Frequently Asked Questions / Troubleshooting¶

Uninstalling Scyld FlexLM on Windows fails to remove application¶

Microsoft provides a tool that can help automatically repair issues that prevent existing applications from being uninstalled. See the following URL for more information:

https://support.microsoft.com/en-us/topic/fix-problems-that-block-programs-from-being-installed-or-removed-cca7d1b6-65a9-3d98-426b-e9f927e1eb4d

Firefox Snap 113 on Ubuntu 22 can’t launch Scyld Cloud Workstation Client when opening `scw://` URIs.¶

This is a known issue with the Firefox Snap package. Install and connect with Chrome to workaround this issue.

Why do I get stuck on the loading page when I sign in with Safari?¶

If the server is using a self-signed certificate, then Safari will refuse the necessary websocket connections from the server. You may also see a message in the Javascript Console that says:

WebSocket network error: OSStatus Error -9807: Invalid certificate chain

There are a few workarounds:

The most secure option is to contact your system administrator about either using a trusted certificate for the server.
Add the server’s self-signed certificate to your Keychain Access. NOTE: This is not recommended if the server is using the certificate that is included with Scyld Cloud Workstation.
The simplest and least secure workaround is to use a different browser such as Chrome or Scyld Cloud Workstation Client.

Are there any known conflicts with anti-virus software?¶

Enabling Avast Antivirus can crash or cause unstable with the native client. Possible workarounds include creating an exception for the native client or disabling Avast.

Why does pasting into a MacOS terminal result in “^[[200~” being displayed?¶

Certain terminal-based programs (such as zsh shell) come with a feature called “bracketed paste mode”. Bracketed paste mode will wrap your pasted string with a ^[[200~ and ~ so that the program can distinguish pasted text from directly typed text.

Please consult the documentation for these terminal-based programs for more information on bracketed paste mode.

Why is USB Forwarding disabled after updating MacOS Big Sur (or earlier) to MacOS Monterey (or later)?¶

When Scyld Cloud Workstation is installed on versions of MacOS older than Monterey, it deploys the ‘VirtualHere’ application to support USB Forwarding. Monterey will not run this application, however, so it must be replaced with ‘VirtualHereUniversal’ to re-enable USB Forwarding.

Please see: Re-Enabling USB Forwarding after Updating to MacOS Monterey for installation instructions.

Why do I see two cursors for MacOS with only one user signed in?¶

There are two reasons this might occur:

When Wacom tablets are connected, we intentionally draw the mouse cursor to make stylus navigation easier.
MacOS servers that do not have a physical display or display dongle attached will always draw the remote cursor. Installing a display dongle or a physical display should resolve this issue.

Why is video performance poor in Chrome, Firefox, or Edge?¶

Hardware acceleration for WebGL can be blocked for certain graphics cards and driver combinations in Microsoft Edge, Google Chrome, and Mozilla Firefox browsers.

Follow the browser specific steps below to determine if your browser is blocking WebGL hardware acceleration and force the browser to enable it. If you continue to have trouble getting WebGL hardware acceleration to work after following the steps below you may need to:

Update your driver (Intel, AMD, or NVIDIA)
Switch to a compatible browser
Switch to Scyld Cloud Workstation Client (Recommended!)

Important

Forcing WebGL hardware acceleration may cause the browser to be unstable. If you are unsure about any of this, please download and install the native client as a workaround instead!

Forcing WebGL in Google Chrome¶

Open Chrome and go to URL chrome://gpu
Under Graphics Feature Status, look for the lines starting with WebGL: and WebGL2:
If those values are NOT: Hardware accelerated, then your browser is likely blocking WebGL hardware acceleration.
If you suspect WebGL hardware acceleration is blocked, you can try forcing this feature by following these steps:
1. Go to URL chrome://flags/#ignore-gpu-blocklist
2. Use the dropdown to set its value to Enabled.
3. Restart the browser by clicking on the Relaunch button.

Forcing WebGL in Mozilla Firefox¶

Open Firefox and go to URL about:support
Scroll down to the Graphics section.
In the WebGL 1 Driver Renderer section, you may see a message about it being Blocked for your graphics card.
If you suspect WebGL hardware acceleration is blocked, you can try forcing this feature by following these steps:
1. Go to URL about:config
2. A warning page may appear. Click I accept the risk! to go to the about:config page.
3. Search for webgl.force-enabled and set the value to true by double-clicking on the row.
4. Search for layers.acceleration.force-enabled and set the value to true by double-clicking on the row.
5. Restart Firefox to apply your new settings.

Forcing WebGL in Microsoft Edge¶

Open Microsoft Edge and go to URL edge://gpu
Under Graphics Feature Status, look for the lines starting with WebGL: and WebGL2:
If those values are NOT: Hardware accelerated, then your browser is likely blocking WebGL hardware acceleration.
If you suspect WebGL hardware acceleration is blocked, you can try forcing this feature by following these steps:
1. Go to edge://flags/#ignore-gpu-denylist
2. Use the dropdown to set its value to Enabled.
3. Restart the browser by clicking on the Restart button.

Why does my MacOS display not go to sleep?¶

Scyld Cloud Workstation prevents Display Sleep from happening in MacOS using an application called caffeinate. This is to prevent the computer from going to sleep, which would make Scyld Cloud Workstation inaccessible.

How do I use reserved keyboard shortcuts such as Command-Space?¶

Command-Space is a common keyboard shortcut in MacOS used to access Spotlight. This can conflict with the CentOS 7 equivalent keyboard combination of Super-Space, which is used to a change of the keyboard layout.

Currently the only workaround that will let you transmit Command-Space and a few other keyboard shortcuts reserved by the OS is to disable the keyboard shortcut locally.

Starting the service in Linux results in “X11 connection rejected because of wrong authentication.”¶

The message indicates there’s an X permissions issue. This may be due to a missing X11 magic cookie in your user’s $HOME/.Xauthority file.

To add the missing X11 magic cookie value, first determine the display number used by linuxuser:

linuxuser@host:~$ echo $DISPLAY
host:21.0

In this example it is 21.0. Next, display linuxuser’s list of cookies:

linuxuser@host:~$ xauth list
host/unix:1  MIT-MAGIC-COOKIE-1  51a3801fd7776704575752f09015c61d
host/unix:21  MIT-MAGIC-COOKIE-1  0ba2913f8d9df0ee9eda295cad7b1010
host/unix:22  MIT-MAGIC-COOKIE-1  33cd4803819fca0ef8297dba308ceeee

The cookie for the 21.0 display is the second in the list.

Next, log in as root and add this particular cookie to the root’s .Xauthority file with the xauth command:

root@host:~$ xauth add host/unix:21 MIT-MAGIC-COOKIE-1 0ba2913f8d9df0ee9eda295cad7b1010

Finally, try restarting X and check if Scyld Cloud Workstation is running.

My image is very pixelated. How do I improve image quality?¶

Increasing the Server.Video.AvgBitRate values will improve image quality at the cost of higher bandwidth. For example, if you want to increase the average bit rate at 1080p to 10 Mbps and you have sufficient bandwidth on the server and client side, we recommend setting Server.Video.AvgBitRate to the following:

1280x720=5000k,1920x1080=10000k

You may want to experiment for your particular use case. Setting this value too high may render the system slow or unusable for servers and clients with poor bandwidth.

My desktop is flickering between a dark gray screen and my desktop!¶

This is a known issue with older versions of Firefox (such as 52.4.0) and has been observed in CentOS 7. Please update to 60.8 or whatever the latest available version of Firefox.

When I fullscreen the remote desktop in Firefox my screen is cropped!¶

As a workaround, first exit fullscreen. Now try using the Firefox menu to zoom out until the entire remote desktop window fits and then use the fullscreen option.

How do I create non-standard resolutions in Windows with an NVIDIA GPU?¶

It is important to use the NVIDA Control Panel to change to a non-standard resolution. Using the Windows Display Manager will result in a corrupt desktop image.

Why does Google Chrome 61-62 show inaccurate colors?¶

Newer versions of Google Chrome (Chrome 61 and 62) use the ICC profile provided by the local OS rather than forcing its own color profile. This may make the colors appear different from what you may see in other browsers or in the Native Client.

As a workaround you can enter chrome://flags/#force-color-profile in your Chrome URL bar and select sRGB from the dropwdown. Then close and restart Chrome.

Can LDAP credentials be used at the sign in page?¶

Yes. There are two ways to support this.

Traditionally support for LDAP currently comes as part of the Scyld-Cloud-Manager package. Scyld Cloud Workstation can be configured to authenticate through Scyld-Cloud-Auth, which can talk to LDAP. To connect to a Scyld-Cloud-Auth service, open the config file, set Server.Auth.ScyldCloudAuth.URL, and add one or more Username elements to the Server.Auth.ScyldCloudAuth.Allow.

As of v6.1.0, Scyld Cloud Workstation passes credentials directly to the remote operating system. This feature is enabled by default, but it can be disabled by setting Server.Auth.OSAuthEnabled to false.

I’m only seeing a gray rectangle.¶

This is either caused by caching problems in the browser, an unsupported screen resolution, or an unexpected error between the client and server.

Try signing out, opening a new web browser, and trying again. If the problem persists, check the web browser’s JavaScript Console and the Scyld Cloud Workstation log file (Linux: /var/log/messages) for errors.

If the JavaScript Console shows an error message containing net::ERR_CERT_AUTHORITY_INVALID in Chrome, you may want to try Firefox or reset Chrome to its original factory settings.

If you are a CentOS user, verify that Xorg is running on DISPLAY :0 by running ps aux | grep X. If you do not see a line that looks like Xorg :0, you may need to restart X by running init 3 and init 5 in CentOS.

How do I press Ctrl+Alt+Del or Print Screen?¶

There is a shortcut button for this keyboard combination in the Keyboard Menu in the top control bar.

How do I press Ctrl+N, Ctrl+T, Ctrl+W, Ctrl+Tab, Ctrl+Page Up, or Ctrl+Page Down?¶

This is typically when web browsers reserve these keyboard shortcuts. One workaround is to install the latest version of our native client, Scyld Cloud Workstation Client. Chrome users can try another workaround, described below.

By default, Google Chrome (aka Chromium) intercepts certain specific keyboard combinations before Scyld Cloud Workstation can receive them. There is a special “app mode” available for Chrome users that can be activated at the command line by appending the --app=<url> flag. For example:

google-chrome --app=https://host/

This will open a borderless Chrome browser that will relay many of these key combinations to Scyld Cloud Workstation. If this is something you will do often, we recommend creating a shortcut with a flag to your Scyld Cloud Workstation host.

Note

Certain keyboard combinations, such as Ctrl+Alt+Del and Alt+Tab are intercepted by the client operating system and are not relayed to the Scyld Cloud Workstation interface.

What ports do I need to open?¶

By default, Scyld Cloud Workstation must be able to accept incoming requests over HTTPS port 443 (or port 80 if you are using HTTP).

Can I run my applications?¶

Scyld Cloud Workstation is completely unaware of what applications are being run on the remote operating system. In other words, if your application can run directly on the remote host, it can be displayed on Scyld Cloud Workstation.

Will it run on my iPad / mobile device?¶

We do not yet officially support iPad or mobile devices, but we have had some success getting view-only functionality to work with an iPhone SE.

Is there audio support?¶

Yes. As of v10.0 we support dual channel audio.

Can I cut, copy, and paste?¶

You can copy text from the local desktop to the remote desktop. See Paste Text from the Local Clipboard for more information.

What graphics cards do you support?¶

See Server Hardware.

How many NVIDIA GRID GPUs do I need?¶

As of v5.0, NVIDIA GRID GPUs are no longer required to run Scyld Cloud Workstation.

What Xorg.conf options do I need for an NVIDIA GRID / Tesla card over GPU passthrough?¶

First, find the appropriate BusID for your graphics card using the following command:

nvidia-xconfig --query-gpu-info | awk '/PCI BusID/{print $4}'

PCI:27:1:0

The BusID in this example is PCI:27:1:0. (Note: other tools such as lspci show the bus ID in a hexadecimal format that must be manually converted to decimal format).

For older NVIDIA GRID cards (K1 or K2) add the BusID and the “UseDisplayDevice” “none” option. Modify the Xorg.conf file so that the Device and Screen sections look similar to the following:

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BusID          "PCI:27:01:0"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "UseDisplayDevice" "none"
    SubSection     "Display"
        Virtual     1440 900
        Depth       24
    EndSubSection
EndSection

For NVIDIA Tesla M60 users add the BusID (note: the syntax below is also valid). You may also want to specify a DPI (as needed) if images on the screen appear too wide or narrow. Modify the Xorg.conf file so that the Device section looks similar to the following:

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "Tesla M60"
    BusID          "PCI:27:01:0"
    Option         "DPI" "96x96"
EndSection