X0VNCSERVER(1)

NAME
x0vncserver - TigerVNC Server for X displays

SYNOPSIS
x0vncserver [options]
x0vncserver -version

DESCRIPTION
x0vncserver is a TigerVNC Server which makes any X display remotely accessible via VNC, TigerVNC or compatible viewers. Unlike Xvnc(1), it does not create a virtual display. Instead, it just shares an existing X server (typically, that one connected to the physical screen). XDamage will be used if the existing X server supports it. Otherwise x0vncserver will fall back to polling the screen for changes.

OPTIONS
x0vncserver interprets the command line as a list of parameters with optional values. Running x0vncserver -h will show a list of all valid parameters with short descriptions. All parameters are optional, but normally you would have to use the PasswordFile parameter (see its description below).

There are several forms of specifying parameters in the command line (here we use `SomeParameter' as an example parameter name):

-SomeParameter
    Enable the parameter, turn the feature on. This form can be used with parameters that simply enable or disable some feature.

-SomeParameter=0
    Disable the parameter, turn the feature off.

-SomeParameter=value
    Assign the specified value to the parameter. The leading dash can be omitted, or it can be doubled if desired (like in GNU-style long options).

Parameter names are case-insensitive, their order in the command line can be arbitrary.

PARAMETERS

-desktop desktop-name
    Each desktop has a name which may be displayed by the viewer. It defaults to "<user>@<hostname>".

-display display
    The X display name. If not specified, it defaults to the value of the DISPLAY environment variable.

-rfbport port
    Specifies the TCP port on which x0vncserver listens for connections from viewers (the protocol used in VNC is called RFB - "remote framebuffer"). Specify -1 to disable listening on a TCP port. The default port is 5900 when started directly, and -1 when activated by a systemd socket.

-UseIPv4
    Use IPv4 for incoming and outgoing connections. Default is on.

-UseIPv6
    Use IPv6 for incoming and outgoing connections. Default is on.

-rfbunixpath path
    Specifies the path of a Unix domain socket on which x0vncserver listens for connections from viewers. Default is to not listen to any Unix domain socket.

-rfbunixmode mode
    Specifies the mode of the Unix domain socket. The default is 0600.

-Log logname:dest:level
    Configures the debug log settings. dest can currently be stderr, stdout or syslog, and level is between 0 and 100, 100 meaning most verbose output. logname is usually * meaning all, but you can target a specific source file if you know the name of its "LogWriter". Default is *:stderr:30.

-HostsFile filename
    This parameter allows to specify a file name with IP access control rules. The file should include one rule per line, and the rule format is one of the following: +address/prefix (accept connections from the specified address group), -address/prefix (reject connections) or ?address/prefix (query the local user). The first rule matching the IP address determines the action to be performed. Rules that include only an action sign (+, - or ?) will match any IP address. Prefix is optional and is specified as a number of bits (e.g. /24). Default is to accept connections from any IP address.

-SecurityTypes sec-types
    Specify which security scheme to use for incoming connections. Valid values are a comma separated list of None, VncAuth, Plain, TLSNone, TLSVnc, TLSPlain, X509None, X509Vnc, X509Plain, RA2, RA2ne, RA2_256 and RA2ne_256. Default is TLSVnc,VncAuth.

-rfbauth passwd-file, -PasswordFile passwd-file
    Password file for VNC authentication. There is no default, you should specify the password file explicitly. Password file should be created with the vncpasswd(1) utility. The file is accessed each time a connection comes in, so it can be changed on the fly.

-Password password
    Obfuscated binary encoding of the password which clients must supply to access the server. Using this parameter is insecure, use PasswordFile parameter instead.

-PlainUsers user-list
    A comma separated list of user names that are allowed to authenticate via any of the "Plain" security types (Plain, TLSPlain, etc.). Specify * to allow any user to authenticate using this security type. Specify %u to allow the user of the server process. Default is to deny all users.

-pam_service name, -PAMService name
    PAM service name to use when authentication users using any of the "Plain" security types. Default is vnc.

-X509Cert path
    Path to a X509 certificate in PEM format to be used for all X509 based security types (X509None, X509Vnc, etc.).

-X509Key path
    Private key counter part to the certificate given in X509Cert. Must also be in PEM format.

-GnuTLSPriority priority
    GnuTLS priority string that controls the TLS session’s handshake algorithms. See the GnuTLS manual for possible values. Default is NORMAL.

-RSAKey path
    Path to the RSA key for the RSA-AES security types (RA2, RA2ne, RA2_256 and RA2ne_256) in PEM format.

-RequireUsername
    Require username for the RSA-AES security types. Default is off.

-UseBlacklist
    Temporarily reject connections from a host if it repeatedly fails to authenticate. Default is on.

-BlacklistThreshold count
    The number of unauthenticated connection attempts allowed from any individual host before that host is black-listed. Default is 5.

-BlacklistTimeout seconds
    The initial timeout applied when a host is first black-listed. The host cannot re-attempt a connection until the timeout expires. Default is 10.

-QueryConnect
    Prompts the user of the desktop to explicitly accept or reject incoming connections. Default is off.

-QueryConnectTimeout seconds
    Number of seconds to show the Accept Connection dialog before rejecting the connection. Default is 10.

-localhost
    Only allow connections from the same machine. Useful if you use SSH and want to stop non-SSH connections from any other hosts.

-interface IP address
    Listen on interface. By default x0vncserver listens on all available interfaces.

-AlwaysShared
    Always treat incoming connections as shared, regardless of the client-specified setting. Default is off.

-NeverShared
    Never treat incoming connections as shared, regardless of the client-specified setting. Default is off.

-DisconnectClients
    Disconnect existing clients if an incoming connection is non-shared. Default is on. If DisconnectClients is false, then a new non-shared connection will be refused while there is a client active. When combined with NeverShared this means only one client is allowed at a time.

-AcceptKeyEvents
    Accept key press and release events from clients. Default is on.

-AcceptPointerEvents
    Accept pointer movement and button events from clients. Default is on.

-AcceptSetDesktopSize
    Accept requests to resize the size of the desktop. Default is on.

-RemapKeys mapping
    Sets up a keyboard mapping. mapping is a comma-separated string of character mappings, each of the form char->char, or char<>char, where char is a hexadecimal keysym. For example, to exchange the " and @ symbols you would specify the following:
    RemapKeys=0x22<>0x40

-RawKeyboard
    Send keyboard events straight through and avoid mapping them to the current keyboard layout. This effectively makes the keyboard behave according to the layout configured on the server instead of the layout configured on the client. Default is off.

-Protocol3.3
    Always use protocol version 3.3 for backwards compatibility with badly-behaved clients. Default is off.

-Geometry geometry
    This option specifies the screen area that will be shown to VNC clients. The format is widthxheight+xoffset+yoffset , where `+' signs can be replaced with `-' signs to specify offsets from the right and/or from the bottom of the screen. Offsets are optional, +0+0 is assumed by default (top left corner). If the argument is empty, full screen is shown to VNC clients (this is the default).

-MaxProcessorUsage percent
    Maximum percentage of CPU time to be consumed when polling the screen. Default is 35.

-PollingCycle milliseconds
    Milliseconds per one polling cycle. Actual interval may be dynamically adjusted to satisfy MaxProcessorUsage setting. Default is 30.

-FrameRate fps
    The maximum number of updates per second sent to each client. If the screen updates any faster then those changes will be aggregated and sent in a single update to the client. Note that this only controls the maximum rate and a client may get a lower rate when resources are limited. Default is 60.

-CompareFB mode
    Perform pixel comparison on framebuffer to reduce unnecessary updates. Can be either 0 (off), 1 (always) or 2 (auto). Default is 2.

-UseSHM
    Use MIT-SHM extension if available. Using that extension accelerates reading the screen. Default is on.

-ImprovedHextile
    Use improved compression algorithm for Hextile encoding which achieves better compression ratios by the cost of using slightly more CPU time. Default is on.

-IdleTimeout seconds
    The number of seconds after which an idle VNC connection will be dropped. Default is 0, which means that idle connections will never be dropped.

-MaxDisconnectionTime seconds
    Terminate when no client has been connected for N seconds. Default is 0.

-MaxConnectionTime seconds
    Terminate when a client has been connected for N seconds. Default is 0.

-MaxIdleTime seconds
    Terminate after N seconds of user inactivity. Default is 0.

SEE ALSO
Xvnc(1), vncpasswd(1),
https://www.tigervnc.org/

AUTHOR
Constantin Kaplinsky and others. VNC was originally developed by the RealVNC team while at Olivetti Research Ltd / AT&T Laboratories Cambridge. TightVNC additions were implemented by Constantin Kaplinsky. Many other people have since participated in development, testing and support. This manual is part of the TigerVNC software suite.