If you have an external drive that you use with your Mac, and provided it is in a format that your Mac can read, then you by default should be able to access all of the files on it. However, there may be times when you are either barred from opening or accessing files or folders, or performing actions like deleting files may result in errors.
These error can include simple confirmation requests such as “Are you sure you want to delete the item“, or be full barriers that state you do not have permissions to delete the item. Either way, these can be a frustration when attempting to manage files on your drives.
This issue happens because of filesystem permissions being enabled on an external drive, which are rules on a per-file and per-folder basis that grant access to specified users and groups. Permissions are generally reserved to set up security and privacy on permanent local volumes, but since external hard drives can be used as permanent local storage (consider a RAID array for managing a large data store), then permissions can also be set up on them.
To fix this problem, you just need to have OS X ignore permissions on the drive again, which can be done with the following steps:
- Locate your drive in the Finder by pressing Shift-Command-C and then selecting it.
- Press Command-i on the selected drive to get information on it.
- Click the lock and authenticate to make changes.
- Locate the checkbox to “Ignore ownership on this volume” and check it.
After authenticating, ensure this box is checked to ignore ownership on a volume you have mounted. This will only be available on drives that support permissions.
When done, you should be able to copy any file to and from the drive. Note that this will apply for all users of your system, so everyone using your Mac should now be able to access all files on the drive. In addition, note that if you have multiple drives then this will need to be done for each drive separately, as there is no central setting to ignore permissions on all attached volumes.
Keep in mind that filesystem permissions only apply to volume formats that support them, such as NTFS and Apple’s Mac OS Extended; however, quite often external drives are shipped formatted with FAT32, which does not support permissions, and therefore should not be affected by permissions problems. In this case, you will not see an available option to ignore permissions on the drive when you get information on it.
In the event that you are seeing these errors and warnings persist regardless of the status of the “Ignore Ownership” setting, then your drive’s formatting may be damaged and in need of repair. To check this, you can use Disk Utility or another drive management tool to verify and repair both the partition tables and formatting of the drive, and then try reading it again.
As a final note, since this issue has to do with filesystem permissions, you might be wondering about the Repair Permissions option in Disk Utility that is so prevalently recommended when troubleshooting problems in OS X; however, this only checks the permissions for files on your boot drive, and will not affect anything on an external drive.
If you have external drives with a version of OS X installed on them, turning on “Ignore Permissions” will prevent Disk Utility on your boot drive from repairing permissions on the external drives. For my business I maintain a number of external drives with OS X partitions on them so I have to insure that Ignore Permissions is turned off on all of them, on my boot drive and on the OS X partitions themselves, as I occasionally use one or another of them to do repair on the other drives as well as on my computers internal drive. This even holds true for any drive on which you may have a cloned backup of your system. The latter may be the only case where most people might run into the problem, but for this reason it could be even more difficult to figure out, “why can’t I repair permissions on my backup drive?” Of course if you don’t have an external bootable drive the issue won’t arise.
It should also be noted that if you turn Ignore Permission off for a drive, that condition won’t apply if you boot from another drive; you have to turn it off in every drive you may start up on and wish to use with Disk Utility.
And what about an external drive that is used as a Time Machine backup repository?
You cannot repair permissions on a Time Machine drive, internal or external. On my external Time Machine drive there is no option to ignore permissions in the Get Info window. Check yours to see if this is the case for you as well. The only permissions problem I’ve encountered with Time Machine is an instance where the system would not let me replace a file due to lack of authorization. The way to get around that is to add yourself to the permissions list for the file you want to replace.
Hi, I know this is bit late in adding things, but ticking ignore ownership didn’t help. But it did allow me to do was add administrators to the users with Read/Write permission. I couldn’t add administrators until I ticked ignore ownership. Then locked files I could not get rid of before, just disappeared. After that, I could un-tick ignore ownership and everything is back to ‘normal’. Well it worked for me!