ExFat External Hard Drive opens ReadOnly

What do you think you'll have to reformat all of your drives? Do you use these drives with a Windows machine also?

Have you tried the following:

How to reset the System Management Controller (SMC) on your Mac ...

Reset NVRAM or PRAM on your Mac - Apple Support

Just a note on formats: if you ever mighty want to move your Photos library to an external HD the exFAT format will not be compatible. You would be better of in the long run to reformat all of your drives to the format that is most compatible with your Mac as long as they are not needed to be access by a PC.

Hi,

I have a *similar* problem. After upgrading to Mojave on my Macbook Pro, my external hard drive is now read-only. Like yourself, the same external hard drive can be read/written on a different iMac (also Mojave). I've reformatted it to APFS on the Macbook Pro, set ignore ownership permission on the drive, but it's still read-only as far as Finder is concerned. Repair disk doesn't return any errors.

The drive was working fine before the Mojave update (it was only ever used for Time Machine). If I plug in different external drives used by my other Mac, these also show up as non writeable. Anything else I can try?

regards

Carl

Hi onlyCurious

On my Mojave-running macBook that can only *read* external disks, I note that FileVault is turned on. The macs I have that can read/write external disks don't have fileVault turned on.

In addition, on the macbook, if I try to manually mount the external drives,

I get a password box:

Carls-MacBook-Pro:~ carl$ sudo mount -u /dev/disk2s1
/Volumes/Seagate 1TB

Password:

Since the drive is brand new, and just formatted to ExFat, and not encrypted, I'm not sure what the password relates to. It's not my user password.

I also note that I am *not* able to turn off FileVault (I am an admin, and have unlocked the Security & Privacy/FileVault tab in system preferences). The dialog box says:

This feels like a Windows policy is being enforced, but I wasn't aware that this was a feature of macOS ...

regards

On my ExFAT Transcend 256MB JetDrive SD card which I am using as an additional storage, I was facing the same problem i.e. the card suddenly becoming "read-only". Unlike some of the users, I am on a stand-alone MBP and there was no network or company-wide policy.

I reset the NVRAM as per this procedure https://support.apple.com/en-us/HT204063 and the card went back in to read-write mode.

Just thought I would post this in case any stand-alone users read till the end of the thread. Hope this helps others.

Happy holidays.

Seems the disk is OK. Try connecting it. Does it work?

If you wish to reformat the drive you need to do the following. Backup first because the drive will be erased.

Erase & Install El Capitan or Later

If possible back up your files.

1. Restart the computer. Before or at the chime hold down the CommandandRkeys until the Apple logo appears. When the Utility Menu appears:
2. Select Disk Utility from the Utility Menu and click on Continue button.
3. After Disk Utility loads select the drive (out-dented entry with the mfgr.'s ID and size) from the side list.
4. Click on the Erase tab in the Disk Utility toolbar. A panel should drop down.
5. In the drop down panel set the partition scheme to GUID. Set the Format type to APFS (SSDs only) or Mac OS Extended (Journaled.)
6. Click on the Apply button and click on the Done button when it is activated.
7. Quit Disk Utility and return to the Utility Menu.
8. Select Install OS X and click on the Continue button.

This should then be ready to restart the computer with the current version of macOS. You can restore your file and data backups separately from the backup disk. If you have third-party apps I recommend restoring them from their original distribution media for safety.

It seems to be some macOS compatibility issues with your ex-FAT. Like you said it worked on another Mac correctly. Which macOS does your other Mac have? Kappy is correct, if you use your drive exclusively for Mac then get it MacOS Journaled formatted. Ex_Fat is good when you have to use the drive on Mac and Windows. Copy all the data from the drive and format it with APFS or HFS.

I can confirm that my employer (IBM) has manipulated my home computer which I also use to access company network and this causes this problem. I have removed this software and everything is now ok - I cannot use this computer to access my company network, but I can access my disks read/write. What I am very upset about is that I have not be informed that this would happen after upgrade to the latest apple OS :-( and thus this problem has caused many hours of research and concern!!