Guacamole

From Linuxintro
Revision as of 19:05, 24 November 2015 by imported>ThorstenStaerk (Reverted edits by 188.143.234.155 (talk) to last revision by ThorstenStaerk)


A Linux desktop in a browser

Overview

Guacamole is a program to control a Linux desktop over the network in a browser.

Sometimes in your Linux life, you need to control your servers in the internet with a graphical user interface. This is tedious when you are behind a corporate firewall blocking ssh requests to the public internet. Typical corporate firewalls only allow proxified client access to port 80, 8080 and 443 in the public internet. One way to go is to use a browser to display a Linux desktop. The solution is guacamole.

Quickstart

This will show you

  • how to install guacamole 0.9.3 on Ubuntu (tested with 14.04)
  • how to make this configuration survive a reboot
  • how to secure transmission with SSL
  • how to make the website accessible from behind a firewall (port 80 or 443)

Here's what you do as root user:

  • install software that we will need later:
apt-get update
apt-get install tomcat6 tightvncserver gcc make xterm

configure VNC server

Guacamole does the communication between a VNC server and the web browser. So whatever you see in VNC will be in the browser. In this example let's use xfce as desktop environment:

  • install xfce:
apt-get install xfce4
  • activate gnome for your VNC:
cd
mkdir .vnc
cat >> .vnc/xstartup <<EOF
#!/bin/sh
xfce4-session || xterm
EOF
chmod 777 .vnc/xstartup

deploy guacamole client

# mv guacamole-0.9.3.war /var/lib/tomcat6/webapps/
  • surf to http://localhost:8080/guacamole-0.9.3. A folder /var/lib/tomcat6/webapps/guacamole-0.9.3 will be created with some content. We will need that later.
  • although login is not yet possible your browser will show a login screen like that:

Guacamole-login.png

install guacamole server

  • install some dependencies that the server will need to build with vnc support:
apt-get install libvncserver-dev libpng-dev libcairo-dev

tar xvzf guacamole-server-0.9.3.tar.gz
  • build the server:
cd guacamole-server-0.9.3
./configure && make -j8 && make install
  • the following step is ugly; installation and binary do not completely fit so we must do that:
ln -s /usr/local/lib/libguac.so* /lib
ln -s /usr/local/lib/libguac-client-vnc.so* /lib/
  • now we start the guacamole daemon:
# guacd
guacd[17669]: INFO:  Guacamole proxy daemon (guacd) version 0.9.3
guacd[17669]: INFO:  Successfully bound socket to host ::1, port 4822
guacd[17669]: INFO:  Exiting and passing control to PID 17671
root@tstaerk-desktop:/var/log# guacd[17671]: INFO:  Exiting and passing control to PID 17672

configure guacamole

  • create a folder for guacamole's configuration:
mkdir /etc/guacamole
  • create a file /etc/guacamole/guacamole.properties with the content
# Hostname and port of guacamole proxy
guacd-hostname: localhost
guacd-port:     4822

# Location to read extra .jar's from
lib-directory:  /var/lib/tomcat6/webapps/guacamole-0.9.3/WEB-INF/classes

# Authentication provider class
auth-provider: net.sourceforge.guacamole.net.basic.BasicFileAuthenticationProvider

# Properties used by BasicFileAuthenticationProvider
basic-user-mapping: /etc/guacamole/user-mapping.xml
  • create a file /etc/guacamole/user-mapping.xml with the content
<user-mapping>
   <authorize username="user" password="password">
      <protocol>vnc</protocol>
         <param name="hostname">localhost</param>
         <param name="port">5901</param>
         <param name="password">password</param>
    </authorize>
</user-mapping>

configure tomcat

  • find out your tomcat's user directory:
# cat /etc/passwd|grep tomcat
tomcat6:x:113:116::/usr/share/tomcat6:/bin/false
in this case it is /usr/share/tomcat6
  • create a folder .guacamole in your tomcat's user directory:
mkdir /usr/share/tomcat6/.guacamole
  • link guacamole.properties into your tomcat's user directories' guacamole folder
ln -s /etc/guacamole/guacamole.properties /usr/share/tomcat6/.guacamole

finishing

  • start a vnc server, as password set password (the vnc password given in user-mappings.xml)
vncserver
  • restart your tomcat server
/etc/init.d/tomcat6 restart

Guacamole-after-login.png

Now when you click on "Default" you will see your VNC desktop in your browser.

  • next steps: SSL
  • next steps: proxypass

Persist it

Add the following line to /etc/crontab: 

@reboot root /usr/local/sbin/guacd &

TroubleShooting

invalid login

  • now the problem is that tomcat does not know where to find the Authentication class:

/var/lib/tomcat6/webapps/guacamole/WEB-INF/classes/net/sourceforge/guacamole/net/basic/BasicFileAuthenticationProvider.class

is not in /etc/guacamole/guacamole.properties

  • so add it
  • cat /etc/passwd gives me a line
tomcat6:x:113:116::/usr/share/tomcat6:/bin/false

ll /usr/share/tomcat6/.guacamole/
total 8
drwxr-xr-x 2 root root 4096 Nov 26 07:58 ./
drwxr-xr-x 6 root root 4096 Nov 26 07:57 ../
lrwxrwxrwx 1 root root   35 Nov 26 07:58 guacamole.properties -> /etc/guacamole/guacamole.properties
  • works now. So the thing is:
    • take care that it is called guacamole and not guacamole-0.8.3 (sure?)
    • make sure the classpath in /etc/guacamole/guacamole.properties is correct, e.g.
# Location to read extra .jar's from
lib-directory:  /var/lib/tomcat6/webapps/guacamole/WEB-INF/classes

Server error

  • now I got a server error so I straced guacd:
strace -p 15332

and saw 

[pid 20344] open("/usr/lib/x86_64-linux-gnu/libguac-client-vnc.so", O_RDONLY) = -1 ENOENT (No such file or directory)

so the problem is that libguac-client-vnc.so is missing.

  • downloaded java version 1.7.45 and compiled guacamole-client using mvn. But there was no *.so* file in it
  • so installed libvncserver-dev and rebuild and reinstalled guacamole-server
  • and there it is, libguac-client-vnc.so
  • now the error message changed from "server error" to "unauthorized"

Failed to load

When logging in I got an error message 

Failed to execute 'send' on 'XMLHttpRequest': Failed to load 'http://162.209.103.145:8080/guacamole-0.8.3/login'.

Solution was to: 

/etc/init.d/tomcat6 restart

Error initializing VNC client

After logging in I got the error message 

Error initializing VNC client

Solution was to start 

vncserver

Could not connect

If you surf to the page and get an error message like 

Unable to connect

It probably means that tomcat is not running. It must be possible to connect to port 8080, a java process for tomcat must be running. 

/etc/init.d/tomcat6 status

must deliver something like 

* Tomcat servlet engine is running with pid 17546

See also

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