Difference between revisions of "X2Go"

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[[Category:Networking]]
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[[Category:Remote desktop]]
== Description ==
+
[[ja:X2Go]]
 +
[[zh-CN:X2Go]]
 +
[http://wiki.x2go.org X2Go] enables you to access a graphical desktop of a computer over the network. The transmission is done using the [[Secure Shell]] protocol, so it is encrypted.
 +
{{Note|X2Go isn't compatible with all desktop environments. You can check [http://wiki.x2go.org/doku.php/doc:de-compat X2Go desktop environment compatibility] first, especially if you want to shadow your current desktop.}}
  
With x2go you can access your desktop using another computer -- that means both LAN and internet connections. The transmission is done using the ssh protocol, so it is encrypted. By using the free nx libraries from NoMachine, a very acceptable performance in both speed and responsiveness is achieved. Even an ISDN connection runs smoothly.
+
== Installation ==
  
This makes it is possible to connect your laptop to any computer with the environment, applications, and performance of the remote desktop. It is also possible to have a bunch of computers connected to a single server (terminal-server, thin-client).
+
Two parts are available in [[official repositories]]. They can be [[Pacman|installed]] with the following packages:
 +
* {{Pkg|x2goserver}} - X2Go server
 +
* {{Pkg|x2goclient}} - X2Go client based on Qt4
  
Clients are available for Linux (Qt4), Windows, and Mac.  The latter two can be downloaded directly as binary from the x2go homepage.
+
== Server configuration ==
  
== x2go and Arch Linux ==
+
=== Configure Secure Shell daemon ===
  
Arch Linux x2go packages are available in the AUR. Currently the server and clients are available. The LDAP based usermanagement suite is not yet finished, nor are tools that make x2go more convenient for use in schools and thin client environments.
+
X2Go uses [[Secure Shell]] in order to work, so you need to configure sshd daemon to allow X11 forwarding and then start it first. Follow the instructions at [[Secure Shell#X11 forwarding]] and [[Secure Shell#Managing the sshd daemon]].
  
== Installation and configuration ==
+
If you are using other than POSIX (C) locale, you may want to add the following line to [[Secure Shell#Daemon|configuration file]]
 +
# Allow client to pass locale environment variables
 +
AcceptEnv LANG LC_*
  
=== Configuring the Server ===
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=== Load fuse kernel module ===
'''Install the x2goserver package:'''<br>
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Install x2goserver from AUR (manually, with use of yaourt or other tools).
+
  
'''Install the ssh-daemon:'''<br>
+
In order for the server to be able to access files on the client computer you should load a {{ic|fuse}} [[kernel module]].
pacman -S openssh
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/etc/rc.d/sshd start
+
  
To have sshd started at boot time, you have to put it into the daemeons line in
+
=== Setup SQLite database ===
/etc/rc.conf, e.g.
+
Run the following command on the server to initialize the SQLite database (which is required in order for the x2go server to work):
 +
# x2godbadmin --createdb
  
DAEMONS=(... network ... sshd ...)
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=== Start X2Go server daemon ===
  
'''Load the fuse module:'''<br>
+
Now all you need to do is [[start]] {{ic|x2goserver.service}}.
This makes it possible for the server to access files on the client computer.
+
  
modeprobe fuse
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== Desktop Shadowing ==
  
To have this module loaded at boot time, you also have to put it into the MODULES line in /etc/rc.conf, e.g.
+
To gain access to the "local desktop" (as opposed to a unique session/desktop environment) you need to install {{Aur|x2godesktopsharing}} from the [[AUR]]. Then, launch {{ic|x2godesktopsharing}}.
  
'''Initialize the SQL database (and start the SQL server):'''
+
Note, you do not need x2godesktopsharing to access "local desktop" of user "foo" by user "foo". x2godesktopsharing is for accessing "foo"'s desktop by "foo2" user. Just choose "Connection to local desktop" in "session type" in x2goclient.
  
You can choose to use either Postgres or SQLite database, the latter does not need a running server.
+
== Client configuration ==
  
Initialize SQLite db:
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Make sure you can open a ssh-session from the client to the server
  x2godbadmin --createdb
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  ssh username@host
  
Start the x2goserver:
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Then run X2Go client itself
  /etc/rc.d/x2goserver start
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  x2goclient
  
If you want to have this services started at boot time, include them in the DAEMONS line in /etc/rc.conf
+
You can now create several sessions, which then appear on the right side and can be selected by a mouse click. Each entry consists of your username, hostname, IP, and port for SSH-connection. Furthermore you can define several speed profiles (coming from modem up to LAN) and the desktop environment you want to start remotely.
 
+
DAEMONS=(... network ... sshd ... x2goserver)
+
 
+
'''Check SSH daemon configuration to allow non-English session:'''
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+
If you are using other than POSIX (C) locale, you may want to add the following line to /etc/ssh/sshd_config:
+
 
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# Allow client to pass locale environment variables
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AcceptEnv LANG LC_*
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Then, restart the daemon (as root):
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/etc/rc.d/sshd restart
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+
== Configuration of the Client ==
+
 
+
'''Install the client:'''<br>
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X2goclient is available in AUR. It is a Qt GUI app, although you can also check-out the command line options by running
+
 
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x2goclient --help
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'''Double check ssh'''<br>
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Convince yourself that you can open a ssh-session from the client to
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the server (host).
+
 
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ssh YourUsername_onServer@yourhost_or_ip
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Within the local network this should not be a problem. The way you
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connect from beyond your network, lets say the internet, to your
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comuter at home is a question of how your network is build up. This
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would go beyond the scope of this article. Therefore here only a few
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items:
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* A port has to be opened at the router resp. gateway which forwards requests to your server, and there especially to the sshd-port (which normally is 22). To prevent a big part of the portscan attacks it is probably better to have 222 as publicly reachable port.
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* To prevent you from having the need to keep your public IP address in mind (especially if this changes dynamically) it is advisable to use a dynamic DNS-Service (DynDNS, DynIP). Many routers are preconfigured to be reachable under a name rather than an IP address.
+
 
+
'''Enough preliminaries! Now to the x2goclient. Run it:'''<br>
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x2goclient
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This opens the client application. You can now create several sessions, which then appear on the right side and can be selected by a mouseclick. Each entry consists of your username on the server, hostname and IP and the port for ssh-connection. Furthermore you can define several speed profiles (coming from modem up to LAN) and the desktop environment you want to start remotely.
+
  
'''Common mistakes:'''<br>
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'''Common mistakes:'''
 
Do not simply choose the defaults of KDE or Gnome, since the executables startkde or startgnome are usually not in the PATH when logging in using ssh. Use full paths to startkde or
 
Do not simply choose the defaults of KDE or Gnome, since the executables startkde or startgnome are usually not in the PATH when logging in using ssh. Use full paths to startkde or
 
startgnome. You can also start openbox or another window manager.  
 
startgnome. You can also start openbox or another window manager.  
  
You should be asked for your password for your user at the server now and after login you will see the x2go logo for a short time, and -- voila -- the desktop.
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You should be asked for your password for your user at the server now and after login you will see the X2Go logo for a short time, and -- voila -- the desktop.
  
'''Exchange data between client and server(desktop)'''<br>
+
'''Exchange data between client and server(desktop)'''
 
On the x2goclient (e.g. laptop) local directories could be shared. The server will use fuse and sshfs to access this directory and mount it to a subdirectory media
 
On the x2goclient (e.g. laptop) local directories could be shared. The server will use fuse and sshfs to access this directory and mount it to a subdirectory media
 
of your home directory on the server. This enables you to have access to laptop data on your server or to exchange files. It is also possible to mount these shares
 
of your home directory on the server. This enables you to have access to laptop data on your server or to exchange files. It is also possible to mount these shares
 
automatically at each session start.
 
automatically at each session start.
  
'''To leave a session temorarily'''<br>
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'''To leave a session temporarily'''
Another special feature of x2go is the possibility of suspending a session. This means you can leave a session on one client and reopen
+
Another special feature of X2Go is the possibility of suspending a session. This means you can leave a session on one client and reopen
 
it  even from another client  at the same point. This can be used to to start a session in the LAN and to reopen it later on a laptop.
 
it  even from another client  at the same point. This can be used to to start a session in the LAN and to reopen it later on a laptop.
The session data are stored and administrated in a potges databse on the server in the meanwhile. The state of the sessions is protocolled
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The session data are stored and administered in a postgres database on the server in the meanwhile. The state of the sessions is protocolled
 
by a process named x2gocleansessions.
 
by a process named x2gocleansessions.
  
Line 104: Line 70:
 
'''Workaround for failing compositing window manager for remote session'''
 
'''Workaround for failing compositing window manager for remote session'''
  
This is useful for situations, when the computer running x2gserver is used also for local sessions with e.g. compiz as the window manager. For remote connections with x2goclient, compiz fails to load and metacity should be used instead. The following is for GNOME, but could be modified for other desktop environments. (Getting compiz ready is not part of this how-to.)
+
This is useful for situations, when the computer running x2goserver is used also for local sessions with e.g. compiz as the window manager. For remote connections with x2goclient, compiz fails to load and metacity should be used instead. The following is for GNOME, but could be modified for other desktop environments. (Getting compiz ready is not part of this how-to.)
  
 
Create /usr/local/share/applications/gnome-wm-test.desktop:
 
Create /usr/local/share/applications/gnome-wm-test.desktop:
Line 135: Line 101:
 
  $ gconftool-2 --type string --set /desktop/gnome/session/required_components/windowmanager "gnome-wm-test"
 
  $ gconftool-2 --type string --set /desktop/gnome/session/required_components/windowmanager "gnome-wm-test"
  
== Future ==
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== Troubleshooting ==
  
At the moment the package consists mainly of the x2goserver and the x2goclient. It is planned to add in near future:
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=== Authentication error ===
* LDAP-Integration. This allow the administration of users, sessions and logins using LDAP. This is an interesting feature for schols or companys. For this purpose there are control programs which integrate themselves into the KDE Control Center.
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* The option to use x2goclient as a login screen for thin clients.
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* The possibility to use locale devices (CD, floppy, USB-stick) remotely and transparently.
+
  
Questions and problems? You could contact me also directly.
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If the following error appears:
[[Special:Emailuser/Gerbra|GerBra]]
+
  
(Many thanks to Stefan Husmann for translation from archlinux.de wiki)
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Authentification Failed:
 +
The host key for this server was not found but an othertype of key exists.
 +
An Attacker might change the default server key to confuse 
 +
your client into thinking the key does not exist
  
== Links ==
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Delete the servers entry from {{ic|~/.ssh/known_hosts}} file and retry to authenticate.
 +
 
 +
=== No selection screen in x2goclient ===
 +
 
 +
A regression in {{Pkg|iproute2}} causes ''ss'' to show no result when specifying the {{ic|-u}} flag, as done in {{ic|/usr/bin/x2golistdesktops}}. [https://marc.info/?l=linux-netdev&m=143018447007958&w=2]
 +
 
 +
See [http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=799], [https://bbs.archlinux.org/viewtopic.php?pid=1541035] for more information.
  
[http://wiki.archlinux.de/?title=Bild:X2go-1.png Screenshot KDE-Session]
+
=== Sessions do not logoff correctly ===
  
[http://wiki.archlinux.de/?title=Bild:X2go-2.png Screenshot configuration dialog]
+
Due to [http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=914 this bug] the X2Go sessions might not logoff correctly. The script that initiates the session spits out many log lines that might confuse X2go. A simple workarround is to create a custom session script and redirect the log output either to a file or to {{ic|/dev/null}} and then point your X2Go-client to this custom script.
 +
 
 +
Here is a sample script for an XFCE session:
 +
 
 +
  #!/bin/sh
 +
  #
 +
  #xfce4-session spits out quite a bit of text during logout, which I guess
 +
  #confuses x2go so we would get a black screen and session hang.
 +
  #adding redirect to a logfile like "~/logfile" or "/dev/null" nicely solved it
 +
  # see http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=914
 +
  /usr/bin/xfce4-session > /dev/null
 +
 
 +
=== Shared folders do not mount (Windows Clients) ===
 +
The ssh-daemon used by the X2go windows client uses depreceated ssh-dss keys by default and because Arch does not accept them your shared folders will not mount. Check out this [http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=1009 bug report] for more information.
 +
 
 +
This can be solved on the windows side by generating different type of key:
 +
 
 +
  C:\Program Files (x86)\x2goclient\ssh-keygen -b 2048 -t rsa
 +
 
 +
And simply replace {{ic|c:\Users\User\.x2go\etc\ssh_host_dsa_key}} and {{ic|c:\Users\User\.x2go\etc\ssh_host_dsa_key.pub}} with the newly generated key files.
 +
 
 +
Other workarrounds from [http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=1009] might help, too.
 +
 
 +
== Links ==
  
[http://x2go.berlios.de Project page]
+
* [http://wiki.archlinux.de/?title=Bild:X2go-1.png Screenshot KDE-Session]
 +
* [http://wiki.archlinux.de/?title=Bild:X2go-2.png Screenshot configuration dialog]
 +
* [http://x2go.org Project page]

Latest revision as of 16:04, 27 June 2016

X2Go enables you to access a graphical desktop of a computer over the network. The transmission is done using the Secure Shell protocol, so it is encrypted.

Note: X2Go isn't compatible with all desktop environments. You can check X2Go desktop environment compatibility first, especially if you want to shadow your current desktop.

Installation

Two parts are available in official repositories. They can be installed with the following packages:

Server configuration

Configure Secure Shell daemon

X2Go uses Secure Shell in order to work, so you need to configure sshd daemon to allow X11 forwarding and then start it first. Follow the instructions at Secure Shell#X11 forwarding and Secure Shell#Managing the sshd daemon.

If you are using other than POSIX (C) locale, you may want to add the following line to configuration file

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

Load fuse kernel module

In order for the server to be able to access files on the client computer you should load a fuse kernel module.

Setup SQLite database

Run the following command on the server to initialize the SQLite database (which is required in order for the x2go server to work):

# x2godbadmin --createdb

Start X2Go server daemon

Now all you need to do is start x2goserver.service.

Desktop Shadowing

To gain access to the "local desktop" (as opposed to a unique session/desktop environment) you need to install x2godesktopsharingAUR from the AUR. Then, launch x2godesktopsharing.

Note, you do not need x2godesktopsharing to access "local desktop" of user "foo" by user "foo". x2godesktopsharing is for accessing "foo"'s desktop by "foo2" user. Just choose "Connection to local desktop" in "session type" in x2goclient.

Client configuration

Make sure you can open a ssh-session from the client to the server

ssh username@host

Then run X2Go client itself

x2goclient

You can now create several sessions, which then appear on the right side and can be selected by a mouse click. Each entry consists of your username, hostname, IP, and port for SSH-connection. Furthermore you can define several speed profiles (coming from modem up to LAN) and the desktop environment you want to start remotely.

Common mistakes: Do not simply choose the defaults of KDE or Gnome, since the executables startkde or startgnome are usually not in the PATH when logging in using ssh. Use full paths to startkde or startgnome. You can also start openbox or another window manager.

You should be asked for your password for your user at the server now and after login you will see the X2Go logo for a short time, and -- voila -- the desktop.

Exchange data between client and server(desktop) On the x2goclient (e.g. laptop) local directories could be shared. The server will use fuse and sshfs to access this directory and mount it to a subdirectory media of your home directory on the server. This enables you to have access to laptop data on your server or to exchange files. It is also possible to mount these shares automatically at each session start.

To leave a session temporarily Another special feature of X2Go is the possibility of suspending a session. This means you can leave a session on one client and reopen it even from another client at the same point. This can be used to to start a session in the LAN and to reopen it later on a laptop. The session data are stored and administered in a postgres database on the server in the meanwhile. The state of the sessions is protocolled by a process named x2gocleansessions.

Various

Workaround for failing compositing window manager for remote session

This is useful for situations, when the computer running x2goserver is used also for local sessions with e.g. compiz as the window manager. For remote connections with x2goclient, compiz fails to load and metacity should be used instead. The following is for GNOME, but could be modified for other desktop environments. (Getting compiz ready is not part of this how-to.)

Create /usr/local/share/applications/gnome-wm-test.desktop:

[Desktop Entry]
Type=Application
Encoding=UTF-8
Name=gnome-wm-test
Exec=/usr/local/bin/gnome-wm-test.sh
NoDisplay=true

Create script /usr/local/bin/gnome-wm-test.sh:

#!/bin/sh
# Script for choosing compiz when possible, otherwise metacity
# Proper way to use this script is to set the key to mk-gnome-wm
# /desktop/gnome/session/required_components/windowmanager
xdpyinfo 2> /dev/null | grep -q "^ *Composite$" 2> /dev/null
IS_X_COMPOSITED=$?
if [ $IS_X_COMPOSITED -eq 0 ] ; then
    gtk-window-decorator &
    WM="compiz ccp --indirect-rendering --sm-client-id $DESKTOP_AUTOSTART_ID"
else
    WM="metacity --sm-client-id=$DESKTOP_AUTOSTART_ID"
fi
exec bash -c "$WM"

Modify the following gconf key to start the session with gnome-wm-test window manager:

$ gconftool-2 --type string --set /desktop/gnome/session/required_components/windowmanager "gnome-wm-test"

Troubleshooting

Authentication error

If the following error appears:

Authentification Failed:
The host key for this server was not found but an othertype of key exists.
An Attacker might change the default server key to confuse  
your client into thinking the key does not exist

Delete the servers entry from ~/.ssh/known_hosts file and retry to authenticate.

No selection screen in x2goclient

A regression in iproute2 causes ss to show no result when specifying the -u flag, as done in /usr/bin/x2golistdesktops. [1]

See [2], [3] for more information.

Sessions do not logoff correctly

Due to this bug the X2Go sessions might not logoff correctly. The script that initiates the session spits out many log lines that might confuse X2go. A simple workarround is to create a custom session script and redirect the log output either to a file or to /dev/null and then point your X2Go-client to this custom script.

Here is a sample script for an XFCE session:

 #!/bin/sh
 #
 #xfce4-session spits out quite a bit of text during logout, which I guess
 #confuses x2go so we would get a black screen and session hang.
 #adding redirect to a logfile like "~/logfile" or "/dev/null" nicely solved it
 # see http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=914
 /usr/bin/xfce4-session > /dev/null

Shared folders do not mount (Windows Clients)

The ssh-daemon used by the X2go windows client uses depreceated ssh-dss keys by default and because Arch does not accept them your shared folders will not mount. Check out this bug report for more information.

This can be solved on the windows side by generating different type of key:

 C:\Program Files (x86)\x2goclient\ssh-keygen -b 2048 -t rsa

And simply replace c:\Users\User\.x2go\etc\ssh_host_dsa_key and c:\Users\User\.x2go\etc\ssh_host_dsa_key.pub with the newly generated key files.

Other workarrounds from [4] might help, too.

Links