Written by
Amanda Wong
Summary: If you can't mount the drive on your Mac and receive the error mount failed with 77, you can find the solutions in this post. To troubleshoot the mount failed with 77 issue without data loss, you can try iBoysoft Data Recovery for Mac to recover data from an unmountable drive.
It is frustrating to find the drive unmountable on a Mac, which means all the drive data is inaccessible. When the drive is not automatically mounted on the Mac, you can manually mount it via the Mount button in Disk Utility. If it doesn't work, you can try to mount the drive via Terminal. Besides, you may need to mount the volume/drive in Terminal to perform some tasks, however, it returns the "mount: / failed with 77" error.
Hello! Recently, I have been trying to use Single User Mode and have run into a problem. When I try to mount / as read/write, I get "operation not permitted," and "mount: / failed with 77." I have used the command said in the booting process, "To Mount the root filesystem as read/write, do /sbin/mount -X /" but that has not worked either. Why might this be? Thanks in advance!
If you encounter the same mount failed with 77 error on your Mac, keep reading to get the fixes!
Recover drive data when drive mount failed with 77
When the "mount: / failed with 77" error occurs, it also makes the drive data inaccessible. If you want to access all your files/folders stored on the unmountable drive, you will need third-party data recovery software. Professional data recovery for Mac such as iBoysoft Data Recovery for Mac can scan the problematic drive, show the scanned results, and enable you to recover all/certain items.
iBoysoft Data Recovery for Mac fully supports the latest macOS Sequoia and is compatible with both Intel Macs and Apple Silicon Macs. It can help save your data in a variety of situations, including unbootable Mac recovery, SSD/HDD/SD card/USB recovery, Mac startup disk recovery, etc.
Here's how to recover data from drive mount failed with 77:
- Free download, install, and launch the iBoysoft Data Recovery for Mac.
- Connect the external drive that returns the mount failed with 77 error.
- Select Storage Device from the left sidebar and choose the unmountable drive from the right list.
- Click the Search for Lost Data button to start scanning the selected drive.
- Wait for the process to complete. Filter files by different categories and preview them.
- Check the boxes of the items you want to recover and tap the Recover button to save them to a different location.
Recommend iBoysoft Data Recovery for Mac to help others recover data!
How to fix the mount failed 77 error on Mac?
If you have already recovered the drive data, you can proceed to fix the mount failed 77 issue on your external hard drive so that you can mount and use the drive as normal.
Fix 1. Check the connection
When the external hard drive performs abnormally on your Mac, the connection could be the culprit, you should make sure the USB port, USB cable, and the USB hub(if you are using one), are working. You can follow the steps below to check the connection issue:
- Disconnect the external disk from your Mac.
- Look for any obvious debris or damage in the USB port.
- If you are using a USB hub, try to connect the disk directly to your Mac.
- Insert the drive into a different USB cable, ideally one that is known to function.
- Replug the drive into the USB port firmly.
- With the drive connected, check if it mounts successfully. If not, move to the next fix.
Fix 2. Disable SIP
On macOS, System Integrity Protection (SIP) can sometimes interfere with mounting operations, particularly for external devices or network shares. If SIP is blocking the operation, you may encounter the mount failed with 77 error. By default, SIP is enabled, you can follow the steps below to turn it off:
- Completely shut down the Mac, and boot into macOS Recovery Mode.
- Open Terminal from the Utilities menu.
- Type the command below and press Enter: csrutil disable
- Quit Terminal and restart your Mac.
Fix 3. Force mount the drive via Terminal
If the Mount feature of Disk Utility doesn't work, Terminal offers another way with certain command lines to mount external hard drives on Mac. Files that might be interfering with your external hard drive's normal mounting can be removed with these commands. Make sure you have already saved the drive data and run the correct commands here:
- Connect the external drive to your Mac.
- Launch Terminal from the Applications folder > Utilities.
- Enter the command line below and press Enter: diskutil list
- Examine the list of all devices to find the external disk that is not mounting.
- Input the following command and replace usb with the name of your unmountable disk: sudo mkdir /Volume/usb
- Type the following command and replace disk1 with the disk identifier of your drive: sudo mount -t hfs /dev/disk1 /Volume/usb
- Quit Terminal and check whether the external hard disk shows up on the Mac desktop or in Finder.
Fix 4. Erase the drive
Unluckily, the above methods don't work to fix the mount failed with 77 error on your external hard drive, then you can try to format the external hard drive on Mac to eliminate logical errors on it, this may fix the unmountable drive and bring it back on track.
By the way, the process will delete all drive data, if there is no backup, you should first use data recovery software such as iBoysoft Data Recovery for Mac to save your important files.
- Connect the drive to your Mac's USB port.
- Open Disk Utility from the Launchpad.
- Select the external drive that can not be mounted and click Erase.
- Give the disk a name and select a macOS-compatible file system.
- Click Erase, then eject the disk and reconnect it again to check whether it mounts successfully.
Let others know how to fix the mount failed with 77 error!
