How do I back up two different MacBooks on one external drive?

I have two MacBooks and one 2TB MyBook Essential.

One machine is running ElCapitan and the other runs Catalina.

The files on both machines are completely different as, of course, are the operating systems. I need to keep both back ups completely separate.

The MyBook is not permanently connected to either machine. This is for a one-off ‘point in time’ back up.

I have already created a Time Machine backup for the ElCapitan machine. I now need to create a separate Time Machine backup for the new Catalina machine.

Can anyone offer guidance as to what steps to take? I’m keen to avoid any conflict between the two backups.


simple… buy another hard drive so you have one for each MacBook

2TB drives aren’t that expensive, so it’s an easy solution.

Well…yes…but…is that really necessary if I’ve plenty of space on the existing drive?

If backing up two laptops to one drive is impossible then that’s what I’d do. But surely it’s possible?

you’ll eventually run out of space one day, … and 2TB is not really a ‘lot of space’ these days.

If the Software supports it,maybe … if it doesn’t then, No.

Backup Software asks for a “Target” where to backup …and that is in most cases the Root of the Entire Disk and not a specific place / folder or partition on the hard drive.

It should not conflict at all. The only pain is disconnect and reconnect to different computer. JoeySmyth is right on gettting another drive. Or you could get a WD NAS single drive.


For the record, I took the plunge, connected the drive and…a cinch. An additional folder is automatically created and both back ups sit as distinct entities.

I’m guessing that both your MacBooks are less than 1TB. What method did you use in the end by the way - just plug them in and start Time Machine on each MacBook in turn?

If I were to do that myself, I would have partitioned the drive into two volumes using Disk Utility then given each volume distinct names like El Capitan and Catalina. Then I would just open each MacBook in turn and point its version of Time Machine at the appropriately named volume.

Still, if your way works then sobeit. :wink: