Error in First Aid

When you're in the Recovery volume and run First Aid are you able to unmount the volume you're wanting to fix?

If not select the volume in Disk Utility, click on the Unmount button. If that works then proceed with the First Aid.

About 1/4th the time immediately following the could not unouterror, a second run will work.

Run Disk First Aid from restore mode, if still not repaired make sure you have a g old backup then erase the drive.

Drive DX may give more insight to the health of the drive.

CJOnline wrote:

I cannot delete the local snapshots. I tried in terminal, but it errors.

Probably related. Ignore them.

You could try in Disk Utility. Select the Data volume and they will be in a pane titled, "APFS Snapshots."

There is a – button at the bottom of the window.

Those are all in Snapshots. Just delete them.

CJOnline wrote:

I have deleted the internal drive, and reinstalled fresh copy of macOS. But although the disk errors have gone, the fan is still running fast every few mins. I cleared any dust from the intake vents, and the outlet vent, but no change. I am running iStat Menus, and see the CPU cores are running around 70-100ºC and the fans up to 80-100% every few minutes - without running applications. This seems to indicate an internal hardware issue - maybe dust, or degraded thermal paste?

I am not sure why you are attributing such issues to hardware problems without direct evidence..

The VAST majority of such issue are cause by software issues.

Consider downloading and running this little "discovery" utility, Etrecheck. It changes NOTHING. Etrecheck was developed by a senior contributor here, and uses mostly system calls and simple tests to collect often-needed information.

it contains little tests for speeds of devices, CPU utilization, memory usage, energy usage and a digest of recent problems, in one easy to use package. it does not even need to be Installed. Because less can be learned when your Mac is running great, best time to run is when your problems are actually occurring, if possible.

if you follow the directions faithfully, its report (pre-laundered of all personally-identifiable information) can be "Shared" to the System ClipBoard, then Pasted into an ‘Additional Text’ window in a reply on the forums.

Use Etrecheck Pro for free:

http://Etrecheck.com

The amount of data you get can be daunting. If you POST your report, some Readers here are willing to look over those reports, and can provide valuable insights.

then start a reply on the forums, Click on the "additional text" icon, and PASTE

Thanks, I thought so, but was waiting for someone more expert.👍🏽😀