HOWTO: Set up VNC server with resumable sessions

[Tichondrius]

Okay, so this setup will allow me to start a new session on display 1. But can I resume an existing session on my physical display 0? Let's say I start a session at home normally on display 0. I start up gaim and firefox then lock the screen and go over to a friend's place. Can I resume this session using this method, or only start a new session?

Ok, to resume a session you started on your physical display (display :0) all you really need is to turn on Ubuntu's remote desktop feature using the Remote Desktop Preferences dialog box accessible from System->Preferences->Remote Desktop menu item. Just check the first two options there (allow other users to view your desktop and allow other users to control your desktop) and set the password in the bottom of the dialog box (check the REuqire password option), and you're done !
The above uses the built in VNC capability that Ubuntu comes installed with, but the drawback is that it's a little slow, and you need to enable it for each user which wants to allow his desktop to be view or controlled remotely. Also this doesn't allow remote VNC clients to log in to GDM, only to view a GDM session that was started by someone actually using the physical display. So if currently no one is logged in, a remote user cannot connect to display :0 and start a new session.
But don't worry - there is a better way which allows you to view the phyical display remotely and also log-in to a new session from GDM (using a remote VNC client) ! And it works faster (as fast as the regular VNC server), and works for all users. Here's how to do that :

1. Install x11vnc package

sudo apt-get install x11vnc

2. Add x11vnc service to xinetd:

sudo gedit /etc/xinetd.d/x11vnc

Enter this into the new file:

service x11vnc
{
        port            = 5900
        type            = UNLISTED
        socket_type     = stream
        protocol        = tcp
        wait            = no
        user            = root
        server          = /usr/bin/x11vnc
        server_args     = -inetd -o /var/log/x11vnc.log -display :0 -auth /var/lib/gdm/:0.Xauth -many -bg
        disable         = no
}

3. Restart xinetd (usually there is no need to reboot, but occasionally it might be required)

sudo /etc/init.d/xinetd stop
sudo killall Xvnc
sudo killall x11vnc
sudo /etc/init.d/xinetd start

4. From a remote machine use your VNC client to connect to display :0

vncviewer  vnchost:0

Note that after loggging from GDM and also after logging out from the X-session back and going back to GDM, the VNC client gets disconnected for some reason. So you just need to re-connect and you will get back into the session you logged into. When logging out, the disconnect happens when gnome asks you to confirm your intention to log out, so it's best to turn off the log-out confirmation dialog box by going to System->Preferences->Sessions and un-checking the "ask on logout" option.

Please tell me how this works out for you....I plan to add this to the HOWTO

[_kk]

Tichondrius, the x11vnc guide worked flawlessly for me. Easy peasy

It's a bit faster than the buildin vnc but still not as fast as FreeNX, that I've tried too.

BTW, how do I change my screen resolution? Right now I get a tiny 640x480 display. If I go to System > Preferences > Screen Resolution I can see my current settings but I can't change them.

It's the same when I use the bulidin vnc. It happend after I unplugged the monitor from the box. I run the box all remotely and thus have no monitor connected.

[Tichondrius]

Your resolution is low because xorg X-server chooses the resolution based on the monitor capabilities which are dynamically communicated to the machine when X starts up. There is a way to override that, in the xorg.conf file but I don't remember exactly how. Just thought I give you a direction to search.

[simon0t7]

That looks good.
Check to see if any files in your home directory have suddenly changed to root ownership. If any have, let us know which ones. If none have, try the following:

sudo /etc/init.d/xinetd stop

sudo killall Xvnc

sudo /etc/init.d/xinetd start

sudo /etc/init.d/gdm restart

That will kill the xinet daemon, kill all Xvnc processes, restart xinet daemon and restart the GDM. See if that lets you login again.

When I screwed up with the root password, after I reclaimed ownership of the file, I had to do the above steps before I could login on the console GDM.

I have had a few quirks since then, but luckily I have ssh access for remote logins setup. Even if the console goes kerblewey, I can still use the SSH login... And yes, it happened that the keyboard was not accessable due to a motherboard port failure. SSH allowed me to get in and shut it down cleanly so I could changed the motherboard.

See if that helps.

I'll have to try that. I just moved my /home to a different hard dirve but it doesn't auto-mount in fstab so i gotta see what's up with that first. No home = no X
I'll keep you posted

[_kk]

Your resolution is low because xorg X-server chooses the resolution based on the monitor capabilities which are dynamically communicated to the machine when X starts up. There is a way to override that, in the xorg.conf file but I don't remember exactly how. Just thought I give you a direction to search.

Thank you for letting me know. Actually I have already been looking in the xorg.conf but I wasn't sure if that was the way to go. Now i'll just have to dig deeper.

Update: I got it to work nicely after some xorg.conf editing. Disabling the loading of 'dcc' and making a modeline for my screen did the trick.

[dermotti]

You guys really should give FreeNX a try, its wayyyyy better than vnc, Much faster and works out the box...

[Tichondrius]

You guys really should give FreeNX a try, its wayyyyy better than vnc, Much faster and works out the box...

well, I did set up FreeNX as well, but I couldn't get resuming sessions to work - that is, I had to start a new session every time. Also sometimes it would go nuts and spawn many processes on the server, occupying the CPU 100%. So in my experience it wasn't as reliable and flexible as VNC, but I agree it was faster.

[_kk]

You guys really should give FreeNX a try, its wayyyyy better than vnc, Much faster and works out the box...

It's installed and running but have the same problem as Tichondrius. I can't resume sessions properly from windows... I googled the problem and found that apparently it's a know bug when connecting from a win client. Such a shame because as you say it's very nice and fast.

[Tichondrius]

Well not being able to resume sessions from windows pretty much ruins it for me as a possible alternative to VNC. And btw I wouldn't call this a "known bug", I'd call this a crippling problem which undermines the usefulness of the whole app.

[_kk]

There's no problem in a linux => linux setup but using a win client makes this flaw appear. And I totally agree, it renders the app useless. Sadly, that is the same conclusion many others are making on the freenx mailing list: http://mail.kde.org/pipermail/freenx-knx/