Separate Time Machine backups from a single HD

Discussion in 'OS X El Capitan (10.11)' started by 31rhcp, Aug 22, 2016.

  1. 31rhcp macrumors member

    May 18, 2010
    I currently have an external HD with two computers' Time Machine backups (so there are two folders inside the Backups.backupdb folder with TM backups). I would like to separate these so that they each have their own HD.

    I tried copying one of the folders contains one machine worth of TM backups to a new drive, but when I plugged it in and tried a backup, it ignored the copied backups and started a new Backups.backupdb folder. It seems that I can't move any files/folders in or out of a Backups.backupdb folder.

    Is it possible to get around this? What I planned on doing was copying both backups over and deleting one once the copy was complete to separate them (though it would be much easier if I could copy them individually). However, I can't seem to even delete these files.

    Can this be done?
  2. KALLT macrumors 601

    Sep 23, 2008
    Honestly, it is best to start with a new backup and either remove the old data relating to the device or keep it for a while. Manual copying of Time Machine data is painful and prone to problems. If you want to do this, then you have to copy the entire backupd directory to the target volume. Before you do that, you have to make sure that your destination volume has ‘ownership’ enabled. You can do that by right-clicking on the volume in Finder and selecting Get Info. There should be checkbox at the bottom which must be unchecked (click the lock to change it). It is easier if you can restore the entire volume to the partition with Disk Utility. Once both partitions are ready, you need to disassociate the backup of one device in System Preferences and target the other volume instead. There might be some additional configuration necessary.

    If the backups are working, then you can proceed with deleting the old backups. You cannot do this with Finder or regular Terminal utilities. Apple provides a tool for this. You have to open a Terminal window and enter the following command, but you have to be careful! The command takes a path and deletes that path and its backups for you, safely. You have to be very specific and point exactly to the directory, otherwise it may delete from another node.
    sudo tmutil delete /Volumes/your_time_machine/Backups.backupd/your_device

    This will delete all backups of the device on that volume. You can get that exact path by typing the following command on the device you want to remove:
    tmutil machinedirectory

    If there are spaces in your path, then you have to escape them with a backslash like this: Time\ Machine, or you have to put the entire path in quotes: "/Volumes/Time Machine/Backups.backupd/MacBook". If you do not do this, you might end up falling back to another node and cause tmutil te remove too much.
  3. 31rhcp, Aug 22, 2016
    Last edited: Aug 22, 2016

    31rhcp thread starter macrumors member

    May 18, 2010
    I understand the painful part since it is a long process. What exactly do you mean by prone to problems? I have done this a few times (but I always copied the entire Backups.backupdb folder in the past) using two drives and eventually they stop being able to back up properly. This has been happening before any manual copying though.

    Thanks! This is great and is what I was looking for. I'll give this a shot in a day or two when I have time for the big transfer. Thankfully, I will have two identical drives before I do any deleting so even if I do mess up the path I will have a backup backup.
  4. KALLT macrumors 601

    Sep 23, 2008
    Finder doesn’t handle hard links very well and this can create some weird problems. There is also the risk of permission problems and failure to ‘inherit’ the backup. You can of course do this, but it takes time. Just make sure that your backups are actually working before you attempt the removal. :)
  5. 31rhcp thread starter macrumors member

    May 18, 2010
    Of course, :). I'm not overly bothered by the time though it is a little annoying.

Share This Page