Virtual Desktop

On UCloud, users can run web-based desktop applications. These software applications are installed within a virtual desktop environment (VDE) based on a Linux distribution such as AlmaLinux and Ubuntu. Examples of software applications with a graphical user interfaces (GUIs) deployed in a VDE include: ANSYS, COMSOL, MATLAB.

Note

In some of the VDE apps the software GUI launches upon startup, and closing the GUI also terminates the job.

To launch a VDE app, users should follow the same procedure outlined in the previous section for interactive apps. However, upon clicking the button labeled

a remote desktop opens inside a pop-up window, which can be resized as needed.

Below are additional features of VDE apps.

Web Browsers

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Firefox and Chrome web browsers provide direct access to the internet.

Remote Filesystem

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The remote filesystem of the application container can be browsed via the Linux file manager. If data folders are mounted from UCloud, they will be visible within the /work directory, which serves as the default working tree of the application.

Important

Please note that only new files and folders created within the default working tree will be saved after the job completion.

Terminal Window

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Access to a shell window is provided by the Terminal application on the desktop.

The startup directory for the terminal is always /work. The default user inside the application container is ucloud, which also has superuser account privileges. Therefore, full read, write, and execute permissions are enabled using sudo in front of any command, without the need to enter an administrator password.

Before installing a new software, it is recommended to update the system libraries. For this purpose, run the command:

$ sudo yum update

or

$ sudo dnf update

for a AlmaLinux-based app, and

$ sudo apt-get update

in case of an Ubuntu-based app.

Display Resolution

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The method for changing the resolution depends on whether the VDE uses KDE or Xfce. Run the commands below in a terminal inside the virtual desktop.

KDE (Wayland)

The KDE VDE uses Wayland with labwc. Its resolution adjusts to the browser window by default. To keep a fixed resolution, open the noVNC sidebar, select Settings, and change Scaling Mode from Remote Resizing to Local Scaling or None.

List the display outputs and their current resolutions:

$ wlr-randr

For example, to set a screen of 2560x1440 pixels at 60 Hz, run:

$ wlr-randr --output HEADLESS-1 --custom-mode 2560x1440@60Hz

Use the output name reported by wlr-randr if it differs from HEADLESS-1.

Xfce (X11)

The Xfce desktop resolution can be adjusted using the Display application accessible from the virtual desktop.

To list the display outputs and available resolutions, run:

$ xrandr

The examples below use VNC-0; replace it with the output name reported by xrandr if different.

Custom display resolutions can be added via the terminal window. For example, to set a screen of 2560x1440 pixels at 60 Hz, first execute the command:

$ cvt 2560 1440 60

Tip

# 2560x1440 59.96 Hz (CVT 3.69M9) hsync: 89.52 kHz; pclk: 312.25 MHz

Modeline "2560x1440_60.00" 312.25 2560 2752 3024 3488 1440 1443 1448 1493 -hsync +vsync

then, create the new display mode using the second line in the output, as shown below:

$ xrandr --newmode "2560x1440_60.00"  312.25  2560 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync

and

$ xrandr --addmode VNC-0 2560x1440_60.00

The new resolution can be selected directly from the Display application or via command line:

$ xrandr --output VNC-0 --mode 2560x1440_60.00