Known Issues

Performance Considerations

To reduce the number of requests to the remote server for mounted volumes, we recommend the following settings when running in Online connect mode.

  • Choose View → Hide Preview (⌘⇧P)

  • Disable View → Show View Options → Show icon preview

Temporary Files

When opening files with status Online only or when connected with Online connect mode, it may be required to temporarily cache contents depending on the read pattern of the application opening the file. Data is stored in the temporary file location of the operating system and allows for faster access when repeatedly reading the file. Temporary files are deleted as soon as the application closes the file after reading, unless the option Enable buffering checked in Preferences → Sync.


When enabled Preferences → Sync → Enable buffering is enabled:

  • In Online connect mode, buffered content in temporary files is kept until disconnecting the bookmark.

  • In Smart Synchronization connect mode, the buffer contents is moved from the temporary folder to the local cache and the status of the file changes to Up to Date.


Files and Folders not Synced from Server

Files matching the following naming pattern are excluded from folder listings and not synchronized from the server. These characters are reserved for the operating system or file system and can’t be used to name files or directories.

  • : (colon)

  • / (forward slash)

  • \ (backslash)

Files and Folders not Uploaded to Server

Files and folders matching temporary filename patterns are excluded from sync by default. This includes .DS_Store,*~$, *~.*, ._~$*, *.tmp, ~*.tmp, *~*.TMP, *.swap, *.swp, .TemporaryItems, .dat.nosync*, DBTmp*, *.lck, *.idlk, Desktop.ini, Thumbs.db, *.crdownload, *.part

New Files and Folders

New empty (0-byte) files created in Windows Explorer using New → … are not transferred to the server. New folders created in or Windows Explorer not renamed are not uploaded to the server. Change the folder name to something else than Untitled Folder on macOS or New Folder on Windows to synchronize to the server.

In Untitled folder and localized variants created using File → New Folder

Known Issues

Download trial failed. Error

This is a known bug appearing from time to time while downloading the trial version of Mountain Duck. Please reach out to the Mountain Duck support to receive a trial license file.

Not a valid registration key Error

This error appears if you try to use a license key for older versions of Mountain Duck for a new major version. Registration keys are valid for the current major version at the time of purchase and for previous versions. To use the latest major version you will have to upgrade your license. Alternatively, install an older version of Mountain Duck from the changelog.

Interoperability with Adobe Acrobat

There are known bugs when using Adobe Acrobat Reader to work with files from network drives:

  • Can only open single PDF files.

  • Cannot export files as JPG files.

As a workaround uncheck edit → Preferences… → Security (Enhanced) → Enable Protected Mode at startup.

rsync Fails with Error

If your server does not accept the creation of . temporary files you might need to add the --inplace when running rsync.

High CPU usage when working with Sublime Text

  • When working with Sublime Text we recommend turning off indexing by adding the following setting to your user preferences in Sublime Text.
    "index_files": false

  • You might want to turn off Git support in Sublime which has caused high CPU usage for some users when scanning .git folders.
    "show_git_status": false

Sharing a Mounted Drive in Local Network

It is not possible to share a mounted drive within the local network.

Changes from Server not Immediately Visible

The directory listing in on macOS or File Explorer on Windows may become out of date when another application is adding, removing, or modifying files on the server. No push notifications are received for changes on the server. The following strategies are in place to detect changes to existing and new files as soon as possible:

  • Periodically polls for changes for open folders in Finder or File Explorer about every minute in both Online and Smart Synchronization connect modes.

  • With Preferences → Sync → Index Files enabled, folders previously opened are polled for changes and new files in Smart Synchronization connect mode.

  • Immediately look for changes from the server when opening a new folder in on macOS or File Explorer on Windows.


You can explicitly request to look for changes on the server in a folder by choosing Reload from the context menu.

Cache Uses a lot of Disk Space

Disk space is used on your computer for every cached file marked as Up to Date or In Sync in Smart Synchronization connect mode. Files are cached as soon as accessed (e.g. open in any application or previewing in on macOS or File Explorer on Windows) or explicitly with Keep Offline on Local Disk.

The cache size can be limited per bookmark in Preferences → Sync. Also files not accessed within a chosen period of time can be purged. Refer to Cache Limitations.

The cache directory is located in %LocalAppData%\Cyberduck\Cache on Windows or within Application Support folder on macOS by default. You can change the cache location to any writable location. You can clear cached files from the local disk with the Delete on local disk context menu option.

Send Command

Insufficient Disk Space

If the available disk space on the mounted volume is below 100MB a soft quota notification will be displayed saying Insufficient space. Synchronization is paused when the soft quota is reached.

Soft Quota Insufficient disk space

This quota information is only available for the following protocols:

View Files from Synology Drive

Synology Drive is not supported natively. You can try to view your Synology Drive files by connecting to your Synology NAS. To do that connect to your Synology NAS using the protocol SFTP, FTP, or WebDAV with the path home/Drive.


This won’t allow you to view and access shared files and folders.

Graphical Artifacts with VLC player

Playing video files from a mounted drive using VLC player can cause graphical artifacts and video corruption when pausing and resuming the playback. As a workaround, increase the caching time in VLC → Preferences → Show All → Input/Codecs → Scroll down to Advanced → set File Caching (ms).

Missing Sync Status Icons

When you have other applications installed that register a Finder Extension (macOS) for the volume mounted, the status icon may not appear. This has been reported for the following applications:

Please check in System Preferences → Extension → Finder for other applications that may override the badge icons. For macOS Ventura and later, the setting can be found in System Settings → Privacy & Security → Extensions → Added Extensions.


If none of those applications are in use, a Finder re-launch can make the badge icons appear again.

Operating System Specific Issues

Missing status bar icon
Using applications customizing the status menus may lead to a missing status icon of Mountain Duck. This has been reported for the following applications:

  • xbar

  • MenuMeters

  • IP in menubar

Mount is not Visible within the Media Browser (Adobe Premiere)
Bookmarks mounted by Mountain Duck aren’t visible within the Media Browser of Adobe Premiere. The mount location needs to be changed (e.g. to the desktop) to make the mount visible. Does not Show Files Prefixed with . on Remote Volumes
You can work around this by setting defaults write AppleShowAllFiles YES in a window and restart using → Force Quit … → Finder → Relaunch. If you are running macOS Sierra (10.12) you can choose ⌘⇧. to toggle files starting with a dot to show in

Original Document can’t be Changed (
Files opened in and edited cannot be saved at the original location but the message “The original document can’t be changed, so a duplicate with your changes has been created” is displayed in the title bar. As a workaround, you can set a custom mount point in Preferences → Connection → Mount Location for volumes such as a ~/Volumes/ folder in your home directory.

Enable Application Icon in Dock
As a utility application with no application windows, no icon is displayed in the Dock but only in the system status bar. If you want to enable the application icon to appear in the Dock set the following property:

defaults write io.mountainduck application.dock.icon.enable true

Mounted Volumes do not Appear on the Desktop
Navigate to volumes using ⌘⇧C in a window or choose Finder → Preferences … → General → Show these items on the desktop: Connected Servers to make the volume appear on the desktop. Mounted volumes are also listed in the sidebar in Favorites.

Search in (Spotlight)
The Spotlight search does not work on remote volumes.

Spotlight Indexer
To prevent the indexing through Spotlight the default mount location has been changed to Volumes.noindex. In case you do want the mount location to be indexed by Spotlight, use the command mdutil -i on <mount location>. Additionally, mount location to a directory without the extension .noindex.


Enabling Spotlight can cause high CPU and bandwidth usage while indexing folders.

Multiple Mountain Duck Finder Extensions Processes
The system may launch additional copies of Mountain Duck Finder Extension whenever an Open or Save dialog is displayed. This means there may be multiple copies of the extension running at once, and some may be very short-lived.

Connection Interrupted
It may be that Finder closes the connection because Mountain Duck hasn’t answered fast enough on the request of Finder. Although Finder indicates that the server connection is interrupted it isn’t as Mountain Duck is still connected to the server.

This is an issue within the operating system that can occur to any network drive.

Extended Attributes
Extended attributes containing metadata about the files some applications write in addition to the file content are saved in auxiliary ._* files. These are only saved in a temporary location and not synchronized. If you want to save ._* files to the server set the hidden configuration option:

defaults write io.mountainduck fs.filenames.metadata.enable false


Hosting Service Providers

A list of known providers that fail to work with Mountain Duck due to interoperability issues.

  • OwnCube: Their deployment does not work and we discourage this product.

  • Bitnami ownCloud: PHP-FPM is enabled by default in virtual machines and Ubuntu-based cloud images but must be disabled for uploads to complete. Refer to How to disable PHP-FPM and 0 byte files on WebDAV server.

Third-Party Software

Kaspersky Internet Security

Make sure to uninstall Kaspersky Internet Security with its kernel extensions causing kernel panics prior to mounting a volume.

Eset Cyber Security Pro

Make sure not connections on the loopback interface are blocked.


Be aware that Bitdefender may interfere with connections.

Sophos Endpoint Protection

May interfere with installation.


Time Machine
Backups to Time Machine do not work with volumes mounted from Mountain Duck. Time Machine requires disks mounted using Apple File Protocol (AFP). See Backup disks you can use with Time Machine.

Bug Reports and Feature Requests

To get help with bugs, feature requests, or other issues please refer to support.