Time Machine: Multiple Macs, multiple shared folders?

Discuss backup and restore functions of the DiskStation with respect to computer clients, such as Synology Data Replicator, Time Machine, or other client backup software.
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bjamieson177
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Time Machine: Multiple Macs, multiple shared folders?

Unread post by bjamieson177 » Sat Feb 17, 2018 3:35 am

Hello! I've recently purchased a DS918+ and I'm setting it up to be a Time Machine backup server for four Macs. I've found a lot of great information right here on this forum, but I had an idea for a setup and was wondering if this sounds like a good idea.

I was setting up a single shared folder, with quota enabled (4TB), which each Mac connects to and dumps its Time Machine backup. To login, each Mac has its own Time Machine user on DS, which is separate from a normal user, and only has privilages to use that shared Time Machine folder. Each Time Machine user also has a quota of 1TB.

I discovered, however, that while each Mac is logged into the DS to do its backup, it can't login with its normal user credentials to do anything else.

Instead of having multiple Time Machine exclusive users with a single shared folder, I was thinking of having multiple shared folders, one for each Mac, with 1TB quota each, assigned to each normal user. That way a backup could be running while the user could also do their normal business on DS.

Not the most tidy, having all of these shared folders flying around, but I think it would prove to be less annoying overall.

Anyone else think this is a good idea? Thanks!

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Rusty1281
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Re: Time Machine: Multiple Macs, multiple shared folders?

Unread post by Rusty1281 » Sat Feb 17, 2018 6:27 am

Why can’t you login with user accounts while using time machine accounts? Any error?

I use it like this all the time for years and there were no problems.
Synology DS918+ (4x4TB WD RED - RAID 5 with 2x250GB 960EVO NVMe) | Synology DS412+ (4x3TB WD RED - RAID 5) | RT1900AC

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Re: Time Machine: Multiple Macs, multiple shared folders?

Unread post by bjamieson177 » Sat Feb 17, 2018 3:15 pm

I was skeptical at first, since through FInder I could not easily specify which network share got which user login. I assumed that I would have to mount the shared folder in Finder before Time Machine would see it, preventing backups from occurring until that would happen. But I see that when I open Time Machine prefs and click "Add or Remove Backup Disk..." I have the opportunity to use the Time Machine User's login credentials, which appear to connect independently from how I would normally mount a shared folder.

Glad I was wrong! Thanks.

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Re: Time Machine: Multiple Macs, multiple shared folders?

Unread post by adambier1 » Mon Mar 12, 2018 5:48 am

Rusty, I've followed your directions in various threads and have gotten multiple computers backing up to a single Time Machine directory (using their own accounts and quotas and assigning permissions via a new TM_computers group). Once the different computers start backing up (creating their own sparsebundle subdirectories), each user has read and write access to the other users' subdirectories. This is something of a security problem. I've tried to make inherited permissions explicit and then deleting the TM_computers group's access permissions from each sparsbundle directory (hoping that the owner account would still have full permissions), but that broke access from my Mac. I then tried to re-add read and write access for just that account, but to no avail--even then, Time Machine from that Mac is broken.

Is there any way to have a shared folder configured for Time Machine access by multiple computers using multiple accounts without each account having full access to the other accounts' sparesbundles?

Thanks much,
Adam

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Re: Time Machine: Multiple Macs, multiple shared folders?

Unread post by Rusty1281 » Mon Mar 12, 2018 1:27 pm

Hi Adam,

can't say I have tried killing the permissions on a single shared folder just because I didn't needed it. All my users are in a 'users' group so considering that you have made a custom group there might be an issues with it. On the other hand if this turns out to be 2 much of a problem maybe you could just add more shared folder (one for each TM users) and set it up that way. Each account to a specific TM shared folder. Move sparse bundles from your single shared folders to those new created ones and the TM on your macs should continue to work as they should.

Adding a minimum of read permissions on the root folder for TMs for your TM_computers and then adding r/w permissions on the sparse files inside it should make it work so that each user can work with its own image. On top of this if you wanna block access to each others users read permission for any other TM backup but their own, I think you will have to add deny permission on those sparese files as well to counter balance the main TM root read permission of your TM_computers group. Have you tried that?
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Re: Time Machine: Multiple Macs, multiple shared folders?

Unread post by adambier1 » Mon Mar 12, 2018 7:33 pm

Hi Rusty,

Thanks very much.

I've kept everything in one shared folder (less confusing UI for individual users), but have removed the TM group and just left every user as a "user."

What seemed to solve things was to make sure to add read/write access to the overall Time Machine folder and the applicable sparse bundle subfolder for each TM user BEFORE deleting TM group R/W access (which had been inherited by the user)--even a brief period of the user account not having proper access seemed to cause the breakage.

Going forward, I won't rely on permissions inherited from the TM group (which is now gone), nor those inherited from the overall Time Machine folder, so after creating a new user and adding R/W permissions for the overall Time Machine shared folder, I'll go to the properties for the applicable sparse bundle subfolder, make inherited permissions explicit, and delete the other TM users, leaving the owner-user (and admins) with full access rights (and will tick the box to make the change recursive). That way, the user's access to their own sparse bundle is never interrupted.

Thanks again,
Adam

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