Time Machine for multiple users

I’ve been using Time Machine on openWRT for some time and it works fine. I wanted to add another Mac, I created new user and everything works fine except Time Machine. New Mac doesn’t work with this because at first that new user wanted to open backup made on another Mac, and said that there is no access to it (I checked logs), and then throws error Signal 11. What’s that? Did anyone manage to make it work?

It will likely depend on how you've "shared" the volume to the macOS devices.

"11" is a pretty critical fault, often due to some unimplemented code path in supporting libraries. If I were to guess, it was a result of the user authorization process.

But it works on another Mac without any problems. I did it in exactly the same way.

@MiL, welcome to the community!

I'm almost certain we're talking about a Mac here.

Then by your own admission, it works.

This is a Mac error, why not call Apple Support?

Created a new user where?

  • on the OpenWrt?
  • on the new Mac?

If on the Mac, why not call Apple Support?


  • Why would it have access to the other backup?
  • Can't you simply use a different path - and not use the same as the other machine?

It is likely permissions-related. macOS uses POSIX-like permissions and metadata. Backup access is controlled and permitted, for example to restore from an older machine to a newer one.

Signal 11 is an error in OpenWRT logs when new Mac wants to connect to Time Machine.

I've got everything configured according to this tutorial:

There is only one path:
path = /mnt/sdb1/Backups

I think that it is a path for every user's backup.

On new Mac I can connect to router by SSH and browse backup folder, but Time Machine doesn't work.

Do I have this right:

  • You set up netatalk on your OpenWRT device as described in the linked guide and have been using the afp share successfully as a network Time Machine backup location for your Mac.
  • You tried to use the same afp share from another mac. It didn't work.

You haven't answered, Lleachii asked where the new user was created, on the new Mac, OpenWRT? Both?

You later clarify that Signal 11 was in the OpenWRT logs. Is that also where you found "that [the] new user wanted to open the backup made on [the] other Mac? "Is that also where you found that access was denied? Or did some of this information come from the Mac's logs or error messages?

If it isn't from the new Mac's, exactly what error messages do you get when you try to set up TimeMachine backups and it fails?

It's strange that any user on a different Mac would try to open the Time Machine backup created on a different machine. Time machine backups are tied to specific machines.

The backup folders are based on the machine name, but they don't rely on the machine name to distinguish them, they use a GUID stored in some of the metadata files (or maybe attributes) in the backup folder. A new machine won't try to backup to a backup folder from another machine on the same network share without explicitly being told to do so. The second mac might try to read the metadata files in the first mac's backup in order to check whether they belong to a different machine, and it will fail if they are owned by a different OpenWRT user. This failure will probably show up in both OpenWRT and Mac logs, but probably won't result in an error shown to the user, because MacOS will likely assume that those files belong to someone else, and that it needs to create a new backup folder.

What OpenWRT user are you connecting to OpenWRT via SSH as? Are you specifying "root?" Is it using the default, which would be the username you used to log into the Mac? Are you specifying the OpenWRT username you recently created?

When you say you can browse the backup folder, do you mean that, after you ssh in, you can use the command line on OpenWRT to ls the shared directory, or that you can also connect to network fileshare from the Finder and browse it using the Finder? If the latter, what username is used when connecting to the network fileshare.

Similarly, what username do you specify when setting Time Machine up to use the OpenWRT hosted network share?

Based on the information we have so far, my guess that either any new OpenWRT user you've created for use with the new Mac hasn't been assigned to the right group, or that the file permissions and/or group ownership weren't set up properly when you first configured netatalk, and its only become a hindrance when adding a new user.


That's correct.

New user in OpenWRT.

Yes, It was in OpenWRT logs. There was also information about accessing backup from another computer, but I think it's not related with this problem. Maybe TimeMachine want's to check all backups it is founding in particular location. When I removed that backup, information about accessing this backup disappeared but Signal 11 still was there.

Nothing, when I pick backup location, it's thinking and a window with location appears again.

Yes, it is user created specifically for that backup. Through SSH it works fine.

The same as I mentioned before.

Everything looks configured correctly, but maybe I overlooked something. I'll let you know if I find anything.