sudo cp /etc/gdm/gdm.conf /etc/gdm/gdm.conf.bak
2.2.3. XDCMP Support
Setting this to 1 enables XDMCP support allowing remote displays/X terminals to be managed by GDM.
gdm listens for requests on UDP port 177. See the Port option for more information.
If GDM is compiled to support it, access from remote displays can be controlled using the TCP Wrappers library. The service name is gdm
You should add
to your /etc/hosts.allow. See the hosts_access(5) man page for details.
Please note that XDMCP is not a particularly secure protocol and that it is a good idea to block UDP port 177 on your firewall unless you really need it.
Enables XDMCP INDIRECT choosing (i.e. remote execution of gdmchooser) for X-terminals which don't supply their own display browser.
To avoid denial of service attacks, GDM has fixed size queue of pending connections. Only MaxPending displays can start at the same time.
Please note that this parameter does *not* limit the number of remote displays which can be managed. It only limits the number of displays initiating a connection simultaneously.
GDM will only provide MaxPendingIndirect displays with host choosers simultaneously.
Determines the maximum number of remote display connections which will be managed simultaneously. I.e. the total number of remote displays that can use your host.
When GDM is ready to manage a display an ACCEPT packet is sent to it containing a unique session id which will be used in future XDMCP conversations.
GDM will then place the session id in the pending queue waiting for the display to respond with a MANAGE request.
If no response is received within MaxWait seconds, GDM will declare the display dead and erase it from the pending queue freeing up the slot for other displays.
The MaxWaitIndirect parameter determines the maximum number of seconds between the time where a display requests a chooser and completion of protocol negotiation. If the timeout is exceeded, GDM will remove the display from the pending list freeing up the slot for other displays.
The UDP port number gdm should listen to for XDMCP requests. Don't change this unless you know what you're doing.