Networked Time Machine backup can't be created in Ventura

I duplicated your problem. I too have an M1 Mac Mini and a MacBook Pro.

It doesn't look like you can backup the M1 Mac Mini 'server' to the external drive you wish to share for networked Time Machine backups. Because Time Machine takes ownership of the external disk and changes it to be a Time Machine drive. When that happens I cannot create folders or files even from the M1 Mac Mini. The Time Machine backups occur at a system level outside of my user account. My M1 Mac Mini local admin user account doesn't have write permissions to the Time Machine drive. Only Time Machine can write to the disk. Therefore the remote users attempting to add the disk for Time Machine will be denied write access. The disk mounts but you can't create a folder or file on it. Therefore Time Machine on the remote Mac will fail.

So the work around would be to turn off Time Machine on the M1 Mac Mini and you can still create the Share and make it a shared Time Machine Destination despite it not actually being a Time Machine drive. For each remote user who backs up with Time Machine you will have the following on the external drive.

Andrew's MacBook Pro.sparsebundle

Jeff's MacBook Pro.sparsebundle

Now if you wish to also backup the M1 Mac Mini to this same disk, then you're going to have to work around the problem a bit. One possible solution is to resize the partition and add a new one. Put the networked user backups on one volume and assign the other volume to the local M1 Mac Mini Time Machine.

Time Machine remote works a bit different than local Time Machine. The remote sparsebundles are disk images that can grow larger over time. There's an option to limit the size when you first start the remote Time Machine connection. Time Machine local takes over the entire disk. Another alternative would be to add another external disk and make that the Time Machine disk for the M1 Mac Mini. A third option would be to create an APFS Volume instead of a partition. This is interesting because both volumes will share the total free disk space dynamically and automatically so you don't need to worry about allocating storage space. This last option seems to be working quite well and would be the recommended way to accomplish your goal. You don't even have to erase the existing disk.

I set the LaCie Time Machine for the local M1 Mac Mini backups and share the LaCie Backup as the Time Machine backup destination. They are both APFS volumes on the same disk and share the free space.

Thanks for the clarification that you have two external drives. One for local M1 Mac Mini Time Machine backups and the second one to be used to simulate a Time Capsule (networked Time Machine).

On the drive intended to be used for others to backup over the network. The problem is if you make that drive a Time Machine on the M1 Mac Mini then it will not work. You merely need to erase that drive and make it APFS. Then go to Sharing and add the drive, right-click the share and check the box for "Share as a Time Machine backup destination". Verify the permissions are correct.

Then from another Mac do not mount the drive. Instead, go to Time Machine and add a new destination and select the drive being shared from the M1 Mac Mini. Authenticate and it should work. Time Machine will mount the drive for you and will do so automatically as needed.

I tried it both ways and found that it doesn't work if you make the drive a Time Machine drive on the M1 Mac Mini. That is because a Time Machine drive is special and it's read only so when the remote Mac tries to backup it will fail because it is read only.

In the scenario where you have only one external drive it is possible to format the drive as APFS and then create a new APFS volume within the APFS Container. It looks like this in Disk Utility:

Then you can make the local Mac use the "LaCie Time Machine" volume and then you add the "LaCie Time Capsule" to be a share. This way you get the best of both worlds on the same drive. APFS volumes within the same Container will share the free space and you don't need to define each volumes size. It will dynamically use the free space automatically.

When looking at the disk "LaCie Time Capsule" you will see multiple files like this:

Andrew's MacBook Pro.sparsebundle

Cindy's MacBook Air.sparsebundle

Tom's iMac.sparsebundle

Two external disks.

1. Is used for the M1 Mac Mini Time Machine and is dedicated to that purpose.
2. Is used to share a virtual Time Capsule backup

The Time Capsule drive should be formatted APFS and it should not be designated as a Time Machine drive. When formatting it APFS do not tell the M1 Mac Mini to make this drive a Time Machine.

In System Settings -> General -> Sharing add the Time Capsule drive and right-click, go to Advanced Options and check the box to Share as a Time Machine backup destination.

The M1 Mac Mini will then advertise the Time Capsule drive as a networked Time Machine. On the other Mac you wish to backup you should be able to select the destination and it should work.

Make sure the Time Capsule drive is directly attached to the M1 Mac Mini, do not use any sort of USB hub, etc. Connect it via a Thunderbolt USB-C to USB-A adapter cable. (or buy a drive that has a USB-C connection such as LaCie, etc.)

I tested this out. The only way it didn't work is if I made the Time Capsule a Time Machine drive. If you do that, the drive is dedicated to the M1 Mac Mini and won't be able to serve the other Macs. When the other Macs backup to the Time Capsule drive, each Mac will create an individual sparse disk image which is formatted APFS internally.

On the Sharing screen, click Options and ensure you have each Mac's user added. SMB users are defined in this screen. These accounts vary from macOS user accounts. They are only for SMB network shares. Also verify the shares permissions are correct.

The example you linked / referenced is using TrueNAS which simulates the environment you have setup with the M1 Mac Mini and the external drive. There are far too many other factors when working with simulated Time Capsules on TrueNAS / FreeNAS, Synology, Linux, etc.

My own personal setup uses a Linux container on LXD on Ubuntu Server to simulate a Time Capsule. It's using Avahi Daemon to advertise the Bonjour mDNS Time Machine over the network. The share is Samba (it too has it's own user accounts for SMB) and the underlying filesystem is ZFS. Not only do I have sparse bundles for each Mac that backs up but they reside on the ZFS filesystem within a ZFS volume. I snapshot that volume every hour and rotate the snapshots. It also sends those snapshots via ZFS Send to another ZFS NAS so I have a replicated copy of the Time Machine sparse bundle.

But I attached a 6TB LaCie external HDD and first duplicated your problem then I was able to get working. The trick was NOT to make that drive a Time Machine drive. You already have a different Time Machine drive for the M1 Mac Mini. The second drive acting as a Time Capsule only needs to be shared and designated as a Time Machine destination in Sharing and you need to define the user accounts via the Options button in the Sharing panel.

ulairi9 wrote:

The other separate, networked drive is a newly formatted APFS drive and it's only set up as a TM Destination. The MacBook Pro recognises this drive on the network but doesn't backup to it, as described above.

Since you have repeated this information a couple of times, it suggests some confusion about how a network Time Machine volume works.

The format for a network Time Machine volume is absolutely irrelevant. It has no meaning in any way. When you back up to a network Time Machine volume, you attach to an SMB network share that fulfils the SMB Time Machine requirements. That link you originally posted describes how to do that on a Mac. But it is very important to remember the difference between the client and the server. Those instructions are for a Time Machine server that just happens to be a Mac. It doesn't have to be. The client machine is completely different.

The server machine could be a Windows server or a Linux server. The file system is also irrelevant. Apple's documentation doesn't do a very good job explaining this. It even says at the bottom, "Time Machine can't back up to a disk formatted for Windows, or to an iPhone, iPad or iPod touch." For networked Time Machine backups, this is 100% false.

It sounds like you are trying to manually login to the server to start the backup. That won't work. You have to do this entirely from Time Machine. In the Time Machine interface, all you do is click "Use Disk". it should display a connection dialog where you can enter your login id and password. You don't have to do anything else. You let Time Machine do all of the connecting and disconnecting for you.

Thank you James for the detailed explanation and instructions. I read through the entire thread, and finally got it to work. And your tip here about restarting File Sharing is crucial!! Share my setup in case other people having the same issue:

TL;DR: Don't share a dedicated TimeMachine drive, it has to be a regular drive; Restart File Sharing after you make the change.

M2 Mac Mini on Ventura 13.4.1(c) connected to one external drive, which I intended to use as both Mac mini local TM backup and share over the network for my other Macs to do TM backup.

• format the external drive as APFS with one Volume I named as "TimeMachine" -- this will be used as Mac mini TM drive
• in disk utility, click Volume (+) to add a APFS volume in the container which i named as "ExternalTimeMachine" -- this will be used for network shared TM drive
• In the Mac mini, set the "TimeMachine" volume as TM drive. System will take over and I no longer have access to it.
• Share the "ExternalTimeMachine" drive as a time machine destination following Apple's instruction
• (THIS IS CRUCIAL) restart File Sharing by turning the toggle off and on.

Voila, now my other mac can use the "ExternalTimeMachine" as the backup drive!

For clarification you cannot share a Time Machine drive. It has to be a regular APFS drive without Time Machine being enabled on it. It's just a simple APFS drive and you share it. In the Sharing settings you right-click to access Advanced Options and then you make it a Time Machine Destination but it is NOT TIME MACHINE.

The Time Machine on the remote Mac controls the backup, it just creates the sparse bundle on the network share for each remote Mac that backs up.

If you are still making the drive you are sharing a Time Machine drive that is a problem.

You already have a Time Machine drive attached to the M1 Mac Mini to backup itself. The second drive formatted with APFS and shared will act like. Time Capsule allowing your other Mac's to backup to this second drive.

In Disk Utility click View -> Show All Devices. The default is to only show the volumes. That will reveal the full tree in the sidebar.

So to confirm, the drive has been formatted APFS and you did not make it a Time Machine drive on the M1 Mac Mini. Then you go to Sharing and add the drive. (you will need to remove the old ones). Then right-click the new Share entry and check the box to make it a Time Machine Destination. Then try adding the Time Machine on the other Mac.

One Tip: After you add the Share, you should turn off File Sharing and turn it back on. I found whenever I changed stuff in sharing it requires File Sharing to be restarted. You can just toggle the ON/OFF button. Turn it off, wait a few seconds and turn it back on. It re-reads the changed share entries and then starts up sharing.

Ventura broke SMB sharing and I don't remember what version finally fixed it. I think it was fixed before your posts in May, but I'm not sure. I think it was .3 or .4 that fixed what they broke.

You could not connect to any share over SMB hosted on Ventura. This only happened for some, and it seemed to be two separate issues which affected different setups. For me, it was tied to custom icons on the Shared drive (it was actually the FinderInfo extended attributes). Removing the custom Icons made it work, again. Others had to wait for the fix.