Disk permissions on macOS are a critical aspect of the file system that determine who can read, write, or execute files. These permissions are designed to protect the integrity of the system and user data. When a hard drive is set to “Read Only,” it means that the user can view files but cannot modify, delete, or add new ones.
This setting is often applied to external drives or partitions for security reasons, but it can also occur due to improper mounting or file system errors.
MacOS uses a Unix-based file system, which relies on permission flags to manage access. These flags include Read (r), Write (w), and Execute (x). When a drive is in “Read Only” mode, the Write permission is disabled. To change this, you need to modify the file system settings or remount the drive with the correct permissions.
Using Disk Utility to Modify Permissions
Disk Utility is a built-in macOS tool that allows you to manage and repair disks, partitions, and volumes. It provides a graphical interface for modifying disk permissions, making it an accessible option for users who prefer not to use the command line.
To change the “Read Only” permission using Disk Utility:
- Open Disk Utility from the Applications > Utilities folder.
- Select the hard drive or partition that is set to “Read Only” from the sidebar.
- Click on the First Aid button to check for and repair any file system errors.
- If the drive is still in “Read Only” mode, click the Mount button to remount it with write permissions.
If Disk Utility fails to resolve the issue, you may need to use Terminal to manually adjust the permissions.
Using Terminal Commands to Change Permissions
Terminal is a powerful command-line interface that allows you to execute advanced commands on macOS. It is particularly useful for modifying file system settings that are not accessible through graphical tools like Disk Utility.
To change the “Read Only” permission using Terminal:
- Open Terminal from the Applications > Utilities folder.
- Type
diskutil listand press Enter to display all connected drives and partitions. - Identify the disk identifier (e.g.,
/dev/disk2s1) for the “Read Only” drive. - Unmount the drive by typing
sudo diskutil unmount /dev/disk2s1and pressing Enter. - Remount the drive with write permissions using the command
sudo mount -uw /dev/disk2s1.
This process ensures that the drive is remounted with the correct permissions, allowing you to modify its contents.
Common Causes of “Read Only” Mode
Several factors can cause a hard drive to enter “Read Only” mode. Understanding these causes can help you prevent the issue in the future.
One common cause is improper ejection of external drives. If a drive is disconnected without being properly ejected, macOS may remount it in “Read Only” mode to prevent data corruption. Another cause is file system errors, which can occur due to power outages, hardware failures, or software bugs. Additionally, drives formatted with certain file systems, such as NTFS, may default to “Read Only” mode on macOS unless specific drivers are installed.
Preventing Future Permission Issues
To avoid encountering “Read Only” mode in the future, follow these best practices:
- Always eject external drives properly before disconnecting them.
- Regularly check and repair file system errors using Disk Utility.
- Format drives with macOS-compatible file systems, such as APFS or HFS+, when possible.
- Keep your macOS system and software up to date to avoid bugs and compatibility issues.