“Could not mount” (com.apple.DiskManagement.disenter error 0, 49153, 49218): what to do

What you’re seeing

The full message looks like: Could not mount “Untitled”. (com.apple.DiskManagement.disenter error 49153.) You get it from Disk Utility’s Mount button or from diskutil mount. The numbers seen most often are 0, 49153 and 49218. I couldn’t find an official Apple document that defines them, so the explanations below come from patterns in user reports, not from Apple. Treat them as likely, not certain.

• The volume is busy. After an unclean eject macOS often runs a file system check in the background. Mounting during that check fails.
• The file system is damaged or dirty (APFS, HFS+, exFAT or FAT).
• macOS can’t mount that format for example a drive with a partition macOS doesn’t recognise.
• The drive or its connection is failing, so reads time out.

Gentle steps, in order

1. Eject, wait, reconnect. Use a different cable and port, directly on the Mac. Give it a minute or two. In Activity Monitor, search for “fsck”: if a check is running, let it finish.
2. Restart the Mac with the drive disconnected, then connect it. A restart clears a stuck disk-arbitration state, and some users report that it was the only thing that cleared the error.
3. Check the Mac can see the device. In Disk Utility choose View > Show All Devices. In Terminal run diskutil list (read-only) and note the identifier, such as disk4s2.
4. Try mounting read-only: diskutil mount readOnly disk4s2. Mounting read-only doesn’t modify the volume, so if it works you can copy files out in Finder straight away. If it works, copy everything now.
5. Ask macOS to verify without fixing: diskutil verifyVolume disk4s2 reads the volume and reports problems. It doesn’t repair. A clean result with a mount failure suggests a connection or hardware issue; errors point at the file system.
6. Only then consider First Aid. Apple’s steps are to run First Aid on the volume, then the container, then the device (Apple). First Aid writes to the drive. If it fails with exit code 8, see Disk Utility First Aid failed (exit code 8).

On macOS 15 Sequoia and macOS 26 Tahoe the steps are the same. If the drive doesn’t appear in diskutil list at all, the error isn’t your problem; see External hard drive not showing up on Mac.

Copy your files off with Retrova

Retrova doesn’t ask macOS to mount the volume, so the disenter error doesn’t apply to it. It reads the volume directly, read-only, and understands APFS, Mac OS Extended (HFS+), exFAT, FAT, NTFS, ext4, XFS and Btrfs.

1. Plug the drive in and open Retrova. On the home screen choose A drive won’t open. Retrova lists every drive and partition it can see, with the file system it detected.
2. Pick the drive or partition. macOS asks for your administrator password at this point, because reading a disk directly needs it. Retrova only uses it to read.
3. Browse and choose what you want back. If the file system is readable you see your original folders and file names, and you can preview photos, videos, PDFs and text before copying.
4. Choose a destination on a different drive with enough free space. Retrova never saves onto the drive it is reading.
5. Copy, then Verify. Files are written as temporary parts and renamed only when complete. When it finishes, run Verify to compare every copy with the original, byte for byte.

If no file system is recognised, or the one it finds is too damaged to list files, run Deep scan from I deleted something. Deep scan ignores the file system and searches the raw drive for the start of 72 known file types (photos including camera RAW, videos, audio, documents, archives, mail files and more). It only recovers files that were stored in one piece, and the original names and folders are lost: finds come back sorted by type with new names.

For an APFS volume specifically, see Recover files from an APFS drive that macOS won’t mount. If the volume is encrypted (FileVault-style encrypted APFS), Retrova marks it Locked and opens it when you enter the password. You can also unlock it in macOS first (diskutil apfs unlockVolume disk4s2) and copy files from Finder. The startup disk of a T2 or Apple silicon Mac can’t be opened away from that Mac.

What Retrova can’t do: it can’t undelete files with their names on APFS, ext or other file systems (only NTFS, FAT and exFAT), can’t open an encrypted drive without its password or recovery key, can’t open the startup disk of a T2 or Apple silicon Mac away from that Mac, doesn’t handle RAID sets or phones, and can’t fix a drive with physical damage. Retrova’s builds aren’t signed or notarised yet, so macOS and Windows will show a warning the first time you open it.

What not to do

Questions

Sources

• Apple: Repair a Mac storage device with Disk Utility

Related guides

• Disk Utility First Aid failed (exit code 8)What the error means and what to do before you try again.
• External drive not mounting on a Mac? Get your files off it firstmacOS sees the drive but it will not open? The safe order of things.
• Recover files from an APFS drive that macOS won’t mountFirst Aid failed and the volume stays greyed out? Read the APFS structures directly.
• External drive not mounting on macOS TahoePermission, Finder and Disk Utility checks, then a safe copy.