Mac: Backup with Time Machine to a NAS - how it works

For a backup of your Mac on a NAS, OS X comes with the Time Machine program. If your NAS supports Time Machine, you can easily create backups on your network drive. We'll show you what you have to do.

Step 1: Set up a user account for Time Machine on the NAS

It is worthwhile to set up an extra user account for Time Machine. Then you can use the Time Machine on the NAS with several Macs and regulate the size of the storage space used:

1. Log in to the user interface of your NAS as an administrator. If you've never done this before, the article "Set Up NAS Server" gives you a few tips.
2. Now create your own user account for Time Machine. With Synology, for example, you can do this in the "Control Panel - User" menu. Enter a useful username (e.g. TimeMachine) and set a password. The account does not have to have admin rights, membership in the "Users" group is sufficient.
3. Later you can set a "quota" for a user account. This is the maximum amount of data that the user can save on the NAS. You should choose a quota for the Time Machine account that is larger than your system hard drive - preferably twice as large. This gives you enough space to hold more than one backup.
4. Also give the Time Machine user account permission to access the services of your NAS. Check the box next to FTP, File Station, Network Backup or similar. The user account setup is now complete.

Step 2: Create a Time Machine folder on the NAS

Now you need another folder in which Time Machine can put the backups:

1. Now go to the area on your NAS where the folders and storage space are managed. Find a "volume" there, ie a drive on which there is enough space for your backups. If you have set up a quota, it must apply to the named drive.
2. Now create a new folder on this volume and also name it "Time Machine".
3. Assign the appropriate rights for this folder in the sharing or access settings. Only the user "Time Machine" should have read and write access to the folder called Time Machine. You should better remove the ticks from all other user accounts (including the admin). So nothing gets mixed up.
4. The last but most important point: set up file services for Mac on your NAS, sometimes called "AFP". Search for the corresponding settings on your NAS and switch on the "Time Machine" service in the options. If your NAS does not have this option, follow the instructions in the next paragraph. Otherwise, the NAS is now set up.

Special case: NAS without time machine support

If your NAS does not have any settings for the AFP and Time Machine, you have to help a little. Get Mac OS X to accept officially unsupported drives for Time Machine. Your NAS is tuned to a backup solution with an economy bundle:

1. Open a terminal in the program folder. Enter the following command there (without quotes): "defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1". Time Machine now shows other network drives.
2. Now open the hard disk utility. You have to create a so-called sparsebundle image, which you then copy to your NAS drive for Time Machine. You can find picture instructions in the gallery.
3. Go to "New Image" in the hard disk utility. There you create a growing bundle image in any folder on your Mac. Name the image "Time Machine" and set the size to 100 MB. The format must be "Mac OS Extended (Jounaled)", a simple Apple partition is sufficient.
4. After clicking on OK, the program creates your image in the named folder and mounts it. It now appears on the left in the hard disk utility. To copy it, you have to unmount it: Right-click on the image and select "Eject image".
5. Now navigate to the network drive on your NAS that you created for your time machine backups. Log in there with the Time Machine user account and copy the Sparsebundle image you just created to the network drive. Don't worry about the size: the image grows with you until it reaches the set quota.

Step 3: Turn on the Time Machine on Mac

Now you are almost there: Just tell your Time Machine where to save the backups:

1. Make sure you are connected to your Time Machine folder on the NAS. If not, go to the menu "Go - Connect to server" in the Finder. Enter the IP of the NAS and the time machine folder - for example "afp: //192.168.20.5/Time Machine".
2. Now open the system settings and there the Time Machine. Go to the "Select volume" button and click on your time machine network drive. Confirm with "Use backup hard disk".
3. You can now make special settings under Options - e.g. if a folder is not to be backed up.
4. Now switch the Time Machine on the left to "On" and the backup process can begin. From now on, Time Machine always backs up comfortably to your NAS.

If you don't have a NAS, but you have a FritzBox: In another practical tip, read how to use your FritzBox as a NAS.

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If the NAS doesn't have time machine support, just trick the time machine. With the command "defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1", Time Machine also displays all other drives that are eligible for a backup.

Go to the hard disk utility and create a growing savings bundle image under "New Image" on your hard disk.

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If successful, the image appears in the column on the left. Eject it with a right click and "Eject Image".

Now make sure that you are connected to your new time machine drive (in the Finder "Go - Connect to server"). Log in there with the new Time Machine account and copy the new Sparsebundle image from your hard drive to the network drive.

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Now you can call up the time machine options in the system settings and enter your new network drive under "Select volume". You are already done with that.