In this section we describe how to start and stop the Scyld Cloud Workstation service in either Linux or Windows on the remote server. We then talk about how to connect and interact with the remote desktop interface.
Using the Linux Service¶
To start, stop, or restart the scyld-cloud-workstation, open a terminal
with root or sudo privileges and use the
service scyld-cloud-workstation start service scyld-cloud-workstation stop service scyld-cloud-workstation restart
To run scyld-cloud-workstation directly rather than as a service (this is
usually only useful for debugging purposes), use the
scyld-cloud-workstation.sh start-up script. Usage information can be
obtained by passing the
usage: scyld-cloud-workstation OPTIONS scyld-cloud-workstation -- a GPU accelerated remote desktop web service. --daemon Run application as a daemon. --pidfile=path Write the process ID of the application to given file. -h, --help display help information on command line arguments -vsvideosource, --videosource=videosource choose videosource (nvfbc, stream) -q, --quiet hide the console when running -pwd, --passwd update the password
Using the Windows Service¶
To use the scyld-cloud-workstation service, we must verify that the service is registered with the OS and then start the service.
Open a Command Prompt as an Administrator¶
- Sign in as a user that is an Administrator.
- Click on the Windows Start menu.
- In the Search box, type
Command Prompt, but don’t hit
- Right-click on the Command Prompt and select
Run as administrator.
Register the Windows Service¶
To register the windows service, use the
scyld-cloud-workstation.exe /registerService /startup=automatic
The scyld-cloud-workstation will now automatically start on reboot.
Service registration should already be handled by the installer. If you the message below, verify that scyld-cloud-workstation has been properly installed. This is usually a sign that the PATH environment variables are not pointing at the scyld-cloud-workstation.exe.
'scyld-cloud-workstation.exe' is not recognized as an internal or external command, operable program or batch file.
Start and Stop the Windows Service¶
To start and stop the registered windows service without rebooting,
net start scyld-cloud-workstation net stop scyld-cloud-workstation
Change the Config File Password¶
Scyld Cloud Workstation lets you optionally store a username and hashed password in the config file for authentication. The credentials specified by Server.Auth.Username and Server.Auth.ShadowPassword attributes are entirely independent from LDAP, the remote operating system, and ScyldCloudAuth.
You can change this password by calling
--passwd in Linux or
scyld-cloud-workstation.exe /passwd in Windows from
a command line. This password change takes effect without a
Password strength requirements are described in the Setup chapter under Server.Auth.ShadowPassword.
This only changes the Server.Auth.ShadowPassword entry in the config file. It does not change the passwords used by the remote operating system, LDAP, or ScyldCloudAuth.
Log output is organized by priority levels (from highest to lowest:
Fatal, Critical, Error, Warning, Notice, Information, Debug, and
Trace). scyld-cloud-workstation by default prints Information level
information will log all server
starts/stops, sign-in attempts, socket connects/disconnects, video
source plays/pauses, and additional warning/error messages. This is
usually sufficient for production usage.
To see debug and higher level output, open the scyld-cloud-workstation.xml
config file and set
In Linux, debug and higher level log messages can be found at:
In Windows, debug and higher level log messages can be found at:
C:\Program Files\Penguin Computing\Scyld Cloud Workstation\log\win-service.log and
C:\Program Files\Penguin Computing\Scyld Cloud Workstation\log\scyld-cloud-workstation.log.
You can change the path of the output by opening the
scyld-cloud-workstation.xml config file and setting
a new destination.
By default, Scyld Cloud Workstation does not display a timestamp with each log
message. To add a timestamp to all of your output, open the
scyld-cloud-workstation.xml and set
%q%q: %s:%u: %t.
Selecting a Video Source¶
Scyld Cloud Workstation currently supports two video sources:
For most users an appropriate default video source will be
automatically detected based on the system’s configuration. Hosts
that have an NVIDIA GRID card with a compatible NVIDIA GRID driver
installed default to
nvfbc. All other systems will default to
To override the video source, specify
Server.VideoSource in the config file.
Once the Scyld Cloud Workstation server has started, users can connect their
networked client to the server by typing the server’s URL into the web
browser. Servers using the HTTPS protocol (default) have
URLs like this:
This will take you to the Scyld Cloud Workstation sign in page. Submit the username and password encrypted in the config file or by ScyldCloudAuth to sign in.
As a third option, you can use your OS specific credentials to sign in.
While config file or ScyldCloutAuth usernames can be used to sign in to Scyld Cloud Workstation at any time, only a single set of OS credentials can only be used to sign-in at a time. This prevents different OS credentials from signing in at the same time.
After signing in you will see a gray canvas that will turn into a remote visualization display within a few seconds. At this point you can interact with the remote operating system. Other users will be prevented from signing into the web service until you sign out.
The control buttons allow you to enter fullscreen mode, submit
Ctrl-Alt-Del to the remote OS, or sign out from Scyld Cloud Workstation
Key-combinations such as
Ctrl+T are not relayed to Scyld Cloud Workstation in most browsers. Chrome
users can work around this issue by running Chrome in “app mode” by
--app=<url> flag when calling it from a command
line or shortcut.
Key-combinations such as
Ctrl-Alt-Del are intercepted by the
client OS and must be sent to Scyld Cloud Workstation via control buttons.
Paste Text from the Local Clipboard¶
Text can be pasted from the local client into the remote desktop.
To paste text from a local Linux / Windows clipboard into the remote
Linux / Windows desktop, press
To paste text from a local OS X clipboard to the remote Linux /
Windows desktop, use your browser’s menu system to select
Paste. This transfers the local clipboard to the remote
clipboard. Once this is done, you can use
Ctrl+V or use your
remote application’s paste feature.
Only characters that are supported by both the client and server can be pasted.
Change Screen Resolution¶
Changing screen resolutions has one known issues:
- Multiple rapid resolution changes may lead to service instability. Changing the screen resolution more than 5 times over a few seconds may cause the service to restart or quit.
In Windows, right click on the desktop and select
resolution. Change the resolution dropdown to your desired
resolution and then click ‘OK’.
In Linux, if you are using a first generation NVIDIA GRID card (i.e.,
K1, K2) in a headless configuration (i.e. you are using the
UseDisplayDevice none option in your
you will have to open a command prompt and use the
<width>x<height> command. For example, if you’d like to change the
screen resolution to 1920x1080, you would enter:
Otherwise change your screen resolution by using the provided Linux OS tools (dependent on distribution).
Downscale Screen Resolution¶
System administrators have the ability to restrict the maximum screen
resolution in the config file at
scyld-cloud-workstation.xml using the
This is useful for preventing clients from being overwhelmed by the
processing power required to work with high-resolution video.
If the user attempts to use a higher screen resolution, the user will get an alert and the video will be scaled down.
Enable 4K Support¶
As of v7.0.0 it is possible to support 4K desktops with the native, non-browser based client. This feature is not enabled by default and requires a configuration file change to disable the default screen size and bitrate caps. We recommend having a downlink of at least 20 Mbps to support the increased screen size.
In future releases 4K support will be enabled automatically.
If you are not going to use 4K resolutions then leave the following settings at their defaults by commenting them out or deleting them from the config file. The default screen size and bitrate caps are used to ensure a good user experience for slower clients.
The following steps enable 4K support:
- Open the xml config file.
- Add the
Server.Video.MaxHeighttags with the value set to
-1to disable the resolution cap.
- Save the config file and restart the service.
NVIDIA GRID products (such as a Tesla M60) require an NVIDIA Quadro Virtual Datacenter Workstation license to use 4K resolutions. Contact NVIDIA for more information.
Video Bit-Rate Selection¶
As of v7.1.0, the default video bit-rate is calculated by using a
linear regression of two values: 2500 kbps at 1280x720 and 5000 kbps
at 1920x1080. A system administrator can customize bit-rates for
different resolutions by adding two or more resolution and bit-rate
pairings within the
Server.Video.AvgBitRate config file setting.
The syntax is as follows:
Example 1: the following is equivalent to the default bit-rate
Example 2: the following can be used to specify a single average
bit-rate setting across all resolutions:
The linear regression algorithm is based on the two closest
resolutions to allow a fine-grained bit-rate control. If the value
only specifies one resolution and bit-rate, the service will use
0x0=128k as one of the two linear regression points.
Windows and Linux users must change users by using the remote OS’s log out / log in feature. Scyld Cloud Workstation does not support “fast user switching” and the service must be restarted if this happens.
Closing your browser or signing out of the Scyld Cloud Workstation session does not sign you out of the remote operating system. Use the remote OS’s signing-out capability to sign out of the remote OS.
Multiple users can now share control of the same desktop. There are two types of users in this case: regular Host users and temporary Guest users.
Hosts are are fully trusted users who have an account on the system and have complete control over what a Guest can access. An ongoing session begins when one Host is signed in and ends when the last Host leaves. All Guests and Invites are removed when an ongoing session ends.
Guests are users who are invited to join an ongoing session. As a Host, this can be useful when you want to share a workstation with a remote colleague who should not have a permanent account on the system.
This section describes how a Host adds and manages Guest users.
The Guest alerts and interface buttons described below are not visible in fullscreen mode.
Set the maximum number of concurrent clients¶
By default the server only allows 6 users to be signed on at any
given time. This number can be changed by a system administrator
by adding a
Server.ConcurrentClients.MaxClientCount setting in
the config file at
Collaboration Quick Start¶
At a high level, adding a new guest involves three steps:
- A Host creates an Invite Link and sends it to Guest users
- A Guest opens the Invite Link, enters a Guest name, and attempts to sign in
- A Host accepts the Guest’s sign in request
Hosts can use the control buttons to pause video to all Guests or ban all Guests and revoke all pending Invites. Hosts can also click on user buttons to kick individual Guests or give keyboard and mouse control.
Add New Guests¶
Hosts can invite a group of guests by creating an Invite Link. Click on the ‘Add Guests’ button.
In the form that appears, specify how many guest sign ins you’d like this link to be good for. It is best practice to select the minimum number you will need.
The next form will show the generated Invite Link. Copy and send this link to Guest users and then close the form.
Anyone who receives an Invite Link can request Guest access to your system. While these links expire over time and are limited by how often they can be used it is best practice to keep this link confidential.
When Guests use this link to request a sign in, an alert will appear to all Hosts asking whehter the user should be Accepted or Declined.
It is best practice to verify the incoming user’s identity via a phone call, text message, or other trusted communication channel.
When a Guest signs in, their username becomes reserved until all Hosts sign out. Guest usernames must be unique and consist of only letters, numbers, and underscores. Once the session ends, all Guest usernames are freed again for use.
Pause Guest Video¶
Guest video can be toggled by clicking on the ‘Pause Guests’ button.
Ban Guests and Revoke Invites¶
Guests can be banned for the session either individually or all at the same time using the ‘Ban Guests’ button. Hosts can not be banned.
Give Keyboard and Mouse Control¶
A Host can give any other user control of the keyboard and mouse using the ‘Give Keyboard and Mouse Control’ button.