Why is my Mac hard drive suddenly read-only?

Hi Dave, I am running Mac OS X 10.3.9 and recently encountered a strange occurrence. Instead of the usual tag under my main hard drive(74.4 GB, 24.75 GB used) it shows (74.4 GB). After I used "Get Info" it says i have read-only access. Every time i want to move a file to it, it asks for my admin password. I am normally an admin user, and this has never happened before. Is this a major thing? And how can i change it back to what it was before?

Dave's Answer:

That's a very strange occurrence, I agree with you. The good news is that one of the standard administrative applications included with Mac OS X will doubtless fix what's happened on your disk, which is that a folder permission has somehow been messed up.

The program you need is Disk Utility and you can find it in Applications --> Utilities --> Disk Utility. Then simply select the drive you want to fix:

Click for full size screenshot

In this case, "X" is my boot drive, and "X2" is my backup drive. I clicked on the "X" drive, then on the button Repair Disk Permissions.

Now the utility will go through the entire file system, making sure that the access permissions and ownership of each major directory matches the recommended configuration from Apple. It'll take a few minutes, during which time you'll see information like:

Finally, it'll be done and I bet your problem will be fixed!

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Categorized: Mac OS X Help (Article 6396, Written by Dave Taylor)
Tagged: disk troubleshooting, mac os x, repairing permissions
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Reader Comments To Date: 44

paul miller said, on June 9, 2006 6:59 AM:

I tried this and it didn't work. Not complaining, I appreciate free advice, but I though you'd like to know.

Oliver Tappin said, on April 25, 2007 1:00 PM:

I have an external hard disk drive that is 400gb and it says read only for the mac but it lets me edit files on it on my pc!? Any help would be really appreciated.

Ollie said, on May 20, 2007 11:59 AM:

Hello there, i agree with davem you do need to format it but its also to do with fat32 and NFTS! Macintosh computers only work woth fat32 and windows have come up with their one that they have made which is much faster which is called NFTS. If you want to use your external hdd with mac and pc, then you need to format it on the mac, which will automaticly put it to fat32 but if you format it on pc, make sure it is set to fat32 and NOT NFTS. NFTS only works with windows, even though its really fast and works well, fat32 works with mac and pc. If you have any problems, i would be happy to help. Hope that helps anyone here!

roberto said, on May 30, 2007 10:03 PM:

i can no find my hard drive
my hard drive is lost

Matt said, on August 15, 2007 7:27 AM:

Is there a way of making it FAT32 without loosing all your data on the hard drive?

Mike said, on January 24, 2008 2:13 PM:

Hi,

I have the exact same problem,
My 'Repair disc permissions' is greyed out..

Any Ideas..?

Aditya said, on January 25, 2008 9:08 AM:

Hi ,I am Aditya from India .I have a problem that I am unable to solve and know the root cause.My system stops suddenly (while browsing ,listening music ...etc)i.e just like a movie been paused ,then i restart my system using power switch.It just shows a blank screen and my hard disk makes a kink sound at the beginning and then it goes on reading and reading but blank screen remains.
My details: Motherboard Intel 915GAV ,
Processor Intel 2.8GHz HT, HDD :Seagate Sata ST3160215AS_____________________________3.AAD___\5&30D26B9&0&0.0.0
RAM: 512MB . OS :XP+sp2
3 years old and motherboard been replaced twice due to above reason.
I have removed my cables and then reconnected and the problem is solved ,but at times I have to reconnect more than 10 times and even 2 days .Then it starting booting and starts normally .I am unable to know the root cause .I am regularly installing latest OS after 6 months.

Scott Wild said, on February 12, 2008 10:49 AM:

This was all great, until the Restore button was greyed out.

Your advice was simple and clear, just left me at a dead end.

You can email an answer if you figure it out at rswild@gmail.com

Thanks,

Scott Wild

david said, on February 23, 2009 1:50 PM:

FYI fat32 is only good for 2 gigs

but on the reformating thing...windows only lets mac read its files (nfts), not write...that includes washing it down(for older systems anyway)...ik i can on leopard...

but for sharing..well i like to keep my dirty mp3s on the mac cuz it can take it, analog record to windows and save on a dif partition on my exhd...then ik its clean 4 good lol

but yea...discs work 2

Ryan said, on March 21, 2009 2:17 PM:

What David REALLY meant to say is that fat32 is only good up to 4 gigs PER FILE( NOT PARTITION!)

Otherwise anyone that buys a Western Digital portable hard drive will be confused why their 100+ gig hdd is fat32...

But I did find these comments useful. Didn't know ntfs(not nfts, as others put it lol) wasn't writeable on a Mac. It confused me because it works in both Windows and Linux... in Linux it shows that my hdd has 777 file permissions, but when I mounted it on my Mac it only had 755.

j said, on May 9, 2009 4:31 PM:

hi!

i have a problem... I was trying to lock my macintosh hd and accidentally placed read only for the admin then locked it. i later realised what a disaster it was and decided to restart my laptop. when i turned it on the screen was blank and just loading for almost an hour. i repeatedly restarted it for the day but it wont go to the actual desktop. my laptop has a login and password requirement to get to the desktop. please help me!thanks

Bernard said, on June 26, 2009 6:18 AM:

Hi Dave,

I have the Final Cut Express 4 software on my imac.Have tried to configure my external drive but am getting the message "unable to set scratch disc.the selected directory is on write protected or non-writable media"
How can I go about configuring it? A step by step explanation will be appreciated very much.

Bernard

another dave said, on November 3, 2009 9:18 AM:

I just wanted to add how to do this from the terminal since this site gets all kinds of hits

Machine will not load OS. Reboot
While starting up hold APPLE-S until you see it in a command prompt.

Follow the instructions provided to mount your Volume (doesn't work unless you mount it;)

Now follow the rest:

Type
cd /Volumes
and press enter

Type the command
chmod 755 Macintosh\ HD/
and press enter

sudo chmod -RN /Volumes/"Macintosh HD"/Users/USERNAME
sudo chown -R USERNAME /Volumes/"Macintosh HD"/Users/USERNAME

Please share this with everyone, it's worked a dozen times for me. Apple needs to make it so that we can't mess up an OS from the preferences pane.

Milton Herrera said, on November 10, 2009 4:59 PM:

i have mac osx tiger and my ibook g4 keeps going into the single-user mode and im not able to get it out of there and start my laptop normally how do i get out of this and make sure it does not go back in there?

Abhijith Devatha said, on January 23, 2010 12:20 AM:

So to put it in simple terms

FAT 32 - Works with Mac and PC
NTFS - Works with PC, but Read-only in Mac

FAT 32 - Cannot transfer files > 4 GB
NTFS - Any Size

Final Verdict - You can't have both at the same time.

Am I missing anything?

Ken Benson said, on May 2, 2010 11:19 AM:

Your answer didn't work. I can see the hard drive on Disk utility, but I can't select it... Ken

michele said, on May 23, 2010 10:06 AM:

Hi,
Brilliant, worked straight away. Thanks so much for the help.

Suwandi said, on May 28, 2010 10:16 AM:

Hi there,
I'm also facing the same problem here. I've tried all following command, but the messages are still the same, that the file is read-only.
I also tried to startup using single-user mode, but It stops and shows IO error.
chmod 755 Macintosh\ HD/
sudo chmod -RN /Volumes/"Macintosh HD"/Users/USERNAME
chmod: suwandi 1/: Read-only file system
.....

chmod: Failed to clear ACL on file suwandi 1/Users/suwandi: Read-only file system
....

sudo chown -R USERNAME /Volumes/"Macintosh HD"/Users/USERNAME
chown: suwandi 1/Users/suwandi/#.profile#: Read-only file system
.....

Please let me know if you have the solutions

Rohain Arora said, on June 17, 2010 2:23 PM:

the repair is shaded out, i cant click on it.

Please can you suggest me soemthing!

Kitty said, on August 2, 2010 12:28 PM:

this command sudo chmod -RN /Volumes/"Macintosh HD"/Users/USERNAME
sudo chown -R USERNAME /Volumes/"Macintosh HD"/Users/USERNAME i did in terminal on a macbook pro i made internal boot drive read only. What do after I put command in. it doesn't change or reboot? I tried commands to exit it stays in black screen single mode. please advise.Thanks

Graham Leask said, on October 25, 2010 2:50 AM:

SAme problem - repair option greyed out.

How do I get round this?

Daleon said, on November 1, 2010 7:47 PM:

Thanks you for the awesome insight Dave....!

Gary said, on November 12, 2010 4:35 PM:

I opened up the disk utility but it doesnt give me the option to verify disk permissions or repair disk permissions. Those buttons are unclickable. Help please??

Maria Samkary said, on January 1, 2011 7:55 AM:

Hi , My 'Repair disc permissions' is greyed out..

Any Ideas..?

Shell said, on January 2, 2011 5:57 PM:

Ok I had the same problem "Repair disc Permission is greyed out" As long as you are confident you want to delete everything, click on the erase tab in desk utilities, then click on erase. This erased everything from my external WD hard drive as I wanted.

Gary said, on January 14, 2011 3:42 PM:

I have tried the following: Disk Utility - Restore button was greyed out. Then I tried the following commands:

sudo chmod -RN /Volumes/....
I received the following error messages (one per file in the volume):

chmod: Failed to clear ACL on file IMG_0010.jpg: Read-only file system

I then tried
sudo chown -R USERNAME /Volumes/....
I received the following error messages (one per file in the volume):

chown: /volumes/Untitled/IMG_0011.jpg: Read-only file system

It is an SD card where I put a bunch of images onto it for a digital picture frame. After putting it in the frame I wanted to add files to the SD card and this is what I get. No, the SD card is not locked.

Any ideas???

Anu said, on April 2, 2011 12:40 PM:

fixed mine like this,right-click wd icon in computer folder,then press properties-tools-check now-start ok. should work 100%.other solutions are useless.

Anu said, on August 10, 2011 3:45 PM:

I am facing a similar issue. I can move, delete filed from my primary HD but when I see the permissions in the "get info" on my HD, it says read only. Is it the way it is suppose to be? As far as i remember, i was read & write the last time I saw it. I tried the repair disk permissions thing, it did that but still my HD is in read only mode.

I have another basic doubt, I understood your terminal method but havent tried it because I am wary as the complete steps are not given. I am first time mac user and would appreciate if you could give me all the steps that are to be done on the terminal.

Amy said, on September 27, 2011 1:57 PM:

You have to transfer the stuff you want to keep off of the external drive first. Then open Utilities in your Applications folder, open Disk Utilities. Format (Erase) the drive in Fat32. Put the stuff back on it, it should work.

Jacqueline said, on October 7, 2011 10:16 AM:

i went to go do this but the "Repair Disk Permissions" button wouldnt let me click it, it was all greyed out... :S

tony said, on October 11, 2011 7:08 AM:

I am having the same grayed out problem with a locked up external drive. Has this question been answered? I see lots of the same question but no link or method of getting Repair Disk Permissions ungrayed.

Dave Taylor said, on October 11, 2011 10:31 AM:

If you're having problems with the "Repair Disk" option being greyed out and unclickable, it's because Mac OS X thinks it's the boot drive. Boot off your original install / restore DVD (you don't have to install the OS, don't panic!) and choose Disk Utility. Then you should be able to fix it. Done? Reboot and you should be golden.

sam said, on December 10, 2011 6:41 AM:

My External Hard disk was powered and was abruptly powered off while transferring file. when i reconnected the HDD, it connected as readonly. Then i disconnected it and and connected it to windows and then properly ejected it. later when I connected it back to my mac, it worked great and restored all permissions.

Don said, on December 31, 2011 5:40 PM:

I have a similar issue as the OP, and on two separate Macs running OS X 10.7.2. If I want to copy items to or from my Hard disk, I must authenticate as myself, a logged in admin user. I have full rights to my home directory, but I cannot write to my hard disk unless I first authenticate. Hard disk owner is "System", r/w, Group is "Wheel" read only, "Everyone" is read only. Home Dir folder is owned by my name, the logged in admin user. I have ran permissions repair with both Onyx and Disk Utility to no avail. Is there a fairly easy way to correct this problem? I guarantee a SB Venti of your choice with correct answer :) Thanks in advance.

Dave Taylor said, on January 1, 2012 9:10 AM:

Don, hmmm.... can you open Terminal.app and type in "ls -ld ." to see what kind of permissions and ownership you have? Here's what I see:

$ : ls -ld .
drwx------+ 26 taylor staff 884 Jan 1 08:59 ./

Seems odd, as you say.

mt said, on January 16, 2012 1:43 PM:

hello, i have many questions actually.
they same this happened with me my hard drive is suddenly "read only" and i have opened disk utility but the "repair disk permission" button is greyed out and i cannot click on it, BUT i can click on the repair disk option. if i do will this erase all the data on my hard disk?
help please

Old_Enuf_to_Rmbr_DOS said, on February 26, 2012 3:53 PM:

Yes, Dave & other posters, very helpful. Sounds like we're in two groups, one being the NTFS crowd. I don't think I could give up NTFS format. I thought they'd worked out all the Windows compatibility issues.
WELL, my point for posting, to everyone who has this NTFS issue, DONT overlook the easy solution, for around $40 USD (or so), buy the VMWare Fusion, have a copy of WIn7 or XP running along side, you can then share the MAC folders, so Windows sees your mac folders/files as if they were windows, has both read & write access to it/them, then it already sees the expansion drive in "happy windows" mode. Obviously a little cumbersome, but it's flexible, as you don't have to keep track of what's formatted in FAT32. For all I know, there might be other enterprising companies making some utility, but Fusion is hard to beat!

Sanjeev said, on March 19, 2012 11:06 PM:

Hi Dave,
I have tried doing it with the install dvd for mac os , but still the repair disk remains greyed out, can you please help me with this as i am trying access external harddive and its showing in read only status.

Cheers
Sanjeev

Jonny Tanna said, on April 13, 2012 1:51 PM:

I read through this entire article and the best solution was sam's, I'll quote it below

Working Solution
-------------
My External Hard disk was powered and was abruptly powered off while transferring file. when i reconnected the HDD, it connected as readonly. Then i disconnected it and and connected it to windows and then properly ejected it. later when I connected it back to my mac, it worked great and restored all permissions.

Posted by: sam at December 10, 2011 6:41 AM

rosh said, on May 20, 2012 9:23 AM:

I had a file which was read-only, and like others the disk repair option was greyed out in Disk Utilities. I found a way around it in Disk Utilities by clicking on the drive I wanted to change and then clicking on the "convert" option at the top of the Disk Utilities screen. Where it says image format, change this to "read-write" and this seemed to work for me.

Robert said, on June 6, 2012 9:42 AM:

When I opened the disk utilities.... clicked on my USB disk, I didn't see any of options near the bottom of the window about disk permissions. Then, after pushing a few buttons... I was able to get to where they appeared in the window, however, I was not able to click on them.

What's the problem? I had used the disk before on my Mac (first)... then, I had to print off some documents and the only computer I have access to with a printer is a PC. Ever since I had plugged it into the PC to make print some things off... I could only use it as read only on my Mac.

EFFING_PISSED said, on August 15, 2012 6:01 AM:

SERIOUSLY! You should also mentioned that by following these steps, EVERYTHING in the external hard disk WILL BE ERASED!!! Now all my files are GONE! & it costs a bomb to retrieve them. "Thanks" MAN!

Gopi said, on September 24, 2012 11:01 AM:

had same probs ...

ur solution did te magic !!! thanks a lot !!!!

hilashus said, on January 13, 2013 7:49 PM:

i had the same problem and i tried what you said but didn't work ?

I do have a lot to say, and questions of my own for that matter, but first I'd like to say thank you, Dave, for all your helpful information by buying you a cup of coffee!

I do have a comment, now that you mention it!

Why is my Mac hard drive suddenly read-only?

Reader Comments To Date: 44

I do have a comment, now that you mention it!

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