How to Verify Time Machine Backups
This verification offers a simple way to know if the Time Machine backup data stored on an server or Time Capsule has been modified or corrupted, and can be a helpful troubleshooting trick for some situations.
How to Verify Time Machine Backups on Mac OS
- Be sure the Time Machine backup volume is connected to the Mac as usual (network or otherwise)
- Pull down the Time Machine menu from the Mac menu bar and then hold down the OPTION / ALT key
- Choose “Verify Backups” from the menu options
It may take a while to verify the backup, depending on the size of the backup itself as well as the speed of the Mac.
Time Machine will verify the backup by comparing checksums, and it will alert the user if a problem or issue has been found. If the backup verifies fine, no issues will be reported. It’s possible the checksums will not match, indicating some sort of issue, corruption, or modification with the Time Machine backup, and Mac OS will offer instructions to attempt to correct the problem. It’s also possible the backup won’t have a valid checksum at all.
You can verify either unencrypted and encrypted backups this way.
While the Verify Time Machine backups feature has existed for a long time in Mac OS X and Mac OS, it’s important to note that only modern versions of Mac OS maintain a record of checksums associated with each backup snapshot, so if the backup was made prior to 10.12 or 10.11 it can not be verified by comparing the checksum this way.
Verifying Time Machine Backups from the Command Line
Command line users can also verify backups with the helpful tmutil utility, using the following command syntax:
tmutil verifychecksums /path/to/backup
The tmutil verifychecksums approach offers the same functionality as the Time Machine menu option except via the command line.
For those wondering, the Time Machine Verify feature works by computing the checksum of the backup and comparing it against a checksum generated at the time the backup was originally made from the Mac, similar to how an md5 hash or sha1 checksum is often used to manually check data integrity.
Know of another way to verify Time Machine backups or another helpful use of this functionality? Let us know in the comments below.