fsck_hfs and diskutil discrepancies

look carefully at the Names of the Volumes you are checking, and the methods you are using to scan them.

you are showing checks of:

dev/rdisk1s1 -- MacOS base system -- this is a downloaded Installer volume. You are using fsck_hfs do do this, which ONLY scans HFS Volumes, not partition data structures.

dev/disk0s2 -- Untitled -- not really sure what that is, but unlikely to be what you wish to be scanning. perhaps a blank drive you just added? you are using fsck_hfs to do this, which ONLY scans HFS Volumes.

disk0s2 -- appears to be scanning the entire disk0 drive, not any Volume in particular, using diskutil repairdisk function.

These completely disparate results are caused by using different tools on a disparate assortment of Drives, Volumes, and partitions. I see no fundamental discrepancies here -- you asked for different answers from tools with different capabilities, and you got what you asked for.

I am reminded of the description of unix terminal tools as a box packed with VERY sharp special-purpose tools. Reaching in and picking some up without careful study will likely cut your fingers off.

What exactly are you trying to accomplish?

The most thorough check of your boot drive can only be completed when you are not using the drive. But in the running system, you are always using it. There are two cases where you can do this. The simplest is to restart in Safe Mode. the kernel boots up, then checks the drive before finishing starting up the rest of MacOS.

The second is Recovery. In regular Recovery, the Recovery partition IS technically speaking in use, but Disk Utility will go ahead and check it anyway. In Internet Recovery, the disk is Not being used -- it does not even have to be present. The software creates a dozen RAM disks to use for its temporary files, and can check absolutely everything about the boot drive.

--------

As to your concern that a problem was reported, but when you re-booted to fix it, it was not detected:

Occasionally, a Minor problem with a Partition or Directory will get fixed the next time the drive is Mounted after a Restart. So a transitory report of a minor problem is not really remarkable. It seems to fix these minor problems automatically, without any additional intervention. The problem is not detected later because it has already been fixed.

"Unable to unmount volume for repair. Operation failed."

That message just says the disk is in use, so it cannot be repaired right now. It is not alarming in the slightest.

But in your initial posting, the third report it says it was fixed, doesn't it?

Disk Utility calls those exact lower level routines. If Disk Utility says the drive is OK, it is not because it is not checking, its because the problem did not show itself.

We worry when Disk Utility says, "Problems found, but Disk Utility cannot repair them. ERASE your drive and re-Install MacOS"

^--- Now THAT is something to worry about.

Do you have a Trusted backup? if you do, none of this should cause you to lose any sleep.

I don't have an answer, but a couple things that should help:

1. The error "Unable to unmount volume for repair. Operation failed." should be easy to avoid. Just unmount the volume before trying to run first aid on the volume. ( To understand why you got it, do a little reading on why volumes won't unmount, and it should become clear. )
2. Why would you expect similar results from running a command on rdisk1s1 that you get from running ones on disk0s2? That's what you've shown you've done. Do they refer to the same drive when booted in different modes?

(PS: I didn't notice the other answers when I posted mine.)

"Untitled" is a terrible name for the drive you use daily, because that is the default name that is created when Disk Utility does not know what else to call something. You should rename it to something more meaningful to you, or use the factory-default "Macintosh HD".

If you lose your drive entirely, Disk Utility might try to create something called Untitled out of the debris remaining. You will want to know when something like that is happening, and be able to use "Untitled" as a sign of deep trouble.