Vnc server linux suse

Vnc server linux suse

FigureВ 10.2: Remmina’s Main Window #

The main application window shows the list of stored remote sessions. Here you can add and save a new remote session, quick-start a new session without saving it, start a previously saved session, or set Remmina’s global preferences.

10.2.3 Adding Remote Sessions #Edit source

To add and save a new remote session, click in the top left of the main window. The Remote Desktop Preference window opens.

FigureВ 10.3: Remote Desktop Preference #

Complete the fields that specify your newly added remote session profile. The most important are:

Name of the profile. It will be listed in the main window.

The protocol to use when connecting to the remote session, for example VNC.

The IP or DNS address and display number of the remote server.

User name, Password

Credentials to use for remote authentication. Leave empty for no authentication.

Color depth, Quality

Select the best options according to your connection speed and quality.

Select the Advanced tab to enter more specific settings.

Tip: Disable Encryption

If the communication between the client and the remote server is not encrypted, activate Disable encryption , otherwise the connection fails.

Select the SSH tab for advanced SSH tunneling and authentication options.

Confirm with Save . Your new profile will be listed in the main window.

10.2.4 Starting Remote Sessions #Edit source

You can either start a previously saved session, or quick-start a remote session without saving the connection details.

10.2.4.1 Quick-starting Remote Sessions #Edit source

To start a remote session quickly without adding and saving connection details, use the drop-down box and text box at the top of the main window.

FigureВ 10.4: Quick-starting #

Select the communication protocol from the drop-down box, for example ‘VNC’, then enter the VNC server DNS or IP address followed by a colon and a display number, and confirm with Enter .

10.2.4.2 Opening Saved Remote Sessions #Edit source

To open a specific remote session, double-click it from the list of sessions.

10.2.4.3 Remote Sessions Window #Edit source

Remote sessions are opened in tabs of a separate window. Each tab hosts one session. The toolbar on the left of the window helps you manage the windows/sessions, such as toggle fullscreen mode, resize the window to match the display size of the session, send specific keystrokes to the session, take screenshots of the session, or set the image quality.

FigureВ 10.5: Remmina Viewing Remote Session #

10.2.5 Editing, Copying, and Deleting Saved Sessions #Edit source

To edit a saved remote session, right-click its name in Remmina’s main window and select Edit . Refer to SectionВ 10.2.3, “Adding Remote Sessions” for the description of the relevant fields.

To copy a saved remote session, right-click its name in Remmina’s main window and select Copy . In the Remote Desktop Preference window, change the name of the profile, optionally adjust relevant options, and confirm with Save .

To Delete a saved remote session, right-click its name in Remmina’s main window and select Delete . Confirm with Yes in the next dialog.

10.2.6 Running Remote Sessions from the Command Line #Edit source

If you need to open a remote session from the command line or from a batch file without first opening the main application window, use the following syntax:

Remmina’s profile files are stored in the .local/share/remmina/ directory in your home directory. To determine which profile file belongs to the session you want to open, run Remmina, click the session name in the main window, and read the path to the profile file in the window’s status line at the bottom.

FigureВ 10.6: Reading Path to the Profile File #

While Remmina is not running, you can rename the profile file to a more reasonable file name, such as sle15.remmina . You can even copy the profile file to your custom directory and run it using the remmina -c command from there.

10.3 Configuring One-time Sessions on the VNC Server #Edit source

A one-time session is initiated by the remote client. It starts a graphical login screen on the server. This way you can choose the user which starts the session and, if supported by the login manager, the desktop environment. When you terminate the client connection to such a VNC session, all applications started within that session will be terminated, too. One-time VNC sessions cannot be shared, but it is possible to have multiple sessions on a single host at the same time.

ProcedureВ 10.1: Enabling One-time VNC Sessions #

Start YaST  › Network Services  › Remote Administration (VNC) .

Check Allow Remote Administration Without Session Management .

Activate Enable access using a web browser if you plan to access the VNC session in a Web browser window.

If necessary, also check Open Port in Firewall (for example, when your network interface is configured to be in the External Zone). If you have more than one network interface, restrict opening the firewall ports to a specific interface via Firewall Details .

Confirm your settings with Next .

In case not all needed packages are available yet, you need to approve the installation of missing packages.

Tip: Restart the Display Manager

YaST makes changes to the display manager settings. You need to log out of your current graphical session and restart the display manager for the changes to take effect.

FigureВ 10.7: Remote Administration #

10.3.1 Available Configurations #Edit source

The default configuration on SUSE Linux Enterprise Server serves sessions with a resolution of 1024×768 pixels at a color depth of 16-bit. The sessions are available on ports 5901 for “ regular ” VNC viewers (equivalent to VNC display 1 ) and on port 5801 for Web browsers.

Other configurations can be made available on different ports , see Section 10.3.3, “Configuring One-time VNC Sessions” .

VNC display numbers and X display numbers are independent in one-time sessions. A VNC display number is manually assigned to every configuration that the server supports (:1 in the example above). Whenever a VNC session is initiated with one of the configurations, it automatically gets a free X display number.

By default, both the VNC client and server try to communicate securely via a self-signed SSL certificate, which is generated after installation. You can either use the default one, or replace it with your own. When using the self-signed certificate, you need to confirm its signature before the first connection—both in the VNC viewer and the Web browser.

10.3.2 Initiating a One-time VNC Session #Edit source

To connect to a one-time VNC session, a VNC viewer must be installed, see also Section 10.1, “The vncviewer Client”. Alternatively use a JavaScript-capable Web browser to view the VNC session by entering the following URL: http://jupiter.example.com:5801

10.3.3 Configuring One-time VNC Sessions #Edit source

You can skip this section, if you do not need or want to modify the default configuration.

One-time VNC sessions are started via the systemd socket xvnc.socket . By default it offers six configuration blocks: three for VNC viewers ( vnc1 to vnc3 ), and three serving a JavaScript client ( vnchttpd1 to vnchttpd3 ). By default only vnc1 and vnchttpd1 are active.

To activate the VNC server socket at boot time, run the following command:

To start the socket immediately, run:

The Xvnc server can be configured via the server_args option. For a list of options, see Xvnc —help .

When adding custom configurations, make sure they are not using ports that are already in use by other configurations, other services, or existing persistent VNC sessions on the same host.

Activate configuration changes by entering the following command:

Important: Firewall and VNC Ports

When activating Remote Administration as described in Procedure 10.1, “Enabling One-time VNC Sessions”, the ports 5801 and 5901 are opened in the firewall. If the network interface serving the VNC sessions is protected by a firewall, you need to manually open the respective ports when activating additional ports for VNC sessions. See Chapter 24, Masquerading and Firewalls for instructions.

10.4 Configuring Persistent VNC Server Sessions #Edit source

A persistent session can be accessed from multiple clients simultaneously. This is ideal for demonstration purposes where one client has full access and all other clients have view-only access. Another use case are trainings where the trainer might need access to the trainee’s desktop.

Tip: Connecting to a Persistent VNC Session

To connect to a persistent VNC session, a VNC viewer must be installed. Refer to Section 10.1, “The vncviewer Client” for more details. Alternatively use a JavaScript-capable Web browser to view the VNC session by entering the following URL: http://jupiter.example.com:5801

There are two types of persistent VNC sessions:

10.4.1 VNC Session Initiated Using vncserver #Edit source

This type of persistent VNC session is initiated on the server. The session and all applications started in this session run regardless of client connections until the session is terminated. Access to persistent sessions is protected by two possible types of passwords:

a regular password that grants full access or

an optional view-only password that grants a non-interactive (view-only) access.

A session can have multiple client connections of both kinds at once.

ProcedureВ 10.2: Starting a Persistent VNC Session using vncserver #

Open a shell and make sure you are logged in as the user that should own the VNC session.

If the network interface serving the VNC sessions is protected by a firewall, you need to manually open the port used by your session in the firewall. If starting multiple sessions you may alternatively open a range of ports. See ChapterВ 24, Masquerading and Firewalls for details on how to configure the firewall.

vncserver uses the ports 5901 for display :1 , 5902 for display :2 , and so on. For persistent sessions, the VNC display and the X display usually have the same number.

To start a session with a resolution of 1024×768 pixel and with a color depth of 16-bit, enter the following command:

The vncserver command picks an unused display number when none is given and prints its choice. See man 1 vncserver for more options.

When running vncserver for the first time, it asks for a password for full access to the session. If needed, you can also provide a password for view-only access to the session.

The password(s) you are providing here are also used for future sessions started by the same user. They can be changed with the vncpasswd command.

Important: Security Considerations

Make sure to use strong passwords of significant length (eight or more characters). Do not share these passwords.

To terminate the session shut down the desktop environment that runs inside the VNC session from the VNC viewer as you would shut it down if it was a regular local X session.

If you prefer to manually terminate a session, open a shell on the VNC server and make sure you are logged in as the user that owns the VNC session you want to terminate. Run the following command to terminate the session that runs on display :1 : vncserver -kill :1

10.4.1.1 Configuring Persistent VNC Sessions #Edit source

Persistent VNC sessions can be configured by editing $HOME/.vnc/xstartup . By default this shell script starts the same GUI/window manager it was started from. In SUSE Linux Enterprise Server this will either be GNOME or IceWM. If you want to start your session with a window manager of your choice, set the variable WINDOWMANAGER :

Note: One Configuration for Each User

Persistent VNC sessions are configured in a single per-user configuration. Multiple sessions started by the same user will all use the same start-up and password files.

10.4.2 VNC Session Initiated Using vncmanager #Edit source

ProcedureВ 10.3: Enabling Persistent VNC Sessions #

Start YaST  › Network Services  › Remote Administration (VNC) .

Activate Allow Remote Administration With Session Management .

Activate Enable access using a web browser if you plan to access the VNC session in a Web browser window.

If necessary, also check Open Port in Firewall (for example, when your network interface is configured to be in the External Zone). If you have more than one network interface, restrict opening the firewall ports to a specific interface via Firewall Details .

Confirm your settings with Next .

In case not all needed packages are available yet, you need to approve the installation of missing packages.

Tip: Restart the Display Manager

YaST makes changes to the display manager settings. You need to log out of your current graphical session and restart the display manager for the changes to take effect.

10.4.2.1 Configuring Persistent VNC Sessions #Edit source

After you enable the VNC session management as described in ProcedureВ 10.3, “Enabling Persistent VNC Sessions”, you can normally connect to the remote session with your favorite VNC viewer, such as vncviewer or Remmina. You will be presented with the login screen. After you log in, the ‘VNC’ icon will appear in the system tray of your desktop environment. Click the icon to open the VNC Session window. If it does not appear or if your desktop environment does not support icons in the system tray, run vncmanager-controller manually.

FigureВ 10.8: VNC Session Settings #

There are several settings that influence the VNC session’s behavior:

This is equivalent to a one-time session. It is not visible to others and will be terminated after you disconnect from it. Refer to Section 10.3, “Configuring One-time Sessions on the VNC Server” for more information.

The session is visible to other users and keeps running even after you disconnect from it.

Here you can specify the name of the persistent session so that it is easily identified when reconnecting.

No password required

The session will be freely accessible without having to log in under user credentials.

Require user login

You need to log in with a valid user name and password to access the session. Lists the valid user names in the Allowed users text box.

Allow one client at a time

Prevents multiple users from joining the session at the same time.

Allow multiple clients at a time

Allows multiple users to join the persistent session at the same time. Useful for remote presentations or trainings.

Confirm with OK .

10.4.2.2 Joining Persistent VNC Sessions #Edit source

After you set up a persistent VNC session as described in Section 10.4.2.1, “Configuring Persistent VNC Sessions”, you can join it with your VNC viewer. After your VNC client connects to the server, you will be prompted to choose whether you want to create a new session, or join the existing one:

FigureВ 10.9: Joining a Persistent VNC Session #

After you click the name of the existing session, you may be asked for login credentials, depending on the persistent session settings.

10.5 Configuring Encryption on the VNC Server #Edit source

If the VNC server is set up properly, all communication between the VNC server and the client is encrypted. The authentication happens at the beginning of the session; the actual data transfer only begins afterward.

Whether for a one-time or a persistent VNC session, security options are configured via the -securitytypes parameter of the /usr/bin/Xvnc command located on the server_args line. The -securitytypes parameter selects both authentication method and encryption. It has the following options:

Authentications #

VncAuth, TLSVnc, X509Vnc

Authentication using custom password.

Plain, TLSPlain, X509Plain

Authentication using PAM to verify user’s password.

Encryptions #

TLSNone, TLSVnc, TLSPlain

Anonymous TLS encryption. Everything is encrypted, but there is no verification of the remote host. So you are protected against passive attackers, but not against man-in-the-middle attackers.

X509None, X509Vnc, X509Plain

TLS encryption with certificate. If you use a self-signed certificate, you will be asked to verify it on the first connection. On subsequent connections you will be warned only if the certificate changed. So you are protected against everything except man-in-the-middle on the first connection (similar to typical SSH usage). If you use a certificate signed by a certificate authority matching the machine name, then you get full security (similar to typical HTTPS usage).

Tip: Path to Certificate and Key

With X509 based encryption, you need to specify the path to the X509 certificate and the key with -X509Cert and -X509Key options.

If you select multiple security types separated by comma, the first one supported and allowed by both client and server will be used. That way you can configure opportunistic encryption on the server. This is useful if you need to support VNC clients that do not support encryption.

On the client, you can also specify the allowed security types to prevent a downgrade attack if you are connecting to a server which you know has encryption enabled (although our vncviewer will warn you with the «Connection not encrypted!» message in that case).

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