MacOS – Time Machine stopped working after upgrading to Yosemite

I had to reformat the external drive I use for Time Machine. It said there was a permissions problem, that it was Read Only - which it wasn't, and a look at the Info for it confirmed it was Read & Write. Still, I just erased the drive and started again. Works fine now.

My take from this Apple Discussion thread is that the solution causes Time Machine to create a full new backup rather than adding to the other backups, but previous backups will be kept (not sure of actual behavior). Anyway, here is the posted solution (edited formatting and grammar for readability):

By default, the WD Sharespace creates a hidden share called WD_Backup and a user called wd_backup with a default password of backup.

Using the example in the blog:

sudo tmutil setdestination afp://user:pass@host/share

and assuming the following: (all default settings with the exception of the WD Sharespace Server Name)

Server Name: TimeMachine

Volume Name: DataVolume

User: wd_backup

Password: backup

You should execute the following in Terminal:

sudo tmutil setdestination afp://wd_backup:backup@TimeMachine/WD_Backup

In addition, you can validate that you are using the correct User and Password details by:

• Launching the Finder and clicking on 'Go' from the menu

• Clicking on 'Connect to Server...'

• Entering: "afp://TimeMachine/WD_Backup" in the Server Address field and clicking 'Connect'

  You'll be prompted to enter the Username and Password to the share; the default username and password are stated above.

If your machine cannot resolve the Time Machine Server Name, then replace "TimeMachine" with the IP address of your WD Sharespace server; this will mount a drive to the WD_Backup folder, underwhich you will find the .sparsefile that Time Machine uses to store your backup. All this is covered in the WD Sharespace User Guide on page 46 under the Time Machine configuration section.

Note that the original poster also wrote:

However, if entering afp://wd_backup:backup@192.168.1.150/WD_Backup instead of afp://192.168.1.150/WD_Backup it gets to mount it from the Finder window (Command+K). I have tried this while writing this post, because as you were so sure that it worked (even though for me the "straightforward" solution does not work) I decided to try this last thing! Right now it is backing up everyting, so thank you very much for all your help!

Good luck!