how to track your clones
Last week I was asked whether I could produce a script that would keep track of Carbon Copy Cloner backup tasks so that a user could tell which of many, multiple backups of the same source disks were the most recent.
Of course, CCC has its own Task History and Disk Center functions to provide information, but these turn out to be insufficient in common scenarios. To see why, let’s consider a hypothetical task set-up and recovery situation.
In this situation, let’s suppose I’m keeping 2-hourly, daily and weekly clones of my mac’s internal disk. While I’m logged in to my mac, I can of course check CCC’s Task History to see when the last back up was, the destination, and whether it was successful or not.
However, suppose the internal disk fails – just the situation for which I keep my CCC backups on a regular schedule. Which disk contains my latest backup? The information from CCC’s history task is on the failed internal disk, so it is not now available to me. Of course, each backup contains CCC’s earlier History too, but there’s several problems here. First, these cloned task histories do not contain the history from the *last* task (that’s only written to the source disk after the last backup completes). Second, to compare them, I’d have to boot each clone individually – a time-consuming and not terribly convenient process. Third, CCC’s ‘Disk Center’ only provides backup information about connected disks if the current startup disk was used to run the backup task. Thus, if I backup Disk B from Disk C, that information won’t be available to me when I startup my mac with Disk A.
Before I discuss the solution to this, let me just complicate the scenario further. I have two other macs – two 13″ MacBook Pros that have been going strong since 2009 – each of which I backup to individual clones. There’s no way for me to see all the backup dates from all my macs with CCC. Further, we don’t need to consider only disk failure as a reason to need comparative backup history. Since some files are shared or swapped across my three macs, there’s no way to find out from CCC’s Task History or Disk Center when the latest backup of any particular one of those files was made, or on which backup disk I can find it. For example, the connected disk ‘MBP Z Clone’ is a scheduled task on my MBP, but looking at this disk when connected to my iMac gives me no information about its backup history:
Fortunately, CCC has two features which make our problems solvable. First, each source disk keeps detailed logs of the backups it has run (from which the Task History and Disk Center info is constructed); secondly, CCC allows us to run a shell script after each task has completed.
These two little features are going to allow us to build a shell script that will write a special log file to the destination after each task completes, and then retrieve it and compare it against both the current source and other disks. That means we’ll be able to get CCC backup data from any disk we connect to any mac, since the data will be stored on the destination disk itself thanks to our shell script (for the technically minded: to avoid permissions problems, the script writes to /Users/Shared/ if it’s a bootable clone, or to the root of a disk that isn’t).
That’s the outline of the problem and the solution. What started out as a simple AppleScripting task soon blossomed into a full-blown app. Although much of the background work I’ve outlined above is achievable via AppleScript, displaying the data effectively is rather cludgy, even if one uses some of the excellent scripting libraries like Shane Stanley’s ‘Myriad Tables’ to improve on the stock AppleScript offerings.
Accordingly, after about a week or so of wrestling with an acceptable solution, I finally came up with the Disk Inspector.app to solve all these problems in one go and add a few niceties on top. 😉
Whatismore, since it’s Christmas :D, I’m publishing this as a free utility on my software site, Sqwarq.com. Check out Disk Inspector’s support and download page here: https://sqwarq.com/disk-inspector
Here’s a quick overview of the main features:
1. See dates of all connected disks that have been backed up via CCC*
2. See the latest backup and (if available) Time Machine backup for the current source disk
3. See the OS Version and Build Number on connected, bootable drives
4. Open any disk’s root folder in the Finder by double-clicking its name in DI’s main view
5. See an estimate of the total and available space on each disk (rounded to the nearest GB)
6. Save all the data to a log file for easy record keeping of your backups
* after completing Disk Inspector’s set up procedure
For full instructions refer to the Support page, but the basic idea is that on first launch, you run the ‘Set Up’ wizard to configure your tasks in Carbon Copy Cloner. Disk Inspector’s ‘Set Up’ wizard walks you through 5 simple steps to accomplish all this.
Once you’ve completed the set up procedure and each of your scheduled CCC tasks has run, you’ll start to see information for each backup disk in Disk Inspector’s main view on any mac (or on the same mac booted from a different drive) that you subsequently connect those disks to.
Disk Inspector runs on 10.10 and higher.
Enjoy, and Happy holidays to all!😀