Problem with mounting in directory without drive letter

Just recently I have installed Cryptomator 1.5.1 (exe-166) on Windows 10.
Dokany version is “Dokan Library 1.3.0.1000 (x64)”
I could not find anything on the problem here, so I am asking for help.
By the way, I have encountered the problem on two different computers.

I do not want to mount using a drive letter. Instead, the decrypted directory is in my file system, say C:\mnt\a. I am using Dokany (no WebDAV). Everything worked fine so far. However, when I tried to mount the vault the next day, I got an error. I am adding the error log below.

The key to the problem seems to be the error “Cannot assign a drive letter or mount point. Probably already used by another volume.” This is funny, since the empty folder C:\mnt\a still exists. Even deleting C:\mnt\a and recreating it does not help at all.

However:
The problem can be solved by creating and mounting to a new folder C:\mnt\b. With this, I can mount without problems.

This might be a Dokany problem. Maybe an unclean dismount?

Here is the error log with the seemingly most relevant information close to the end:

org.cryptomator.common.vaults.Volume$VolumeException: Unable to mount Filesystem
	at org.cryptomator.common.vaults.DokanyVolume.mount(DokanyVolume.java:57)
	at org.cryptomator.common.vaults.Vault.unlock(Vault.java:118)
	at org.cryptomator.ui.common.VaultService$UnlockVaultTask.call(VaultService.java:299)
	at org.cryptomator.ui.common.VaultService$UnlockVaultTask.call(VaultService.java:278)
	at javafx.concurrent.Task$TaskCallable.call(Task.java:1425)
	at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)
Caused by: org.cryptomator.frontend.dokany.MountFailedException: java.lang.IllegalStateException: Mount failed: Cannot assign a drive letter or mount point. Probably already used by another volume.
	at org.cryptomator.frontend.dokany.MountFactory.mount(MountFactory.java:128)
	at org.cryptomator.common.vaults.DokanyVolume.mount(DokanyVolume.java:52)
	... 8 more
Caused by: java.lang.IllegalStateException: Mount failed: Cannot assign a drive letter or mount point. Probably already used by another volume.
	at com.dokany.java.DokanyDriver.start(DokanyDriver.java:72)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
	... 4 more

Hello to the Community :slight_smile: ,

Yes. This is a known bug scheduled for an upcoming 1.5.x release. Another user already opened a ticket for this on our issue tracker, see

Thanks. Although in my Case the errror message is a little different, it might have the same reason.

So I will wait and test it again with a later version.

Thanks for your help!

Ah sorry, i oversaw this sentence. We also have a similar bug report (this time with exact the same error message), where one user could solved it by changing the permissions to access the directory.

Thanks a lot.

Next time I get the error I will try changing the permissions.

I have the same problem with the newest software.
Just installed newest Cryptomator 1.5.8 and Dokany 1.4.0. My system is Windows 10 Home with all the updates.

Create vault in OneDrive: Work1ODVault.
Then attempt to choose new empty OneDrive folder ‘ODVault’ as mountpoint.

Unexpected error occurred:

org.cryptomator.common.vaults.Volume$VolumeException: Unable to mount Filesystem
	at org.cryptomator.common.vaults.DokanyVolume.mount(DokanyVolume.java:57)
	at org.cryptomator.common.vaults.Vault.unlock(Vault.java:129)
	at org.cryptomator.ui.unlock.UnlockWorkflow.attemptUnlock(UnlockWorkflow.java:103)
	at org.cryptomator.ui.unlock.UnlockWorkflow.call(UnlockWorkflow.java:80)
	at org.cryptomator.ui.unlock.UnlockWorkflow.call(UnlockWorkflow.java:43)
	at javafx.concurrent.Task$TaskCallable.call(Task.java:1425)
	at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
	at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)
Caused by: org.cryptomator.frontend.dokany.MountFailedException: java.lang.IllegalStateException: Mount failed: Cannot assign a drive letter or mount point. Probably already used by another volume.
	at org.cryptomator.frontend.dokany.MountFactory.mount(MountFactory.java:128)
	at org.cryptomator.common.vaults.DokanyVolume.mount(DokanyVolume.java:52)
	... 11 more
Caused by: java.lang.IllegalStateException: Mount failed: Cannot assign a drive letter or mount point. Probably already used by another volume.
	at com.dokany.java.DokanyDriver.start(DokanyDriver.java:72)
	... 5 more

I then tried to select a folder on a ‘normal’ drive as mountpount, that worked, but it defeats my purpose of having both the vault and the link folder together in OneDrive.

A previous answer said it might be fixed by ‘changing the permissions to access the directory’, but doesn’t say which directory and which permissions.

You need to change the permissions of the mountpoint (in your case ODVault) to be writeable.

But your setup is . If you mount the vault inside OneDrive into a folder which is also located in OneDrive, any change will be “double” sync’d, because from the change of the cleartext a sync is made and from the change of the encrypted file a sync is triggered.

Additionally, i am skeptical if OneDrive supports symbolic links/junction points, and that is how a unlocked vault is integrated into the filesystem (i.e. the mountpoint is a symbolic link).

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