vincentkong.com » Ubuntu

Running VirtualBox in Ubuntu

Vincent Kong — Mon, 28 Dec 2009 08:09:15 +0000

To install VirtualBox in Ubuntu

$ sudo apt-get install virtualbox-ose

To run VirtualBox type

$ /usr/bin/VirtualBox

: VirtualBox in Xubuntu

Running GUI Software from Remote Servers with Xming

Vincent Kong — Thu, 29 Oct 2009 03:50:31 +0000

Xming provides an implementation of the X Windows System (X11 server) for Microsoft Windows. Its useful when needing to use a GUI application on a remote server that doesn’t provide remote desktop access.

Installing Xming

Installing Xming on Windows is easy; download the binary file and follow the installation wizard.

To configure Xming run XLaunch from the Start Menu, otherwise run Xming to start up the application.

When started an icon would appear on the taskbar.

Configure X11 Forwarding in PuTTY

Before establishing and SSH connection go to Connection -> SSH -> X11 in the configuration window and check the “Enable X11 forwarding” box.

PuTTY X11 Forwarding

After SSH connection has been established any GUI application can be run by executing it from the command prompt e.g. the Thunar file manager for Xubuntu

Running Thunar in Windows with Xming

More detail information can be found here.

Installing BoutDuTunnel Server on Mono XSP

Vincent Kong — Fri, 05 Jun 2009 21:43:37 +0000

In my previous blog I talked about setting up a HTTP tunnel using BoutDuTunnel. To setup the server-side, a command line application was used: BdtServer. BoutDuTunnel also provides a web application solution BdtWebServer which lets you host the application inside a web server. To host BdtWebServer in Ubuntu, BoutDuTunnel recommends to use Apache/mod_mono, however I decided to use an alternative approach.

Configuring BdtWebServer

Mono XSP is a lightweight and simple webserver written in C# which runs run ASP.NET applications.

To install Mono XSP run the following:

$ apt-get install mono-xsp2
$ apt-get install libmono-system-runtime2.0-cil

To ensure that XSP is properly installed you can install the ASP.NET 1.1 and 2.0 demo pages.

$ apt-get install asp.net2-examples
$ xsp2 --applications /:/usr/share/asp.net2-demos

When the server has successfully started, point your browser to http://localhost:8080 (the default port for XSP web server is 8080) to display the web page below:

ASP.NET Examples

If the following error is encountered:

System.InvalidOperationException: Standard output has not been redirected or process has not been started.

Run the following command to address the issue:

ln -s /usr/bin/gmcs2 /usr/bin/gmcs

Now the BdtWebServer is ready to be started:

xsp2 --port 8080 --nonstop --applications /:/opt/bdt.bin.1.4.3066.mono/BdtWebServer

--nonstop don’t stop the server by pressing enter. Must be used when the server has no controlling terminal.

Configuring BdtClient

Setting up the BdtClient to establish a connection to BdtWebServer is similar to BdtServer with the exception that the name attribute is set to BdtServer.soap in the service tag of the configuration file.

Security Issue

When hosting the BdtWebServer application in a web server the BdtServerCfg.xml (which contains the username and passwords) will be exploit when you point the web browser http://my.server:8080/BdtServerCfg.xml.

To address this issue I setup XSP to integrate with Apache/mod_proxy by configuring the following Apache configuration to forbid access to BdtServerCfg.xml

    
        Order deny,allow
        Deny from all
    

    
        Order deny,allow
        Allow from all
    
    ProxyRequests off
    ProxyPass / http://localhost:8080/
    ProxyPassReverse / http://localhost:8080/

Finally, I setup a firewall to block port 8080 from public access.

Building Mono from Source

Vincent Kong — Sun, 31 May 2009 03:45:18 +0000

Installing Mono on Ubuntu is easy:

$ apt-get install mono-2.0-devel

Unfortunately even the latest version of Ubuntu 9.04 only comes with Mono 2.0.1. To install a newer (or different) version a solution would be to build Mono from source.

Download the desire version from the Mono website and extract the packaged file.

$ wget http://ftp.novell.com/pub/mono/sources/mono/mono-2.4.tar.bz2
$ tar -xf mono-2.4.tar.bz2

To compile and install Mono execute the following

$ cd mono-2.4
$ configure --prefix=/opt/mono-2.4

Where --prefix option indicates which directory to installation should be; for more option run

$ configure --help

If anything is missing from the system, configure will throw an error, install the missing package with apt-get and try running it again. Then execute the compilation and installation to complete the build.

$ make
$ make install

Compiling Error with Mono 1.9.1

If you are compiling Mono 1.9.1 the following error might be encountered:

wapi_glob.c: In function 'globextend':
wapi_glob.c:303: error: 'ARG_MAX' undeclared (first use in this function)
wapi_glob.c:303: error: (Each undeclared identifier is reported only once
wapi_glob.c:303: error: for each function it appears in.)

The problems is due to the newer versions of GLib no longer defines ARG_MAX. To fix this issue, add the following to mono/io-layer/wapi_glob.c in the Mono source directory:

#include

#if defined(_SC_ARG_MAX)
# if defined(ARG_MAX)
#    undef ARG_MAX
# endif
# define ARG_MAX sysconf (_SC_ARG_MAX)
#endif

#include "wapi_glob.h"

Monitoring Fan RPM in Ubuntu

Vincent Kong — Sat, 30 May 2009 23:12:32 +0000

I have two PWM fan’s installed in my Shuttle KPC K45 being monitor with of sensor-applet in Ubuntu, which also monitors the CPU and hard drive temperature.

To begin run sensors-detect a utility which comes with lm-sensors

$ sudo apt-get install lm-sensors
$ sudo sensors-detect

Answer YES to all the YES/no questions and allow sensors-detect to modify the /etc/modules, and reboot the computer.

To check the status of all the items lm-sensors can read.

$ sensors

To monitor the fan’s RPM from sensor-applet, select it from the “Sensors” tab.

Sensors Applet

Adding a Startup Script in Ubuntu

Vincent Kong — Mon, 12 Jan 2009 13:00:11 +0000

Sometimes there is a script which you wrote that you want to be run each time your system boots up. This was the case when I installed the GNU HTTP Tunnel server to allow SSH through HTTP Proxies for my server.

The easiest way would probably be adding the script the /etc/rc.local file which works simililary to the Windows autoexec.bat file.

But if you want to use best practices then it’s recommend that you put the script in the /etc/init.d directory and run the update-rc.d command against it. A template is also available /etc/init.d/skeleton which you can use to get started.

$ cd /etc/init.d
$ cp skeleton myscript
$ chmod 755 myscript
$ update-rc.d myscript defaults

To remove the start up script in Ubuntu execute the following:

$ update-rc.d myscript remove

Restricting Shell Users to their Home Directory

Vincent Kong — Wed, 07 Jan 2009 13:00:59 +0000

The “easiest way” to lock down users to their home directory is to switch their shell account to rbash (restricted bash). The rbash shell behaves like the bash shell, but some functions are disallowed e.g. change directory with cd.

For more information refer to the man pages for rbash.

$ man rbash

To change the user’s shell modify the file /etc/passwd

$ nano /etc/passwd

and replace /bin/bash with /bin/rbash e.g.

guest:x:100:100::/home/guest:/bin/rbash

Restricting Shell for only SCP/SFTP

Vincent Kong — Fri, 21 Nov 2008 06:28:30 +0000

If you have a server, but only want to allow users to copy files via sFTP without providing shell access. This can be done with rssh, a restricted shell for use with OpenSSH that allows only scp and/or sftp.

To install rssh

$ apt-get install rssh

By default rssh doesn’t allow anything, to allow only sftp modify the rssh.conf file.

$ nano /etc/rssh.conf

Uncomment the line for allowsftp and other transfer protocols you want to enable.

#allowscp allowsftp #allowcvs #allowrdist #allowrsync

To restrict a user to only allow sftp access, modify the /etc/passwd file

$ nano /etc/passwd

For example

ftp:x:100:100::/home/ftp:/usr/bin/rssh

Problem using MySQL JDBC on Tomcat 5.5 and Ubuntu 8.04

Vincent Kong — Wed, 05 Nov 2008 03:36:39 +0000

Normally when I build a web application that connects to a MySQL database, I would place the mysql-connector-java-bin.jar file into the WEB-INF/lib of the web application.

However, when I deployed the application on Tomcat 5.5 on Ubuntu 8.04 I got an exception: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

I couldn’t find the reason which caused the exception, so I did a quick fix by placing the jar file into the Tomcat’s common lib directory.

$ cp mysql-connector-java-bin.jar /usr/share/java $ cd /usr/share/tomcat5.5/common/lib $ ln -s ../../../java/mysql-connector-java-bin.jar mysql-connector-java-bin.jar

Open RAR Files in Ubuntu

Vincent Kong — Wed, 29 Oct 2008 03:07:38 +0000

RAR is a file format developed by Eugene Roshal, and one of the most popular format used for data compression and archiving next to the ZIP file format. By default, Ubuntu doesn’t have any support for extracting RAR files, however there is an available Linux freeware unrar for downloading.

To install unrar in Ubuntu

$ apt-get install unrar

The drawback with this utility is that it only supports the RAR and RAR2 format, but not the RAR3 format which can only be extract by RARLAB’s UnRAR which is not free.