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upgrading to catalina from mojave using an external drive/disk

K

kalamama

macrumors newbie
Original poster
Apr 17, 2020
5
0
Hi there

Have been using an external hard drive to boot my Mac since about 2 years ago when the internal disk became corrupted/damaged.

Currently on Mojave and trying to update to Catalina. Downloaded the update and when prompted to restart I get the "no entry" logo. I then reboot and hold the option key to boot up using "my passport for mac" however that only reboots using Mojave rather than Catalina, any advice?!
 
Its a Mac Desktop! When I downloaded the 8gb upgrade I did select the external drive for it to be loaded onto...
 
It looks like your Mac uses a standard sata drive.

Have you considered replacing the internal drive with a solid state drive?

The internal drive isn't seen at all in disk utility?
 
How do I go about doing a clean install? Will I lose all my data on the external drive? I wouldn't have a clue how to replace the internal drive with a ssd! Have just checked disk utility and can confirm the internal drive is showing and is SATA...
 
kalamama said:
How do I go about doing a clean install? Will I lose all my data on the external drive? I wouldn't have a clue how to replace the internal drive with a ssd! Have just checked disk utility and can confirm the internal drive is showing and is SATA...
Click to expand...
If it sees the internal drive, use disk utility to check the disk.

Since the internal drive hasn't been used for a while, you can use disk utility to erase and do a clean install of Catalina to see if you can get the internal to work. If you can, create a time machine or CCC backup of Mojave and use the back to restore data to Catalina.
 
Tried First Aid and it failed and said to back up (which I already did a few years back onto the external drive), since then everything is saved onto the new drive. So I'll try erasing it? How do I then go about doing a clean install and time machine/ccc backup?
 
CCC is carbon copy cloner. I have not used it before, I have only used time machine.

Regardless of which program you use, you need to have another external drive on which to create the backup.

You can erase the internal drive without creating a backup because all you want to do it see off you can install an os to the internal. I recommended not having your Mojave external connected while using disk utility. You don't want to erase Mojave by accident.
 
kalamama said:
Tried First Aid and it failed and said to back up (which I already did a few years back onto the external drive), since then everything is saved onto the new drive. So I'll try erasing it? How do I then go about doing a clean install and time machine/ccc backup?
Click to expand...
Before you erase and reinstall your OS, first disconnect your external hard drive.

After that is done, turn on your Mac while holding Cmd - R.

Then choose Disk Utility, Erase Drive, and be sure to select "Show all Devices." Erase the drive at the very top (i.e. the main drive).

After you have erased the drive, hit quit on disk utility which should take you back to the main MacOS recovery screen.

Finally select reinstall MacOS and follow the steps to do that and you'll be good to go!

Just be sure you have any backups you need. If all your data is on your external drive though, you won't need to worry about backups unless you for any reason erase that drive.
 
I've had no problems installing Catalina to external drives.
Both to SSDs and platter-based hard drives.

BUT... OP...
My advice is that unless you have a compelling reason as to why you need Catalina...
...don't do it.
Stick with Mojave.
MUCH better version of the OS...
 
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