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“Try repairing your disk permissions” is a standard Mac troubleshooting tip that’s been going around forever. There are actually two different tools for repairing different types of disk permissions, and one of them is very hidden.

The permissions here are really file and directory permissions, but they’re generally called “disk permissions.” Your Mac won’t automatically repair permissions except while installing or upgrading Mac OS X itself.

Update: As of Mac OS X 10.11 El Capitan, the Disk Utility in Mac OS X no longer includes a way to repair Disk Permissions. This is no longer necessary thanks to System Integrity Protection.

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What Are Permissions, and What Does Repairing Them Do?

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Like on other operating systems, including Windows and Linux, files and directories on a Mac each have their own permissions. The permissions control which users and system processes have access to the files, and what they can do. For example, system files are marked read-only so normal user programs can’t modify them. Executable files must be marked as executable or the system won’t allow them to run.

The permission system is a way Mac OS X and other operating systems ensure security. A program you run on your desktop can’t just modify your system files without permission. If you have multiple user accounts on your Mac, permissions keep each user account’s files private from other uses.

Macs have two different types of permissions. There are standard UNIX file permissions, the same sort of permissions you’d find on Linux. There are also more modern access control list (ACL) permissions. You can view a file or directory’s permissions by holding Ctrl and clicking the file or directory in the Finder, clicking Get Info, and looking under Sharing & Permissions

Your Mac contains a database of permissions. The database is stored in “Bill of Materials” files inside the /var/db/receipts and /Library/Receipts folders. Mac OS X system files and third-party applications installed from .pkg files leave .bom files here, and the files list which permissions the system files or program files should have.

When you repair permissions, your Mac looks at the .bom files here and checks the actual files on your system. If a file or folder on your system has permissions that don’t match the permissions specified in the .bom files, your Mac will change the permissions to match those in the .bom files.

Note that this doesn’t apply to all files on your system. Your personal data files don’t have any entries in the permissions database, and third-party applications that don’t use .pkg files won’t be represented in the database. The permissions-fixing operation will leave all these other files alone.

When Should You Repair Permissions?

During the normal use of your system, it’s possible that programs will change file or folder permissions from their original ones. It’s possible that these new permissions will then cause problems. For example, a program might incorrectly assign write permissions to system files, reducing security by allowing normal user programs to modify them. A program might make a program file not-executable, preventing an application from running. A program might accidentally give your user account read-only access to your home folder, preventing you from saving or modifying any files.

There are many problems that can be caused by incorrect — or “damaged” — permissions. Repairing your file permissions is also a safe operation. The repair process shouldn’t cause any problems. That’s why repairing your Mac’s permissions is one of the first troubleshooting tips you’ll get if you have a problem with your Mac.

If you’re not having trouble with your Mac, you shouldn’t need to repair permissions. If you’re having some sort of problem, repairing your permissions is a good, safe place to start.

How to Repair Disk Permissions

You can repair your Mac’s permissions from the Disk Utility application. To open it, press Command + Space to open Spotlight search, type Disk Utility, and press Enter.

Select your Mac’s system partition — generally “Macintosh HD.” Click the Verify Disk Permissions button if you’d like to check your permissions for problems. Click Repair Disk Permissions to check for problems and automatically fix them.

Note that it’s normal for some permissions to change in normal use of your system, and this doesn’t always cause problems. You’ll probably see some incorrect permissions even if there’s nothing wrong with your Mac. This is nothing to worry about. We saw quite a few incorrect permissions on our Mac, but it wasn’t misbehaving at all. They weren’t really a problem.

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That’s it — your permissions will be repaired. If your Mac is experiencing such severe problems that it won’t boot normally, you can also access the Disk Utility from OS X Recovery and repair disk permissions from there. Your Mac also automatically runs a disk permission repair when your install Mac OS X on top of an existing Mac OS X installation, so reinstalling or upgrading your Mac operating system should also fix disk permissions problems.

How to Repair Home Directory Permissions

There’s also a second tool that repairs some permissions. This repair tool will repair your user account’s home directory permissions. If you’re having problems with your user account’s files — perhaps you can’t save any files to your home directory, possibly because it’s been made read-only — you can use this tool.

This tool doesn’t use .bom files to adjust system file permissions, it just repairs a user account’s home directory to the standard, default permissions.

To do this, enter OS X Recovery by restarting your Mac and holding Command + R. In the Recovery environment, click Utilities on the menu bar and select Terminal. Type resetpassword into the Terminal and press Enter. Click your Mac’s hard drive and select the user account that’s experiencing problems.

At the bottom of the window, click the Reset button under Reset Home Directory Permissions and ACLs. This will just reset the user account’s permissions, not its password.

Restart your Mac when you’re done. The user account’s home directory permissions will now be repaired.

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Repairing your Mac’s permissions shouldn’t be a mandatory, regular system maintenance task. It will only help if you’re actually experiencing a problem, so there’s no reason to run this tool regularly. On the other hand, this is a safe operation, so there’s no danger in repairing disk permissions if you think it might help.

Image Credit: Karlis Dambrans on Flickr

1. Disk Drill

Disk Drill is the free top data recovery app for Mac OS X. Disk Drill Basic, in addition to having previewing capabilities for recovered files, contains several other functionalities, such as Recovery Vault and Guaranteed Recovery, lost partition restoration, boot disk maker and so on, which make it one of the best Mac data recovery software applications available.

Disk Drill works on internal and external hard drives, USB flash drives, SD cards and many other appliances that can be connected to a Mac, including iOS and Android devices. Its last version has an extensive database of file signatures that can be restored from drives even after formatting and uses very efficient and fast scanning algorithms.

Disk Drill is constantly updated and supported by its ever-growing team and covers cases of data corruption resulting from loss of power, or removal of a device without first unmounting it.

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Free Features:

#1 Recovery Vault is an advanced extra layer to the Trash Bin that keeps a reference to deleted data.

#2 Guaranteed Recovery is a background service that saves a copy of each file to a user-specified folder. Both data protection modules substantially reduce the possibilities of permanently losing critical data.

#3Data Backup feature provides users with the ability to recover lost data from a byte-to-byte clone version of the device/partition, without having to risk the original storage source.

#4 In addition to that, multiple extra tools like Duplicate File Finder, Disk Health Monitor, Disk Space Analyzer, Emergency Recovery Boot Drive, are available for free.

The user interface is very friendly, and the Pro version includes an effective support service and a lifetime-upgrade option that covers every new version. Disk Drill successfully manages the balance of essential and advanced features for the casual, professional and enterprise users alike, that makes it worth the money spent on the upgrade. There’s something in Disk Drill for Mac Enterprise that even forensic experts and law enforcement organizations will find useful.

2. PhotoRec

PhotoRec is not the most powerful free Mac data recovery tool, but it has the advantage of being open source. This basically means that not only the application but also the source code is available to the public.

PhotoRec can work with OS X, Linux, Free BSD, Net BSD, Open BSD, and Windows. It can recover the most common file formats, such as JPEG pictures, MP3 audio files, OpenDocument and Microsoft Office files, PDF documents and ZIP archives. Files can be recovered from different devices such as digital camera memory cards, USB flash drives and hard disks.

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Free Features:

This free file recovery Mac app uses a powerful technology known as file carving. This method consists of two steps. Firstly, it searches for the data block or cluster size. If the file system is not corrupted, this value is obtained from the superblock (ext2/ext3/ext4) or volume boot record (FAT, NTFS). If this is not possible, the app checks each sector of the device, and using the first ten files found, it calculates the block or cluster size.

Secondly, the app reads the device, block by block/cluster by cluster, checking against the different file signatures available in the app’s database, thus assembling and recuperating the available files. Though it’s unclear how many of those file signatures are known to the app.

Overall, it is a nice tool to use when in need to recover some personal files, without having to resort to a professional application.

3. EaseUS Data Recovery Wizard for Mac

EaseUS Data Recovery Wizard is another one of the best data recovery Mac software applications. The developer has released three different versions: free, Pro and unlimited.

Free Features:

The free version is limited to a maximum of 2GB of restored data. This free data recovery software can recover data from Mac notebooks, desktops, hard drives, USB drives, SD cards, memory cards, digital cameras, etc. It works on internal HFS+ drives, and on FAT/FAT32 file systems used in USB flash drives and external hard drives connected to an Apple computer.

Easeus tool recovers file formats most commonly used in image, video, music and document files. It is mostly designed for recovering lost files due to unintentional deletes or drive formatting.

Summarizing, EaseUs free data recovery tool is a handy app designed for casual unintentional file deletions.

4. Softtote Mac Data Recovery

Softtote’s app can recover lost files from internal and external hard drives. File types include ONLY .bmp, .jpg, .png, .tif and .mp3. It works on devices supported by NTFS, HFS/HFS+ and FAT file systems. The application has the capacity to preview file details, such as image size and creation date before recovering them.

Just like other apps in this list, this free data recovery software Mac comes with free technical support.

In brief, Softtote’s software can be included among the best data recovery software Mac, and even though it is not so well known, it deserves a try in case of accidental file loss, but mind the limited set of supported file types.

5. MiniTool Power Data Recovery

MiniTool can recover photos, music, videos, emails, documents, and other types of data from Mac computers or other common storage devices. The free version only offers support via email.

This data recovery software for Mac works in four different modes. The first, “Undelete Recovery”, can be used to quickly recover data lost due to accidental deletion. The second, “Damaged Partition Recovery”, recovers lost data from existing partitions. The third, “Lost Partition Recovery”, recovers lost data from lost or deleted partitions, subject to success in finding them. And finally, the “Digital Media Recovery” mode, recovers multimedia files from portable storage devices.

Free Features:

This data recovery Mac software has a personal edition that is free for use only on one computer and with a maximum restore capacity of 100MB. Is that why it’s called a Mini Tool? Possibly. The developer also offers commercial, enterprise and technician editions of the software.

Overall, MiniTool offers a valid option for the casual accidental delete, in cases that don’t involve big volumes.

The Bottom Line?

We recommend going with Disk Drill, as it delivers on its data recovery odds. This awesome data recovery tool is backed up by good looks, a more intuitive user interface and a ton of free disk tools that may become handy for any user.

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