Home » Questions » Computers [ Ask a new question ]

Verifying Time Machine backups

Verifying Time Machine backups

I'm preparing my system for a Snow Leopard upgrade, and I prepare for the worst case scenario: full reinstall and restore.

Asked by: Guest | Views: 64
Total answers/comments: 5
Guest [Entry]

"Time Machine does not have any built-in mechanism to verify a set of backups as being valid. That's one issue with Time Machine, being consumer orientated instead of enterprise...

Performing a Disk Repair in Disk Utility doesn't validate the Time Machine backup data, but will verify the structure and integrity of the backup disk. (Of course, Disk Warrior verifies / repairs in a complementary manner).

The only way that I see that you could verify the data in the backup is to do a full restore.

Please note, you can open the Console logs, and filter against BACKUPD to see what happens during a backup, and see if any error conditions occurred.

Edit:

Time Machine does include an option, if you hold down the option key and click on the Time Machine menu bar add-on, to ""Verify backups"".

This does not verify the contents of the backup. In other words, that backed up file abcd.txt is the same as abcd.txt, instead this verifies that the Disk image the time machine data is not damaged.

Take a look at http://support.apple.com/kb/HT4076"
Guest [Entry]

"As per Mac OS X 10.6.4, you can initiate a verification of your backup by option-clicking the Time Machine icon in the menu bar.

I'm not sure what exactly is verified, but when I did it, Time Machine recommended that I start a new backup to improve reliability.

Further reading: Apple knowledgebase article."
Guest [Entry]

"Here is an overview of the current options available in 2021 for verifying Time Machine backups.

As of Mac OS 10.11, Time Machine computes file checksums and stores this information in the extended attributes of the snapshot files. You can verify these checksums using the tmutil verifychecksums command. The command will output any files with invalid or non-matching checksums at the specified path. This may require root permissions. Further reading: apple.stackexchange.com/questions/255388/how-do-time-machines-checksums-work

You can compare a backup to the files on your computer using tmutil compare. See the tmutil man page for more info on this command. See also: apple.stackexchange.com/questions/19453/how-is-it-possible-to-compare-files-on-your-hard-drive-with-those-in-your-time

For network drives, there is a hidden option in the Time Machine status menu to verify backups. To access this option, click on the time machine menu bar icon, press and hold Option, and click ""Verify Backups"". It's not clear exactly what this does, but some have speculated it is using fsck to verify the integrity of the disk image. See: support.apple.com/guide/mac-help/verify-your-backup-disk-mh26840/mac

You can use Disk Utility to verify the integrity of the backup volume. Select the disk and click the ""First Aid"" button. This will check the filesystem for errors and attempt to repair them. You can also use the diskutil verifyVolume command in the terminal. See: support.apple.com/guide/disk-utility/repair-a-storage-device-dskutl1040/mac"
Guest [Entry]

"Doing a Time Machine backup to a network-based share is known to be more risky and fraught with problems. So, if you really, really, do not want to run the risk of hitting trouble with your upgrade and then having further trouble getting back to where you were then I would strongly recommend temporarily using a local disk and a tool like ShirtPocket's SuperDuper! or Carbon Copy Cloner

For just brute-force verifying your data, however, I think the best you can do is to manually mount the sparsebundle on your network drive, and use something as simple as 'diff -cr' to compare the bulk of the files from the 'Latest' version against your system drive (which is obviously going to throw up some that have changed since TimeMachine last ran.)"
Guest [Entry]

Check out BackupLoupe – it gives you some great ways to navigate across your Time Machine backups.