What is the best way to validate every single file on an external drive?

[yalag]

My mac is having a kernel panic every time I try to time machine this external drive.
I've tried disk utility but I'm pretty sure it doesn't actually check for much, except maybe for some directory structure. The scan is maybe only a few minutes long and it reports everything has fine.
Is there a command or app that will actually read every single file in the disk and report any corruption or IO error?

 

[barbu]

You could try disk warrior IF you are using HFS rather than apfs.

 

[Fishrrman]

What kind of report do you get if you run disk utility on the tm backup?

If your goal is to copy the contents of one external drive to a second external drive, the best way to do it is by using a cloning app such as CarbonCopyCloner or SuperDuper.

The second drive will then be AN EXACT COPY of the source.
You can connect it and use it just as you would the source drive (if the source drive fails).

 

[yalag]

I tried disk warrior but I dont see an option for checking files? It just wants to rebuild the directory?

 

[barbu]

Yes that’s likely what you want. You should be able to preview the changes it will make. You could make a full copy of your disk before if you are exceptionally cautious, but DW works well.