What does First Aid do on Mac?

First Aid is an important utility included in the macOS operating system that allows users to diagnose and repair issues with their computer’s disk drive. Its purpose is to verify and repair problems with the file system and disk permissions, clear disk caches, rebuild services and permissions, and overall keep a Mac running smoothly.

In this article, we will provide an overview of the various features and functions of First Aid on Mac. We will cover how to use First Aid to verify and repair disk issues, fix permissions, rebuild files and caches, and reset permissions. Understanding what First Aid does and how to properly utilize it can help keep your Mac healthy and optimized for performance.

Verify and Repair Disk

First Aid’s “Verify Disk” function scans the drive and checks for errors and problems with the disk structure. It verifies the HFS directory and volume bitmaps file for inconsistencies. According to iBoysoft, First Aid can detect and repair directory issues, permissions problems, disk structures, bad blocks, journaling issues, and more.

If First Aid detects any errors that can be fixed, it will prompt you to run the “Repair Disk” function. Repair Disk attempts to fix the issues found during the verify process. It can resolve disk corruption issues, directory damage, permission problems, and other disk errors. However, Repair Disk cannot fix hardware problems or recover lost files. Overall, running First Aid regularly can detect and prevent major file system problems.

Fix Permissions

File permissions on Mac determine what actions a user can perform on files and folders. They control read, write, and execute access. Permissions errors can occur if your Mac is unable to correctly set permissions on files, resulting in access issues. This often happens after installing new software or updates.

First Aid’s Fix Permissions tool reviews permissions across your Mac’s system files and user files, identifying any errors. It then repairs the errors, restoring the correct file access permissions. This prevents issues launching apps, editing files, emptying the trash, and more that can result from permissions errors. Overall, Fix Permissions ensures proper file access across your Mac.

According to [1] fixing permissions with First Aid is recommended after major system updates, installation of new apps, or if you experience general system issues. In most cases, it can automatically repair any incorrect file permissions.

[1] https://www.easeus.com/computer-instruction/run-firstaid-from-recovery-mac.html

Rebuild Catalog File

The Catalog File records the locations of all files and folders stored on your Mac’s drive. Over time this file can become corrupted or damaged, causing files and folders to appear missing even when they still exist on the drive. Rebuilding the Catalog File scans the entire drive and recreates this file from scratch, often restoring missing files and folders in the process.

According to experts, rebuilding the Catalog File should be one of the first steps when troubleshooting missing files or folders on a Mac. The process can take 15 minutes or longer depending on the drive size, but is one of the easiest ways to restore missing data. Some even recommend rebuilding the Catalog File once a year as part of regular Mac maintenance to ensure maximum performance.

To rebuild the Catalog File, open Disk Utility and select the drive causing issues. Click “First Aid” then choose the “Rebuild” option next to Catalog File. Let the process run to completion, then restart your Mac. In many cases, previously missing files and folders will reappear after rebuilding the Catalog File.

Source: https://www.easeus.com/knowledge-center/mac-first-aid.html

Repair Disk Permissions

First Aid on Mac has the ability to repair disk permissions. This is different from the separate “Repair Disk” function. Repairing disk permissions fixes the file and folder access permissions on your startup drive to ensure proper read, write, and execute permissions. This can prevent some software errors and system crashes. According to the Mac First Aid article on Practical Help for Your Digital Life, repairing disk permissions checks “the permissions settings for all files on the startup disk and repairs any permissions that are incorrect.”

In contrast, the “Repair Disk” function checks the physical structure of the drive and repairs any directory damage, cross-linked files, catalog file damage, etc. Repairing disk permissions focuses solely on fixing the software access permissions, not physical drive errors. Both functions are useful maintenance tools to optimize your Mac’s performance. Running Repair Permissions ensures proper software functioning, while Repair Disk checks the physical integrity of the drive itself.

Clear System Cache

Clearing the system cache can help speed up your Mac and resolve certain issues by removing unnecessary files that build up over time. The system cache contains temporary files used by apps and system processes to store data for quicker access. However, cache files can become outdated or corrupted.

To clear the system cache on Mac, go to the Apple menu and choose Restart. When you see the Apple logo, immediately press and hold the Option and Command keys. Keep holding until you see the Recovery menu. From there, select Disk Utility and click Continue. In Disk Utility, choose your startup disk and click the First Aid tab. Click “Verify Disk” to check for errors. If errors are found, click “Repair Disk.” This will clear the cache.

Clearing the cache removes unneeded files and frees up valuable disk space. It can fix random performance issues or app crashes related to outdated cache files. After clearing the cache, your Mac should feel faster and more responsive. However, it won’t delete your personal files or settings. Overall, periodically clearing cache is an essential Mac maintenance task to optimize performance.

Reset Home Directory Permissions

A user’s home directory on a Mac contains important configuration files and settings that control how various apps and system features behave for that user. The system applies certain permissions to these files and folders to control what level of access the user has.

Over time, these permissions can become corrupted or set incorrectly, which can cause apps and features to misbehave or fail entirely. Resetting the permissions on the home directory will restore the proper access controls.

To reset home directory permissions on Mac:[1]

  • Open System Preferences and go to Users & Groups
  • Select your user account and click the Reset button under “Reset home directory permissions and ACLs”
  • Restart your Mac

This will recursively reset the ownership and permissions on all files and folders in your home folder to their proper defaults. Doing this periodically can fix odd application issues caused by corrupt permissions.

[1] https://discussions.apple.com/thread/252416429

Rebuild Launch Services

Launch Services is a database on macOS that keeps track of which apps and files are associated with which document types. It helps launch the correct app when you double click a file. Over time, issues can accumulate in this database causing apps to not open files properly.

Rebuilding the Launch Services database clears out these issues and recreates the associations from scratch. This can fix problems with apps failing to open documents they are supposed to handle. Rebuilding Launch Services essentially resets the system’s knowledge of which apps open which files.

To rebuild the Launch Services database on Mac, you can use the following steps:

  1. Open Terminal
  2. Enter the command:
    /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain system -domain user
  3. Restart your Mac

After restarting, Launch Services will be completely rebuilt. Any issues with apps failing to open files should be resolved.

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Additional Features

Beyond repairs and troubleshooting, First Aid on Mac has some other handy capabilities worth mentioning.

One useful feature is the ability to clear the System Management Controller (SMC) information to reset various hardware and power functions. This can help resolve issues like battery problems, fans running constantly, or keyboard/trackpad behaving oddly. To clear SMC info, shut down your Mac, then press and hold the left shift, control and option keys and the power button simultaneously. After 10 seconds, release all keys and power up normally. This will clear out any old SMC data and start fresh [1].

Additionally, First Aid allows you to easily erase and reformat a drive if needed. This can be handy for wiping a disk clean before selling it or repurposing it. Just use the Erase feature and select a format like Mac OS Extended Journaled. This will completely wipe the drive and restore to factory default [2].

So in summary, beyond just repairs, First Aid provides useful maintenance utilities like resetting SMC and reformatting disks as needed. This adds to its versatility as an all-in-one disk health tool.

Conclusion

In summary, First Aid on Mac is an integral tool for diagnosing and fixing issues with your Mac’s disk and file system. By verifying and repairing disks, fixing permissions, rebuilding files, clearing caches and more, First Aid helps keep your Mac running smoothly and avoid serious problems. Its ability to detect and resolve errors makes it an essential utility that every Mac user should be familiar with. Through regular use of First Aid for preventative maintenance, you can proactively ensure your Mac continues operating at peak performance. The simple interface and automated tools of First Aid make it accessible for all users. With First Aid, Mac users have an invaluable resource to optimize system files, recover from crashes, and maintain the health of their computer.

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