External hard disc disappeared

antoniorocca Said:

"The terminal has found the disk. Unfortunately the answer to the command is: 'no such file or directory'. Then, applying the command force mount the answer is: 'unknown special file or file system'."

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Having read the above, some thoughts...

• Try Another Cable Cable and Port:

One simple solution would be to just use another cable. Also, clean out the port, and use another port. It may be seen and accessible by that.

• Plug this into a PC with MS Windows:

Seeing 'unknown special file or file system', I am curious if it is formatted for a PC with MS Windows.

• Reset your SMC and NVRAM:

Sometimes, changes are made and performances are made, and the made becomes disrupted, technically. So, Reset the SMC and then Reset the NVRAM. Try all this once more.

• Try First Aid in Recovery Mode:

Boot into Recovery Mode: Hold down: [command + R) upon boot. Select your language, and then see if the disk is even seen. If it is, then select the disk, then click and run First Aid. See if this fixes the problem.

• Recovering the Data:

If not, it is probably a dead drive. So, take it to an AASP, and see if they can recover the data. Use this Link: Apple Authorized Service Providers - Apple Authorized Reseller

antoniorocca Said:

”May be I am really wrong in asking this, however, could the problem depend on the new version OS10.13.6 just installed?

Following the above, we can say it safe to disconnect from the computer all external devices before upgrading or updating the OS.”

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You are welcome.🙂

• What’s Next:

With everything you mentioned in your above reply, a few more notes and some info on what to do next.

• Blinking Light on External HD:

If the light is blinking, then, yes, it is indeed reading/writing something. So, rid of any security software you have installed on your Mac, as it may be continuously scanning for items.

• Turn Off Automatic Backups in TM:

Also, be certain that you turn off Automatic Backups on Time Machine; select to backup manually. If it was backing up continuously, then it may have been interrupted, and that would be the reason for so much storage space, and a corrupt backup.

• Disconnect All External Devices:

And yes: it is safe disconnect from the computer all external devices before upgrading or updatiing the OS. But if it were a tower, rather than a laptop, then you would, of course, want to keep the keyboard and mouse connected.

• When to Create TM Backups:

Whenever you perform installations, updates, and upgrades, always create a Time Machine backup prior to doing so, that way you can have something to Restore from, should the installation fail or not go as desired.

• Get a New External Hard Drive of SSD:

With all these troubles, start with a new external hard drive for backing items up. Be certain to get an external hard drive. And be certain to get a drive that is of Solid State Drive (SSD) type and High Sierra Compatible. SSDs have no moving parts, making then less prone to failure. Also, they read and write faster, meaning heat should not intensify as fast.

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• So, what’s Next, in Brief:

In all, I’d say reinstall their operating system. Backup your disk with Time Machine prior to the reinstall, as you always should. Erase the hard drive, then reinstall it anew, all using a USB Bootable Installer (Se Below).

• So, In Depth, your Next Steps are to:

1. Get a new, external SSD hard drive
2. Set TM Backups to Manual Backup
3. Create a Time Machine Backup of Your Current Installation on the new external SSD
4. Create a USB Bootable Installer
5. Boot into Recovery Mode
6. Erase the internal hard drive completely.
7. Format the internal drove with mac OS(Journalized)
8. Install High Sierra using the USB Bootable Installer you created in step 3
9. Use Migration Assistant to move content to this new installation

• Report back how it all goes.

You’re welcome.

One more thing.... Try some Reading and Writing, to be assured it is usable.

1. Create a new, empty folder on the Desktop;
2. Drag and drop the folder to the external Hard Drive.
3. Rename the folder
4. Drag it back out onto the Desktop.
5. Create a new folder on the external hard drive.
6. Trash both new folders.

If successful, reading and writing on the external hard drive seems good, and you’re all set.

The TIme Machine disk may be beyond repair if you cannot get to mount.

Launch/Utilities/Terminal and copy & paste this command at the prompt:

diskutil list

Press return.

If it sees the disk, note the number of the disk (far left column) you want to mount.

Then, copy & paste this command:

mount /dev/(number of disk)

Put in the number no parenthesis.

Press Return.

Also might try

mount force /dev/(number of disk)

Glad the external disk reappeared. However it is disturbing that you went through that ordeal, and frankly, I would no longer trust that external drive. Whatever caused your problem may be "intermittent" and it may happen again. Since this is a backup drive, it is extremely important that it be very reliable.

I suggest that you obtain a new backup drive and starting backing up to that new drive. I would keep the old (problematic) one since it presumably has backups done previous to now, but I would say that until you get a new drive and complete a new backup, you do not have a reliable backup of your files.

Even better is to purchase two external drives and alternate Time Machine backups to them.

You're welcome!

I agree: I, myself, would just leave this disk as further spare copy.

Not that I can think of.