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External Hard Drives Changing Permissions to Read Only

Three of my USB external hard drives have suddenly changed to read only. One of the times I was trying to transfer/back-up the files from one drive that had changed to read only to another external. Suddenly the second drive changed permissions. Then after plugging a third external, that drive changed permissions. They all were working perfectly fine with my computer and I have only been using them on MACS. Any explanations? Could there be something wrong with my USB ports? Is it possible to have a virus of some sort?

Thank you!

MacBook Pro, Mac OS X (10.5.8)

Posted on Jan 7, 2011 8:02 AM

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Posted on Jan 23, 2011 9:19 PM

Here's the thing that every forum I see keeps ignoring: The drives ALL worked BEFORE this problem NTFS or not, we were able to Read and Write with NO problems until, magically, the drive turned to read only. I am using a WD 2TB External USB Hard Drive. I have never formatted it, only used it right out the the box. I have PC's running XP, Vista, and Windows 7, and I have my Macs running OSX.

I have been Successfully transferring data between all of the computers with no problems until today. I transferred data literally 3 days ago from my Mac to my PC AND from my PC to my Mac using this drive. I always use the eject option on the drive. NTFS or not it DOESN'T matter. The issue is drives that worked with no issue suddenly becoming useless. Sadly this looks to be an issue with the Mac OS.

If we could get some true discussion and assistance on the root of the problem, or a patch from Apple, this would be great. I am not sure what is causing this but apparently it is no isolated incident as everyone is going form working to non-working without changing any settings.
87 replies

Dec 30, 2011 1:37 AM in response to leelee15

Hello everyone... before I make a complete fool of myself I just wanted to say that I am a complete noob when it comes to these things so please be gentle 🙂


I suddenly had the same problem where my external HD changed permissions to read only (it has been working fine for the past 3 months). Under the "Get info" tab "Sharing & Permissions" section it only reads "you can only read" with no other info. No mention of the users or any other info and I can't click or hit anything (other than my head against the wall!!!!) If I try the Desktop Utilities route my Macbook Air recognizes the eternal hard drive but all buttons such as "verify Disk" etc are greyed out... no idea what I should do. Tried logging out of my user account and back in, tried ejecting and reconnecting but everything has failed.


Anyone with any ideas?! please need any help I can get. Thanks!

Feb 9, 2012 6:07 PM in response to beatlelili

Very simply, I discovered the other day that several of the Firewire drives in my chain had become "Read Only" drives.


Searched the internet for an answer and landed here.


This has never happened to me before in all my years of owning and using Macs. (Since 1988)


The solution for me was simply opening Disk Utility and Verifying the disk(s) in question.


Each time I Verfiied the problem was corrected.


I tried the other suggestion of using Terminal and doing that fancy foot work thing. It did not work for me. Tried it on 2 drives....Nothing happened.


Verify using Disk Utility and let me know what happens.

Mar 5, 2012 9:33 PM in response to beatlelili

Dear friends,


I am facing a problem with my External HDD formatted in FAT32 file system.

I have an external HDD that is formatted in FAT32 file system and I want to share this drive on my network so that my other MAC user can access this external drive.


I have two MAC mini with OSX 10.6 and 10.7.3 and one MAC Book pro with 10.7.3. All are on same network able to see each other share Drives. But they are only able to access the Public folders of all the users and Internal HDD of all the MAC books. They are also able to see shared external HDD but no one is able to open that external drive over network. Only the MAC book with external drive is directly connected is able to open it and make file and folder in that.


I have also noticed one issue with this external HDD whenever I try to share this drive via file sharing option its user permission is not highlighted.


Could anyone help on this matter how could I access this drive from other MAC book.


Please revert on my post if any have any suggestion on my problem.

Apr 17, 2012 6:46 PM in response to beatlelili

Thanks for the tips. Verifying at Disc Utilities helped for me as well. At first though it said that I had to restore the HD, which I didn't want to do for I didn't know what the consequences would be. Then I closed the program and opened it again for I was curious what it would say now. But then it said nothing about restoring anything and I found out I could write again on the HD. Good luck everyone. Thanks again.

Apr 17, 2012 10:47 PM in response to Institian

I am (have been) having this same issue for over a month. I have three hard drives on my iMac. 500 GB Internal HD, 1 2 TB External asting as a Time Machine Backup, and 1 2 YB External with Lion installed, along with tons of music, apps, data files etc. These have all been working fine the last week or so since the mysterious Read Only locks at least two of my three disks (not always the same ones). I have done all the standard stuff, Disk Utility to Repair the Disks, running Repair Permissions, a couple of times even going into the Terminal and going through the Repair Home Folder Permissions routine. I'm never sure what fixes the problem, only that as suddenly as it starts, it goes away the next day or so.


Tonight, Time Machine is Read Only... AGAIN, and my Lion Hard Drive is ALSO Read Only... AGAIN.

I ran through the SAME proceedure on these two hard drives tonight - 1.) Disk Utility, Click the drive in question in the Left Column in Disk Utility, then choose Repair in the Right Column. That completed, I ran Repair Permissions. Did the SAME to both disks. Time Machine is now BACK and writeable again, but the other HD is still Read Only.


I'm going to Shutdown, Reboot, and check the Permissions again...

Apr 17, 2012 11:12 PM in response to Vic Schmidt

After I Shutdown and re-Booted, the Lion HD showed up greyed out in Get Info - could do NOTHING with it, Disk Utility, etc. Noted that each time I've had these issues, my iPhone 4 is always plugged in also (I take advantage of my time on the iMac to re-charge the iPhone battery). On a lark, I un-plugged the iPhone and it's cable from the iMac. No change. The Lion HD was showing up in Disk Utility as greyed out as I said earlier. For the heck of it, I used Disk Utility to UNMOUNT the Lion HD, then used Disk Utility to Mount it again... it immediately showed up as available in the Disk Utility, went ahead and just ran Repair Permissions (before I checked the Read / Write permissions) and when it finished repairing permissions, I checked permissions again, and IT IS BACK IN THE LAND OF THE LIVING, Sharing & Permissions in Get Info once again say "You can read and write"...


Now, WHY does it do this (as it happens at least a couple times a week? DOES the fact that the iPhone is plugged in have something to do with it? Something to watch for I guess...

Apr 30, 2012 1:45 PM in response to Vic Schmidt

The problem may be an erroneous flag for the volume of the external drive that puts it in read-only mode. When I had a similar problem, the following steps corrected it.


1. Open Disk Utility and Verify the Volume.


2. If the verification shows that the volume is OK. If so, run repair disk. If the verification does not show that the volume is OK, STOP. Copy the drive immediately to another drive before proceeding. Failure to do so can result in permanent data loss.


3. After the repair function completes, close Disk Utility and check the status of the volume. Running verify or verify and disk repair didn't fix the problem for me. If your volume still shows that it is read only, start Terminal. It is located in the System Utilities. Type in the following command follwed by the name of the affected volume:


sudo chflags nouchg /Volumes/[Volume Name]


For example, assume your external drives are named Mary X where X is a sequential Arabic numeral. The command line for one of those volumes will be "sudo chflags nouchg /Volumes/Mary\ X" where X is the drive number. You will be prompted for your administrator's password. Note that when you type in the password, it will not be echoed in the terminal window for security reasons . Press "Return"


If your experience is similar to mine, your external drive will no longer be in read-only mode. Hope this is helpful.

Apr 30, 2012 1:52 PM in response to Mika77

Mika77 wrote:


In disk utility I had a look. I cannot verify or set permission (greyed out). The data coming back from info. How can I change this??
Name : FUJITSU MHZ2320BH G1 Media
Type : Disk

Partition Map Scheme : Master Boot Record
Disk Identifier : disk2
Media Name : FUJITSU MHZ2320BH G1 Media
Media Type : Generic
Connection Bus : USB
USB Serial Number : 560A48A291F9
Device Tree : /PCI0/EHC1@1D,7/@3:0
Writable : Yes
Ejectable : Yes
Mac OS 9 Drivers Installed : No
Location : External
Total Capacity : 298,1 GB (320.072.933.376 Bytes)
S.M.A.R.T. Status : Not Supported
Disk Number : 2
Partition Number : 0


Name : NieuwVolume
Type : Volume

Disk Identifier : disk2s1
Mount Point : /Volumes/NieuwVolume
File System : Windows NT File System (NTFS)
Connection Bus : USB
Device Tree : /PCI0/EHC1@1D,7/@3:1
Writable : No
Universal Unique Identifier : C7B58C48-D6BC-4078-9DAE-CB125901A4D6
Capacity : 298,1 GB (320.070.288.384 Bytes)
Free Space : 127,1 GB (136.438.530.048 Bytes)
Used : 171,0 GB (183.631.757.312 Bytes)
Number of Files : 85.578
Number of Folders : 0
Owners Enabled : No
Can Turn Owners Off : No
Can Be Formatted : No
Bootable : No
Supports Journaling : No
Journaled : No
Disk Number : 2
Partition Number : 1

That drive is formatted for Windows (NTFS) Macs can not write to it unless you reformat to FAT32 or HFS

External Hard Drives Changing Permissions to Read Only

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