File Permissions Issue

[ITZCode]

I am having an issue accessing a specific file on my unRAID box. It's a Time Machine backup and is in the .sparsebundle format. I have tried changing the permissions under the user share and that hasn't fixed it. I'm thinking that OSX may have changed the individual file permissions. Any help would be appreciated!

 

Thanks!

[John_M]

It isn't a file. It's a folder structure containing many, many small files, known as "bands". And, yes, OS X sets the permissions and if you try to "fix them" yourself you'll completely mess them up. It works like this:

 

To use Time Machine on a NAS effectively you need to set up a user and password on the NAS. When you select the NAS share as the backup destination in Time Machine preferences you are asked for a username and password - you need to supply the ones you set up on the NAS. They are remembered in your keychain so that you don't have to keep entering them each hour when Time Machine performs its backup. Within the designated share a sparse bundle is created and formatted as an HFS+ disk image, with the name that you're prompted to enter when you set the destination. A typical name is Time Machine Backups. That disk image is mounted by OS X every time Time Machine runs but it remains invisible (usually!). The mounted disk image is written to in the same way and with the same file structure as a physical disk that's set as a Time Machine destination. So it has a Backups.backupdb folder in its root, which contains a folder named for your Macintosh computer, which in turn contains the dated and timed folders containing the backups. These uppermost folders are owned from an OS X perspective by root:staff, with the folders representing the backed up hard disks owned by root:wheel. Within the backups themselves ownerships are exactly the same as for the files they are backing up.

 

The band files within the sparse bundle are owned by the user who has read/write permission that you set up before creating the backup destination.

 

This applies whether the NAS is an unRAID server or any other server that supports the AFP protocol. The easiest option may be to start afresh.

 

[John_M]

Here's a link to a very useful guide to Time Machine: http://pondini.org/TM/Home.html

 

[ITZCode]

Thanks, I'll try that!

[ITZCode]

Would there be any way to recover the data stored in that share?

[John_M]

If you can get OS X to mount the sparse bundle disk image you can open it in Finder and drag files out of it. To do that you need to mount the unRAID share on your Mac, then double click the .sparsebundle folder. Whether you can do that will depend on what exactly you have done to the permissions.