Capitan (10.11.x) on it?

According to everymac.com, a 2016 MacBook Pro requires 10.12.1 (Sierra) to boot.
If that's the case, an external drive with El Cap on it CANNOT BOOT a 2016 MBP.
 
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aguenther

macrumors newbie
Original poster
Mar 6, 2019
8
0
Frankfurt, Germany
Troubleshooting job 1: Is it the computer or is it the drive? Or is it some weird combination of the two?

Does it only happen with that particular drive or is it happening with any external drive you try to connect? Could someone have been playing around with the MBP’s Security/Privacy preferences in System Preferences?
Unfortunately I only have this one. Nobody than myself has excess to my MacBook.
[doublepost=1561128614][/doublepost]
Are you trying to BOOT FROM the external drive?
If so, does it have El Capitan (10.11.x) on it?

According to everymac.com, a 2016 MacBook Pro requires 10.12.1 (Sierra) to boot.
If that's the case, an external drive with El Cap on it CANNOT BOOT a 2016 MBP.
Hi,
both are on Mojave latest version.
[doublepost=1561128873][/doublepost]
Troubleshooting job 1: Is it the computer or is it the drive? Or is it some weird combination of the two?

Does it only happen with that particular drive or is it happening with any external drive you try to connect? Could someone have been playing around with the MBP’s Security/Privacy preferences in System Preferences?
Hi,
Yes, I used First Aid successfully. I have only this hard drive.
[doublepost=1561129332][/doublepost]
Have you used Disk Utility to run First Aid to check the external drive?
Do you have a backup of the external boot drive?

You might also consider reinstalling El Capitan on the external using Recovery (CMD + r on startup) Reinstall OS selection.
Hi again,
could you tell me, how I can reinstall Moc OSX on the hard drive, when I am unable to start from this volume...÷
 
Last edited:

CoastalOR

macrumors 68020
Jan 19, 2015
2,455
899
Oregon, USA
Hi again,
could you tell me, how I can reinstall Moc OSX on the hard drive, when I am unable to start from this volume...÷
Didn't you say you could boot from "Strangely enough, it works fine from my old MacBook Pro (2009) El Capitan" in your first post? Use the old MBP and select to reinstall El Capitan to the external drive.
 

aguenther

macrumors newbie
Original poster
Mar 6, 2019
8
0
Frankfurt, Germany
Hi,
you are right. I forgot. When I boot from the old MBP will ist be possible to reinstall Mojave on the hard drive? Or will it be restricted to a resinstall of El Capitan, which wont't help, because I wanted to save my Mojave installation. Am I wrong.
Best regards
[doublepost=1561138028][/doublepost]
How the heck are you booting from a 1GB drive?
What operating system can be installed on 1GB?
Sorry, it is 1TB
 

CoastalOR

macrumors 68020
Jan 19, 2015
2,455
899
Oregon, USA
Hi,
you are right. I forgot. When I boot from the old MBP will ist be possible to reinstall Mojave on the hard drive? Or will it be restricted to a resinstall of El Capitan, which wont't help, because I wanted to save my Mojave installation. Am I wrong.
Best regards
Follow my instructions in post #3. Boot into Recovery on the old MBP (running El Capitan), then select Reinstall which will be El Capitan since you will be booted from the El Capitan Recovery.

BTW, you did not answer my questions in Post #3. If you have errors from the drive then that will need to be addressed before a OS reinstall which may require erasing the drive which is why asked if you have a backup. It is also advisable to have a backup before a OS install.
 

aguenther

macrumors newbie
Original poster
Mar 6, 2019
8
0
Frankfurt, Germany
Follow my instructions in post #3. Boot into Recovery on the old MBP (running El Capitan), then select Reinstall which will be El Capitan since you will be booted from the El Capitan Recovery.

BTW, you did not answer my questions in Post #3. If you have errors from the drive then that will need to be addressed before a OS reinstall which may require erasing the drive which is why asked if you have a backup. It is also advisable to have a backup before a OS install.
I don't have a backup and I don't understood how this proceedure could solve my problem. Because what I need is a working backup of my mojave installation. Following your instruction , as I understand, will result in a working backup of my old El Capitan installation on my old MBP¿ Or do I get anything wrong¿ I am German and could't find help in the German Mac forums, therefor I sought help in this forum. Probably my English is not good enough to get anything right.
Regards
 

CoastalOR

macrumors 68020
Jan 19, 2015
2,455
899
Oregon, USA
I don't have a backup and I don't understood how this proceedure could solve my problem. Because what I need is a working backup of my mojave installation. Following your instruction , as I understand, will result in a working backup of my old El Capitan installation on my old MBP¿ Or do I get anything wrong¿ I am German and could't find help in the German Mac forums, therefor I sought help in this forum. Probably my English is not good enough to get anything right.
Regards
I didn't know you were talking about Mojave. Your first post said nothing about Mojave, only El Capitan. Mojave makes sense. I was wondering about El Capitan since the lowest OS for the 2016 was Sierra, but then the 1 GB drive in the first post did not make sense also.

EDIT: Wait a minute, hold everything. Mojave does not support a 2009 MBP, so how does booting from your external drive with Mojave work?

EDIT 2: I went back and reread your 1st post. I thought you meant you booted from the external with the external drive, but in fact you said "works fine" with the 2009 MBP. Could you please clarify what that means? Does your 2016 MBP have a bootable OS on the internal drive?
 
Last edited:

aguenther

macrumors newbie
Original poster
Mar 6, 2019
8
0
Frankfurt, Germany
Yes, there is a bootable OS on the drive, but I can't open it. Stop sign. Thank you very much for your patience and sorry for all the missing information.
Regards
 

CoastalOR

macrumors 68020
Jan 19, 2015
2,455
899
Oregon, USA
Yes, there is a bootable OS on the drive, but I can't open it. Stop sign. Thank you very much for your patience and sorry for all the missing information.
Regards
Let me confirm that I understand. Your internal drive on the 2016 MBP does not have a working macOS installed and the external 1 TB boot drive with Mojave will not boot. You have no backup.

If I'm right, then it seems you are out of resources and need to make an appointment with the Apple Store in Frankfurt to get their assistance in diagnosis and getting a working OS installed.