The Time Machine service in Mountain Lion Server hasn’t changed much from the service in Lion Server. To enable the Time Machine service, open the Server app, click on Time Machine in the SERVICES sidebar. If the service hasn’t been enabled to date, the ON/OFF switch will be in the OFF position and no “Backup destination” will be shown in the Settings pane.

Click on the ON button to see a list of volumes to use as a destination for Time Machine backups. This should be large enough to have space for all of the users that can potentially use the Time Machine service hosted on the server. When you click the ON button, a list of volumes appears.

Here, click on the volume to save your backups to. In this case, it’s the internal hard drive; however, in most cases the Backup destination will be a mass storage device and not the boot volume of the computer. Once selected, click “Use for Backup” and the service will start. Don’t touch anything until the service starts. Once started, change the backup destination at any time using the Edit button.

Time Machine Server works via Bonjour. Open the Time Machine System Preference pane and then click on the Select Backup Disk button from a client to see the server in the list of available targets, much as you would do with an Apple Time Capsule.

Under the hood, a backup share is creating in the file sharing service. To see the attributes of this share, use the serveradmin command followed by the settings option and then the sharing:sharePointList:_array_id:/Shared Items/Backups

sudo serveradmin settings sharing:sharePointList:_array_id:/Shared Items/Backups

The output indicates the options configured for the share, including how locking is handled, guest access disabled, generated identifiers and the protocols the backups share listens as:

sharing:sharePointList:_array_id:/Shared Items/Backups:dsAttrTypeStandard\:GeneratedUID = "1B1C7CFB-2B95-4087-B28B-C786E9CD68E2"
sharing:sharePointList:_array_id:/Shared Items/Backups:smbName = "Backups"
sharing:sharePointList:_array_id:/Shared Items/Backups:afpIsGuestAccessEnabled = no
sharing:sharePointList:_array_id:/Shared Items/Backups:smbDirectoryMask = "0755"
sharing:sharePointList:_array_id:/Shared Items/Backups:afpName = "Backups"
sharing:sharePointList:_array_id:/Shared Items/Backups:smbCreateMask = "0644"
sharing:sharePointList:_array_id:/Shared Items/Backups:nfsExportRecord = _empty_array
sharing:sharePointList:_array_id:/Shared Items/Backups:path = "/Shared Items/Backups"
sharing:sharePointList:_array_id:/Shared Items/Backups:smbUseStrictLocking = yes
sharing:sharePointList:_array_id:/Shared Items/Backups:smbIsGuestAccessEnabled = no
sharing:sharePointList:_array_id:/Shared Items/Backups:name = "Backups"
sharing:sharePointList:_array_id:/Shared Items/Backups:smbInheritPermissions = yes
sharing:sharePointList:_array_id:/Shared Items/Backups:ftpName = "Backups"
sharing:sharePointList:_array_id:/Shared Items/Backups:smbIsShared = no
sharing:sharePointList:_array_id:/Shared Items/Backups:afpIsShared = yes
sharing:sharePointList:_array_id:/Shared Items/Backups:timeMachineBackupUUID = "29B22ADA-97A3-46B2-9CB3-8EF9AFC9334E"
sharing:sharePointList:_array_id:/Shared Items/Backups:isTimeMachineBackup = yes
sharing:sharePointList:_array_id:/Shared Items/Backups:smbUseOplocks = yes
sharing:sharePointList:_array_id:/Shared Items/Backups:dsAttrTypeNative\:sharepoint_group_id = "59161FF9-78E7-4A41-B071-B6E60866694F"
sharing:sharePointList:_array_id:/Shared Items/Backups:isIndexingEnabled = yes
sharing:sharePointList:_array_id:/Shared Items/Backups:mountedOnPath = "/"

Once the service is running, administrators frequently fill up the target volume. To move data to another location, first stop the service and then move the folder (e.g. using mv). Once moved, use the serveradmin command to send settings to the new backup path. For example, to change the target to /Volumes/bighonkindisk, use the following command:

sudo serveradmin settings sharing:sharePointList:_array_id:/Shared Items/Backups:path = "/Volumes/bighonkindisk"

Another way to see the share and attributes of the share is through the sharing command:

sharing -l

Which should show output similar to the following:

List of Share Points
name: Backups
path: /Shared Items/Backups
afp: {
name: Backups
shared: 1
guest access: 0
inherit perms: 0
}
ftp: {
name: Backups
shared: 0
guest access: 0
}
smb: {
name: Backups
shared: 0
guest access: 0
}

There’s also a Bonjour service published that announces to other clients on the same subnet that the server can be used as a backup destination (the same technology used in a Time Capsule).

One major difference between the Time Machine service and others is that there’s no specific serveradmin option for tm or tmutil (the Time Machine command line) or timemachine. Instead, most everything piggy-backs off the sharing service. Also, what I consider a major difference is that most other services now have generic names (e.g. Address Book is now called Contacts, iCal is now called Calendar, etc). The only services still using marketing terms as their names are really Profile Manager, Time Machine and Open Directory. I would expect these to eventually be called Profiles, Backup and Directory to keep the naming convention already started with the rest of the services.

I think that as a free aspect of OS X Server Time Machine Server is well worth the money for small workgroups. However, there are backup solutions from 3rd party vendors worth far more than their purchase price due to reduced disk capacity requirements (e.g. through deduplication), reduced overhead (e.g. by streamlining or accelerating traffic for the backup protocols, or even offloading all the work to the client systems) and allowing for more redundancy to backups (e.g. 2 targets). This additional logic can at first appear to come at a steep cost, but when you look at bandwidth, disk and other expenditures to get Time Machine server integrated it can be a challenge. Also, Time Machine is built to work via Bonjour, meaning that by virtue it’s then limited to smaller subnets. Time Machine Server is a great add-on, but many organizations may quickly outgrow it. Not all though, and so for a SoHo comprehensive server that needs to provide for client-based backups, OS X Server has a great feature in Time Machine.

While I found plenty to ramble on about in this article, nothing has really changed since the Lion iteration of the service. Mass deployment is still the same, as is client side configuration. One change is that the screen for the Time Machine Options on the client no longer has an option for managing Versions, as seen below.