If you’re trying to back up your Mac and getting the dreaded “Backup Disk Not Available” message — you’re not alone. Many users report that Time Machine is not working, or backups are stuck on “Preparing backup”, sometimes for hours. Whether your Mac is not backing up at all, or you’re facing an ongoing Time Machine error, the result is the same: your data isn’t protected.
This issue can appear in different forms:
– Time Machine stuck on preparing backup
– Mac backup disk not available
– Apple Time Machine not working with external drive
– Backup failing unexpectedly after update
– Mac backup problem despite having enough disk space
In this guide, we’ll walk you through how to fix these problems step-by-step using a safe Terminal-based method that resets the Time Machine backup process without erasing your data.
Solution
- Open Terminal
Press Command + Space, typeTerminal, and hit Enter. - Copy the command
- Paste into Terminal
In the Terminal window, press Command + V or right-click and choose “Paste.” - Run the command
Press Enter. If prompted, type your admin password.
Note: No characters will appear when you enter the password — that’s normal.
This command safely stops any stuck Time Machine processes and clears system metadata related to backups. It helps macOS re-identify your backup disk and reset the backup queue. Once complete, you’ll notice that:
– “Preparing backup” no longer hangs
– Time Machine detects your disk correctly
– Backups resume automatically
– Errors like “Backup disk not available” or “Mac not backing up” are resolved
Even if you’ve tried restarting or reconnecting your drive with no success, this fix targets the underlying system process that manages Time Machine operations. No files are deleted, and your backup history remains safe.
If Apple Time Machine is not working consistently, this method can be repeated any time the service stalls. Whether you’re backing up to a Time Capsule, external SSD, or network drive, your Mac backup problems should now be resolved.