Time Machine - Read Only

[iMacBooked]

Hi everyone,

I understand that since the latest OS, a Time Machine external HDD is always 'Read-Only' and that it is normal considering the way the OS handles backups.

However, I would like this Time Machine drive to be shared with my other Macs (so that they can store their back-ups on it as well).

As soon as I take the necessary steps (enabling sharing of the drive), the other Macs do see the drive as a Backup option, but every time they try to connect to the drive, they fail saying that they have no permissions to connect to the drive. I'm guessing this has to do with the fact that a Time Machine backup drive is now 'Read-Only'.

Is there any solution for this?

Thanks in advance.

 

[Fishrrman]

I've never used time machine and I'm not familiar as to whether or not there's anything peculiar about drives that are tm drives.

However...

I'll offer this as something to try (with no promises):
Take the tm drive to one of your OTHER Macs.
Let the drive icon mount on the desktop when you connect it.
DO NOT "open" the icon.
Instead, click on it ONE time to select it.
Bring up the "get info" box for the drive icon (command-i).
At the bottom, click the lock and enter the password (for the Mac you're using).
Now, put a checkmark into "ignore ownership on this volume" (sharing and permissions).
Close get info.

Does this make a difference as to whether or not you can access the drive?
(again, no promises)

 

[Brian33]

However, I would like this Time Machine drive to be shared with my other Macs (so that they can store their back-ups on it as well).

As soon as I take the necessary steps (enabling sharing of the drive), the other Macs do see the drive as a Backup option, but every time they try to connect to the drive, they fail saying that they have no permissions to connect to the drive. I'm guessing this has to do with the fact that a Time Machine backup drive is now 'Read-Only'.

Is there any solution for this?

Yes, I think so...

If your TM volume is read-only I think that implies that you have it formatted as APFS (which is now the default for new TM volumes).

APFS has containers, which can contain one or more volumes. I think what you want to do is create new volumes for the other Macs, within the same APFS container. This is quite easy to do with Disk Utility (although I'm unable to test that this works for TM containers in particular, I think it does).

1. Open Disk Utility.
2. Use the View menu to Show all Devices.
3. In the left pane, select the Container line that is just above your TM volume.
4. In the right-hand pane, click the "+" button at the top to create a new volume.
5. Give it a sensible name, then optionally use the Size Options to make sure this volume always has at least xxGB (Reserve Size) or to make sure this volume never grows larger than xxGB (Quota Size) (see below).
6. Once you Add it, you'll notice on the left pane that there are two volumes within the same Container.

Now try setting up TM on another Mac to point to the new volume.

One thing to remember is that all volumes within a container share the same space. You might need to read up on how that works. Then you might want to set a Reserve and/or Quota size for each of the volumes. If you don't, I'd expect as your TM backups for your multiple Macs grow and get thinned, the actual amount of data in each volume could change over time. I don't know if that could cause a problem for TM or not. If you set Reserve & Quotas for each Mac's volume, it would be more predictable and act similarly to having separate fixed partitions, and perhaps be less likely to confuse TM.

 

[gilby101]

I'm guessing this has to do with the fact that a Time Machine backup drive is now 'Read-Only'.

Strictly the volume is not 'read-only'. Rather it is protected so that only local TM can write to it. But solution as @Brian33 says.