Some backup volumes don't appear in the Finder sidebar

If you created a bootable copy of Catalina or Big Sur in the past, and then proceed with CCC backups to that volume on Monterey without specifically using the Legacy Bootable Backup Assistant, CCC will remove the incompatible System volume from the destination. The remaining Data volume appears just fine on the Finder Desktop, and also in the volume list when you select "Computer" from the Finder's Go menu. The Finder sidebar, however, will not show these volumes, regardless of your Finder preferences to show external volumes in the sidebar, and regardless of any attempts to drag the volume explicitly into the sidebar.

We have reported this issue to Apple (FB9739492) and we are currently awaiting a response.

Workaround: Choose "Computer" from the Finder's Go menu to see your destination volume in the Finder.

Apple's SMB filesystem client causes system stalls, random application crashes, and may lead to kernel panics

We have received several reports (primarily from Apple Silicon Mac users) of unruly macOS behavior that occurs while copying files to an SMB-mounted NAS volume. The behavior includes the following:

  • Random application crashes
  • Prompts to grant various macOS system services access to the login keychain (i.e. because the service that retains the unlocked keychain reference crashed, thus locking the keychain)
  • Laggy mouse behavior
  • System stalls that eventually end with a reboot and kernel panic report

Workaround: Users that reported similar trouble on macOS Big Sur reported that using AFP rather than SMB consistently resolved these behaviors (in cases where using AFP is an option):

  1. Eject the NAS volume if it's currently mounted
  2. Open CCC and select the applicable backup task
  3. Click on the Source or Destination selector (whichever is applicable for your particular task)
  4. Hold down the Option key and choose "Switch to AFP" (provide the credentials for the NAS volume again if prompted)
  5. Save and run the task

[Potential] Workaround: Slow down CCC's file copier to reduce "kernel_task" CPU usage

We do not yet have confirmation that this works, but we suspect that high CPU usage by the macOS system service that implements the SMB filesystem client could be causing this trouble. To slow down CCC's file copier:

  1. Open CCC and select the applicable backup task
  2. Click the Advanced Settings button at the bottom of the window
  3. Select the "Performance & Analysis" tab
  4. Drag the "File copier CPU priority" slider to the left, to the "lowest" setting
  5. Click the Done, button, then run the task again

CCC will not update the System volume on a Legacy bootable backup (Big Sur and later)

Starting in macOS Big Sur, the system now resides on a cryptographically sealed "Signed System Volume". That volume can only be copied using Apple's proprietary APFS replication utility ("ASR"). Right now, ASR will only copy whole volume groups (System and Data); we can't choose to copy just the System volume. As a result, every time an OS update is applied to the source, you would have to erase the whole destination volume (including any existing snapshots on that volume) just to update the system on the destination. We made a feature request to Apple in September 2019 (FB7328230) to allow ASR to clone just the System volume. We do not anticipate that Apple will implement our requested functionality.

To avoid deleting your snapshots and the rest of your backup, CCC will not update the System volume on the destination when System updates are applied to the source.

Our recommendation: We recommend erasing the destination only for the purpose of establishing the initial bootable backup. CCC can then use its own file copier to maintain the backup of your user data, applications, and system settings.

Workaround: Any time you want to make the OS on the destination identical to the source, simply click on the Destination selector and choose Legacy Bootable Backup Assistant... to configure CCC to re-erase and reclone the entire volume.

Finder will not show, nor allow you to set custom icons on other Catalina, Big Sur or Monterey startup volumes

Finder will show and allow you to customize the volume icon for your current startup disk, but not for other Catalina+ startup volumes that your Mac is not currently booted from. This problem is not specific to CCC backups, but we see this frequently because CCC can create copies of macOS System volumes. This problem is the result of a design flaw in the implementation of custom icons in an APFS volume group. Up to macOS Catalina, the custom volume icon is stored in a file at the root of the startup disk named ".VolumeIcon.icns". To keep the System volume read-only, yet allow the apparent modification of this icon file, Apple chose to create a symbolic link at the root of the startup disk that points to System/Volumes/Data/.VolumeIcon.icns. For the current startup disk, this path resolves correctly because the Data member of the volume group is mounted at /System/Volumes/Data. That's not the case for external volumes, those Data volumes are mounted at /Volumes/CCC Backup - Data (for example). As a result, the symbolic link to .VolumeIcon.icns is unresolvable for any volume that is not the current startup disk.

We reported this issue to Apple in May 2020 (FB7697349) and we are still awaiting a response.

Alternative: We recommend creating "Standard" backups instead of creating a legacy bootable backup. Finder will issue no challenges to customizing the icon of a volume with a Standard Backup.

Other Catalina+ startup disks can't be renamed in the Finder

Finder will let you rename the current startup disk, but you won't be able to rename any other startup disks that have an installation of Catalina, Big Sur or Monterey because the System volume is mounted read-only.

We reported this issue to Apple in November 2020 (FB8912480) and we are still awaiting a response.

Solution: Unmount and remount the volume in Disk Utility, then right-click on the volume in Disk Utility's sidebar and choose the option to rename the volume.