Chapter 11. Remotely accessing the desktop as multiple users

You can remotely connect to the desktop on a RHEL server and open multiple sessions as different users at the same time.

Prerequisites

  • Install the VNC server: 

    # dnf install tigervnc-server

  • Install the VNC client: 

    # dnf install tigervnc

11.1. The mapping of port and display numbers to users in VNC

With VNC, the client can connect to the desktop sessions of different users on the server. A display number and a TCP port number are attached to each server user that exports a VNC session. The client uses the port number to specify which server user it connects to.

If several clients connect using the same port number, they all open a VNC session to the same server user.

You must configure a mapping for each server user that exports a VNC session. For every such user, you must pick a unique port and display number.

The recommended mapping

Red Hat recommends that you start with port number 5902 and display number 2 for the first user, and increment the numbers by one for each additional server user.

Port number 5900 and display number 0 represent the server user that is currently logged into the graphical session. You cannot start a VNC server for the user who is already logged into the graphical session.

Table 11.1. Port and display number pairs

Port numberDisplay numberNote

5900

0

The logged-in user

5901

1

 

5902

2

The first recommended VNC user

5903

3

 

…

…

 
Important

Red Hat recommends that you do not configure the root user to export a VNC session. A root VNC session is unsafe and certain elements of the session might not work as expected.

Firewall rules

You must open the selected ports in your firewall configuration. Allowing the vnc-server service in your firewall opens ports from 5900 to 5903. If you need to enable access to additional server users, you must open ports above 5903 by manually specifying the port numbers.

11.2. VNC server configuration files

Several configuration files affect the behavior of the VNC server. You can configure the user mapping and various global options.

General options

You can configure general options of the VNC server in the /etc/tigervnc/vncserver-config-defaults configuration file. The file uses the following format: 

option1=value
option2

For example: 

session=gnome
alwaysshared
securitytypes=vncauth,tlsvnc
desktop=sandbox
geometry=2000x1200

The priority of configuration files

The VNC server reads the following files for general options, in order from most important to least important:

  1. /etc/tigervnc/vncserver-config-mandatory

    This file replaces the default configuration and has a higher priority than the per-user configuration. It is intended for system administrators who want to enforce particular VNC options.

  2. $HOME/.vnc/config

    Individual users can override the default VNC configuration in this file.

  3. /etc/tigervnc/vncserver-config-defaults

    This file stores the default VNC configuration.

User mapping

You can configure the mapping between users and their associated port and display numbers in the /etc/tigervnc/vncserver.users configuration file. The file uses the following format: 

:number=user

For example: 

:2=test
:3=vncuser

Additional resources

  • For a list of available configuration options, see the Xvnc(1) man page.

11.3. Enabling multi-user VNC access on the server

This procedure configures a RHEL server so that multiple users can open VNC sessions on it at the same time.

Prerequisites

  • If you previously configured VNC using systemd unit files, remove any outdated VNC configuration: 

    [root]# rm /etc/systemd/system/vncserver@.service

Procedure

  1. Map users to display and port numbers.

    In the /etc/tigervnc/vncserver.users configuration file, add a line for each server user that will export a VNC session: 

    :user-number=user-name
    • Replace user-number with the port and display number mapped to the selected existing user.
    • Replace user-name with the user name of the selected existing user.

    For example: 

    :2=vncuser

  2. Open TCP ports 5900 to 5903 in the firewall: 

    [root]# firewall-cmd --permanent --add-service=vnc-server

  3. Reload the firewall rules: 

    [root]# firewall-cmd --reload

  4. Add the following lines to the /etc/tigervnc/vncserver-config-defaults configuration file: 

    session=gnome
alwaysshared

    This configuration has the following effects:

    • The VNC server starts the GNOME session when a remote user logs in.
    • Multiple users can connect to the VNC server at the same time.

  5. As each server user that exports a VNC session, set the VNC password for the user: 

    [regular-user]$ vncpasswd

    Remote clients must enter this password when connecting to the desktop on the server.

  6. If you previously configured VNC for the user, ensure that the configuration files have the correct SELinux context: 

    [regular-user]$ restorecon -RFv ~/.vnc

  7. Enable and start the VNC server unit for the regular user: 

    [root]# systemctl enable --now vncserver@:user-number

  8. If the server uses the proprietary Nvidia driver, disable Wayland:

    1. Uncomment the WaylandEnable=False line in the /etc/gdm/custom.conf configuration file.
    2. Add the DefaultSession=gnome-xorg.desktop option to the [daemon] section of the configuration file.
    3. Reboot the server.

Additional resources

11.4. Connecting to the VNC server as multiple users

This procedure connects to a remote desktop session using the vncviewer application. You can open multiple connections to the remote desktop at the same time.

Prerequisites

Procedure

  • Connect to the VNC server: 

    $ vncviewer --shared server-ip:display
    • Replace server-ip with the IP address of the server that you are connecting to.
    • Replace display with the display number where the server user exports the VNC session.