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TNCS-0046 - Catalina Update

October 9, 2019


ChronoSync is ready for macOS Catalina (10.15), but are you ready for Catalina? Apple, with its annual macOS update, has delivered an entirely new file system organization! This affects any backups that access files outside your Home Folder such as Bootable Backups.

This Tech Note explains the changes and offers suggested 'Best Practices' as you make your move to macOS Catalina (10.15).

Before you start, one question. Are you running the latest ChronoSync, v4.9.5? If not, upgrade now! Just click 'ChronoSync->Check for Updates' to make sure you have the latest version.


First and foremost, backup your data before upgrading! This should be standard procedure before any update, let alone a major OS release. Why? Because it is distinctly possible that your updated system will fail to boot, perform poorly or even lose data once the install is applied. Admittedly, this possibility is extremely small - probably well under a 1% chance. But do you really want to take that chance?

Prior to downloading the Catalina installer you should open ChronoSync and manually run all non-bootable backup tasks that you've setup. This ensures that you have redundant backups of your current data. If you have any scheduled tasks, you should then disable the scheduler by choosing "Suspend Scheduler" from the ChronoSync system menu (at the upper right of your menubar).

If you aren't making a bootable backup, stop right now and head over to Standard Bootable Backup. Making a bootable backup is even easier in ChronoSync by using an Assistant! If you want to retain the possibility of reverting to your current macOS after trying out Catalina, you'll need a full Bootable Backup.

When that is all done, run your bootable backup task and test that your backup works. The preferred method is to open System Preferences, choose Startup Disk, and select your bootable backup drive. Restart your system and boot all the way to Finder. If you get this far, all is well. Then open System Preferences -> Startup Disk and re-select your main system drive. Reboot back into it. Disconnect your bootable backup drive and set it aside. Now you're ready for Catalina!


Downloading and installing Catalina is fairly easy and straightforward. You should expect the process to take an hour or so. Some systems will be faster, some will be slower. When finished, you'll boot up your new OS, configure your account and iCloud settings and be on your merry way!

It is typical to see a number of 'Do you want to allow notifications' prompts when you initially log in. Be sure you review and respond to each prompt. We recommend allowing any ChronoSync component to send notifications including ChronoSync, ChronoAgent and ChronoSync Scheduler.

In the vast majority of cases, that's it! You'll be able to use your new OS just as before as if nothing ever happened.


Here are a few things to be aware of:

  1. File System Layout. Catalina utilizes a new APFS file system feature called 'Volume Groups.' The purpose is to designate that two or more volumes are related to each other. Apple uses this feature in Catalina to divide the boot volume into two components: System and Data. The System volume is read-only and contains all the operating system files that should never change during use of the computer. This is a new security feature of Catalina. The Data volume contains everything else, including your home folders. The two volumes are linked together in macOS to appear as one volume to the user. However, there really are two distinct boot volumes mounted, and if you know where to look, they can be found.

  2. Full Disk Access. Catalina continues to, by default, restrict apps from being able to access certain types of data. In order for ChronoSync to be able to access all of your data, you will need to first grant it "Full Disk Access." Our Granting Full Disk Access to ChronoSync tech note outlines the steps you will need to take in order to allow ChronoSync access to all of your data.

  3. "Do you want to allow ChronoSync".... messages. Catalina takes another step forward in restricting Apps from using different features of the system without your permissions. Because of this you may be prompted to allow ChronoSync to access Finder, Post Notifications, and any number of other possible services as you start to initially use ChronoSync. We recommend you accept or say 'Yes' to allow ChronoSync, ChronoSync Scheduler or ChronoAgent Monitor to access the specified service.

  4. Suspended Schedules. If you followed our directions, we told you to suspend your scheduled tasks before upgrading your OS. The reason for this was so your backup tasks won't start firing off after you began using Catalina. You need to take the time to verify that your new operating system is working correctly and that your data is intact before you start running backups. Start with your data files - peruse them in Finder and open a few documents/projects that you regularly use. This will allow you to test your applications, too.

  5. Resume Scheduler. Not just yet! Launch ChronoSync and review each of your Sync Tasks. Open them one at a time and double-check you don't have any 'Cannot Locate Target' messages displayed on the Setup Panel. If so, click 'Choose' and re-select the desired target. Review the 'Readiness' section of the Setup Panel. It is typical to see "This task was configured on a different system." Roll your cursor over the Readiness Warning and use the 'wrench' icon to 'Fix' the warning. Save the Sync Task. Note: Even if you don't change anything, ChronoSync may prompt you to 'Save Changes'. Do so. ChronoSync has made internal changes to the Sync Task to support Catalina. Next, open the Scheduled Task Manager window from the Window menu. Do you have any Bootable Backup scheduled items? If so, disable them temporarily by unchecking the item in the left-side column in the Scheduled Task Manager window. Once that looks good, you can resume your regularly scheduled backup tasks by choosing "Actions->Resume Scheduler" from the ChronoSync menu. (Bootable Backups is a topic in and of itself below!)


You should hold off on resuming bootable backups until you at least have several days of intense Catalina use under your belt. The reason is simple: the bootable backup that you made is your lifeline in case some major problem with the new OS occurs. If you run a bootable backup immediately, you lose that lifeline. Some OS problems may take a while to materialize, so that is why we say you need to use the new OS intensely before you can build confidence in it. Once you are confident you are sticking with Catalina and want to create a Bootable Backup of your new macOS, you have a couple of options on how to proceed.

Option 1: New Bootable Backup

We strongly recommend starting fresh with a new backup volume. There are many reasons, but the primary issue is the new File System Organization utilizing the 'System' and 'Data' Volume Group.

The best method to create a new Bootable Backup Sync Task for Catalina is to use the 'Bootable Backup' setup assistant.

The Setup Assistant will walk you through the process of creating the necessary volume group to support Catalina Bootable Backup. You can either re-use your Mojave bootable backup volume and re-initialize the drive, or start with a new drive for Catalina bootable backups. Remember, if you re-use your Mojave backup volume, you will no longer be able to revert to Mojave.

If you have an existing volume large enough to hold your Mojave backup and you wish to add your Catalina Backup to it, you can use the Setup Assistant to Add the new Volume Group to the existing drive. In the Bootable Backup Setup Assistant, choose your existing APFS bootable backup volume as your destination. In the next step, when asked if you want to erase it, choose instead the option to create a Sibling Volume. This adds an additional volume and configures it appropriately as a Catalina Bootable Backup Volume Group.

Adding the Sibling Volume can be a great approach because you'll have your old bootable backup on one volume and then your new Catalina bootable backup in a volume right next to it. Once you’ve determined your new system and new bootable backup is working properly, you can delete the old bootable backup volume using Disk Utility.

Note: You cannot convert an existing encrypted APFS Volume to an APFS volume group. You'll have to re-initialize the volume to an unencrypted APFS volume.

Option 2: Reuse Existing Bootable Backup

Although we do not recommend using your old/existing Bootable Backup sync task, this may be necessary if you don't have a separate volume to use, you do not have a large enough destination drive to add a Sibling Volume and/or you do not want to erase the existing backup and start from scratch.

You can only use this option if your existing bootable backup volume is unencrypted and using the APFS File System. This won't work on HFS+ backup volumes or encrypted APFS volumes.

Launch ChronoSync and open your existing Bootable Backup Sync Task. Verify the Targets are correct and recognized. Next, take note of the 'Readiness' section of the Setup Panel. ChronoSync will identify the backup volume as not configured for Catalina backup and report "Destination volume is not constructed properly."

Roll your cursor over the Readiness Warning and utilize the 'wrench' icon to "fix" the Readiness Warning. This initiates our built-in tool to convert the destination volume to an APFS Volume Group suitable for Catalina bootable backup.. This will keep your user data intact but the destination won't be bootable until the bootable backup task completes.


Well, that's pretty much it! Always proceed cautiously and think about your actions while performing the update. If something goes wrong, don't panic! If the issue is with the new OS, there are plenty of online communities for you to seek help in. If the problem is with ChronoSync and/or your backup strategy, contact us and we'll be happy to help.


We've covered the basics, above, and the basics are usually good enough for the vast majority of people. However, there’s a few more considerations we'd like to present.

Upgrade on Another Partition. If you have an adequate drive partition available, consider performing the Catalina upgrade on it before doing so on your main drive. The basic procedure would be to perform a bootable backup to this spare partition, boot into it and then install Catalina. This allows you to try out Catalina on a completely separate device. If all goes well and you are happy with it, you can then perform a bootable backup from that secondary device back to your primary drive.

Install Catalina "Clean." If you've been using your Mac for a while, and have undergone several OS upgrades, there’s no doubt that you've collected a fair amount of "cruft" over the years. A clean install is the best way to get rid of that and ensure maximum performance from your computer. You can do this one of two ways. The first is a variation of the above - if you have a spare partition, erase it and run the Catalina installer. You can then tell the installer to install onto the spare partition.

The second way to achieve a clean install is to boot from your bootable backup and then erase your primary system drive. Then when you run the Catalina installer, you should select your newly erased primary drive as your destination. You should probably not use this approach if you do not have redundant backup copies of your data. That's because, for a brief period at least, your bootable backup will be the only copy of your data!

In either case, the new OS will be placed cleanly on the destination device and it will be in as pristine a state as possible. You can use Migration Assistant, as discussed here, to import all your data from your old Bootable Backup.

If your existing backup volume is encrypted APFS and you want to use your existing Bootable Backup Sync Task, you'll have to decrypt the APFS volume before following the steps above. This may take a long time, so starting over from scratch or procuring a new backup drive might be a better choice.

If your existing backup volume is HFS+, you can convert the volume to APFS. Refer to Disk Utility or the command line tool, diskutil to perform the conversion. You can convert without erasing the volume and losing your data.

Note: An external drive may be considerably slower than an internal one. Keep this in mind when making a decision about where to install your OS update.


If you have any concerns or issues related to Catalina, please do not hesitate to contact us.


Oct-07-2019 - Created Internally.